Nitrogen Fertilization

This study was carried out to analyze the spectral reflectance response of different nitrogen levels for corn crops. Four different nitrogen treatments of 0%, 80%, 100% and 120% BMP (best management practice) were studied. Principal component analysis-loading (PCA-loading) was used to identify the effective wavelengths. Partial least squares (PLS) and multiple linear regression (MLR) models were built to predict different nitrogen values. Vegetation indices (VIs) were calculated and then used to build more prediction models. Both full and selected wavelengths-based models showed similar prediction trends. The overall PLS model obtained the coefficient of determination (R 2) of 0.6535 with a root mean square error (RMSE) of 0.2681 in the prediction set. The selected wavelengths for overall MLR model obtained the R 2 of 0.6735 and RMSE of 0.3457 in the prediction set. The results showed that the wavelengths in visible and near infrared region (350-1000 nm) performed better than the two either spectral regions (1001-1350/1425-1800 nm and 2000-2400 nm). For each data set, the wavelengths around 555 nm and 730 nm were identified to be the most important to predict nitrogen rates. The vogelmann red edge index 2 (VOG 2) performed the best among all VIs. It demonstrated that spectral reflectance has the potential to be used for analyzing nitrogen response in corn.

Two field experiments (experiment-1 in 2006 and experiment-2 in 2007) with carrot c.v. 'Kazan F 1 ' were conducted at Trzciana (50 o 06' N, 21 o 85'E) in south-eastern part of Poland. Both of the experiments comprised two sub-blocks with plants: 1. Not receiving foliar nutrition, 2. Receiving foliar nutrition with Pentakeep V -in experiment-1 the plants were sprayed twice and experiment-1 the plants were sprayed once. Each sub-block consisted of the following treatments: 1. Control (without nitrogen fertilization), 2. ½ dose of N as pre-sowing fertilization, 3. Full rate of nitrogen -½ dose of N as a pre-sowing and ½ dose of N as a top dressing fertilization. In 2006 ½ dose of N equaled 100 kg N·ha -1 when in 2007 ½ dose of N equaled 60 kg N·ha -1 .

An experiment was conducted at two locations during spring 2008 at the New Developmental Farm (NDF) and the Cereals Crop Research Institute (CCRI). Two landraces of sweet corn Mansehra (MNS) and Swabi (SWB) were planted with Cv. Azam. Furthermore, four densities and N levels were used in randomized complete block (RCB) design with split-plot arrangement. Phenology, yield and yield components responded positively to locations, landraces, nitrogen and density. Significantly higher number of kernels ear 1 , grain weight and grain yield were found at NDF. Landrace SWB was tasseled and matured late, while Azam was recorded highest for kernel ear-1 (KPE), total grain weight (TGW) and grain yield (GY) followed by SWB. Moreover, days to tasseling and maturity, KPE, TGW, and GY in Nfertilized plots were significantly higher as compared to control. Maximum GY was observed in plots with a density of 100000 plants ha 1 ; however, it was comparable to GY obtained under the dense population of the plants (density of 120000 plants ha 1).

A field experiment was conducted on sandy clay loam soil at agricultural farm, Bapatla during rabi 2002. The study revealed that the availability of nutrients N, P, K and S in soil after harvest were significantly influenced by increased levels of N and S.

Ok, Children of the Corn was true classic from the days when Stephen King was the King of horror. However its true glory lies in marking an era where the Green Revolution has shown its true face as the unlikely Terminator. High-yield strains were developed and seeded everywhere around the world, supplanting most of the old gene pools and agrarian biodiversity since Neolithic Revolution to kingdom come. Especially so in the third or the second world, the Communist East being very much into the same ‘let’s have mutant, pest-resistant, gigantic, super-sweet corn’ wave. In fact, we could argue that much of the Eastern ‘collectivization’ was a more or less a camouflaged fertility cult celebrating chthonian energies, renewal and miraculous hybrids.

Clay minerals are natural materials well known for
their role in retention and persistence of organic and
inorganic compounds in soil. Clay minerals are being
modified through different processes to alter their
charge and surface properties tailored for specific
purposes. Modified clays in general include pillared
layered clays, organoclays, nanocomposites, acid and
salt-induced and thermally and mechanically induced
modified clays. Pillared organoclays and nanocomposites
constitute a novel class of materials, mainly one
kind of modification of expanding 2 : 1 clay minerals.
Acid and salt treatments lead to modification of the
catalytic properties of clays. Clay mineral–polymer
nanocomposites are the hybrids which exhibit a
change in composition and structure on a scale of
nanometres. Modified clay imparts slow-release property
to fertilizers and enhances the water-holding
capacity of soil. Therefore, understanding the methods
of clay modification and properties of modified clays
may facilitate development of agricultural management
systems that ensure long-term sustainability of soil
resources

En el Ecuador desde el siglo XX la intensiva aplicación de fertilizantes químicos, es una de las características de la agricultura en la región Sierra. Esta investigación detectó la lixiviación y volatilización  de dos tipos de fertilizantes nitrogenados en localidades de la Provincia de Pichincha de gran potencial agrícola. Se colectó suelo de tres sitios y se los caracterizó  física y químicamente.  Estos  suelos fueron fertilizados con dos fuentes nitrogenadas: nitrato de amonio y úrea. Para cuantificar la volatilización se fabricaron tres cámaras estáticas cubiertas con plástico, el contenido de amoniaco fue determinado con un indicador de boro 7 días después de su instalación. Para la lixiviación se simuló escorrentía con 300 ml de agua, luego de 48 h el contenido líquido del fondo del envase de cada submuestra fue llevado al espectrofotómetro en el cual se estableció el contenido de nitrógeno total. Se determinó que la úrea lixivia más de 15 ppm en todos los tipos de suelo; en los suelos de textura arcillosa predominantes en el sur-oriente de la provincia no es significativa la volatilización.

This paper presents an exergy and environmental assessment of a 1000 metric t/day ammonia production plant based on the steam methane reforming (SMR) process, including the syngas production, purification (CO 2 capture) and compression units, as well as the ammonia synthesis and purge gas treatment. An integrated heat recovery system produces power and steam at three pressure levels, besides exporting hot water, CO 2 and fuel gas, with no additional heat or power consumption being required. Two configurations for ammonia refrigeration process (À20 C) are compared in terms of power consumption. Exergy cost data for upstream processing stages of natural gas is used to calculate the extended exergy cost of the products of the plant, namely ammonia, CO 2 and fuel gas. Moreover, an appropriated methodology is employed to properly allocate the renewable and non-renewable exergy costs, as well as the CO 2 emissions of the reforming, shift and furnace stack among the products of the plant. By considering that the cost reduction of the combustion gases is a linear function of the exergy flow rate reduction in each component of the heat recovery system, an improved allocation of the CO 2 emission cost along the convection train is performed. A breakdown of the total exergy destruction rate of the plant (136.5 MW) shows that about 59% corresponds to the reforming process followed far behind by the ammonia synthesis and condensation (18.3%) and the gas purification units (13.2%). The overall exergy efficiency of the ammonia plant is calculated as 66.36%, which is enhanced by recovering the hydrogen-rich and fuel gases in the purge gas treatment process. The total and non-renewable exergy costs and CO 2 emission cost of the ammonia produced are calculated as 1.7950 kJ/kJ and 0.0881 kg CO2 /MJ, respectively. In addition, a rational exergy cost of 1.6370 kJ/kJ and CO 2 emission cost of 0.0821 kg CO2 /MJ are allocated to the CO 2 gas, which can be supplied as feedstock to an associated chemical plant (urea, methanol, polymers, etc.).

With the advent of Green Revolution era in the mid-1960s, high-yielding wheat (Triticum aestivum L.) varieties and chemical fertilizers were introduced in South Asia. Fertilizer
consumption is continuously increasing since then, but the productivity of wheat is relatively stagnant during the last decade. In South Asia, fertilizers have been applied to
wheat as blanket recommendations for regions with similar climate and landform. There exists a large variation in nutrient use efficiencies in wheat because of following blanket recommendations for nitrogen, phosphorus, and potassium in fields differing greatly in nutrient-supplying capacity of the soil. Research carried out in South Asia suggests that further improvement in nutrient use efficiency will become possible by balanced use of nitrogen, phosphorus, and potassium fertilizers, and by rational use of organic manures in wheat systems. Long-term fertility experiments also confirm the need of balanced use
of nutrients to produce high sustainable yield levels of wheat. In saline alkali soils, wheat needs to be supplied with higher amounts of nutrients, particularly N, than in normal
soils. Band placement of fertilizers, particularly phosphorus, leads to improved fertilizer use efficiency, but appropriate machinery is lacking. Recently introduced site-specific
nutrient management strategies for wheat take into account field-to-field variability and can help increase fertilizer use efficiency more than that achieved by following blanket
fertilizer recommendations. Conservation agricultural practices consisting of reduced tillage and residue retention in wheat fields have already been introduced in South Asia. Nutrient management strategies for these wheat-growing environments are also being actively worked out. Yield gap analysis shows that productivity of wheat as well as nutrient use efficiencies can be further improved.

SUMMARY Multilocation experiments were established to determine the best strategy for using inorganic fertilizer in conservation agriculture (CA) systems that use green manure cover crops, namely sunhemp, velvet bean and cowpea grown in rotation with maize. The objectives of the study were to determine (i) the effect of half and full rates of basal fertilizer on maize and legume biomass yields, (ii) the residual effects of unfertilized, half and fully fertilized green manure legumes on maize grown after the legumes, and (iii) the residual effect of unfertilized, half and fully fertilized green manure legumes combined with basal and topdressing fertilizer on maize yields. Experimental design was a randomized complete block with basal fertilizer as a treatment in the green manure legumes phase. Previously, in the maize phase, green manure legume species were the main treatment with basal fertilizer as a subtreatment (sunhemp, velvet bean and cowpea: 0, 75, 150 kg ha −1 and 0, 50, 100 kg ha −1 , respectively). Nitrogen was applied in the maize phase at 0, 23, 46, 69 kg N ha −1 as a sub-subtreatment in Malawi. Results showed that inorganic fertilizer is the most effective when applied to the maize, not green manure legumes. Biomass of green manure legumes, sunnhemp 8084 kg ha −1 , velvet bean 7678 kg ha −1 and cowpea 4520 kg ha −1 , was not significantly affected by application of basal fertilizer. Maize production increased after the application of green manure legumes with maize-after-maize, maize-after-velvet bean, maize-after-sunnhemp and maize-after-cowpea, yielding 3804, 5440, 5446 and 5339 kg ha −1 , respectively. Nitrogen increased maize yield regardless of the previously used green manure legumes species. Our results suggest that farmers should apply fertilizer to maize and grow green manure legumes on residual soil in CA systems. Despite growing green manure legumes, smallholders should apply nitrogen topdressing to maize grown using the green manure legumes in some agro-ecologies.

Use of inorganic fertilizers constitutes 20% of the rice production cost in Mwea. Azolla fern, which grows in Mwea Irrigation paddies, has the potential to supplement the nitrogen requirement, thus reducing the fertilizer costs. A field experiment was conducted in Mwea Irrigation Scheme during 2015 long and short rains to determine the effect of Azolla incorporation and inorganic nitrogen on growth and yield of rice. The treatments comprised three nitrogen fertilizer levels (0, 30 and 60kg N ha-1) and three Azolla biomass levels (0, 7.5 and 15tons ha-1) laid out in a randomized complete block design with a split-plot arrangement. Data on plant height and number of tillers per plant were collected at 21, 35, 45, and 65 and 75 days after transplanting rice while yield and yield components were determined at 120 days after transplanting rice. Soil was analysed for N, P and K, before and after termination of the experiment. Data were subjected to analysis of variance using SAS and means separated using the least significant difference test at p ≤ 0.05. Azolla incorporation significantly increased residual soil phosphorus, grain weight, % grain filling and grain yield. Inorganic nitrogen significantly increased plant height, tiller numbers, neck node, and panicle length, number of panicle m-2 and grain yield. Grain yield increase from Azolla treatment ranged from 5 to 42% compared to that of inorganic nitrogen which ranged from 18 to 36%. Application of 15t ha-1 of Azolla biomass recorded the highest yield, however, it was not significantly different from that of 7.5t ha-1 .

Hydroponic growing systems currently employed in agricultural settings are plagued with a problem that traditional (soil) systems are not; which is the inability to effectively utilize ammonia. The reason hydroponic systems are unable to utilize ammonia is because of toxicity. These systems lack the ability to convert ammonia, which quickly builds up, into nitrates. By not being able to convert these readily available fertilizers hydroponic growers are limited in the available nitrogen sources for production. If this problem can be addressed cheaper fertilizers would be more readily available for this adaptable growing system. (Howarth et al.)

Tef is a highly valued crop in the national diet of Ethiopians and the major crops grown in central highlands of Ethiopia. However, its productivity is constrained by low plant-available soil nutrients due to depleting soil organic matter content and long history of intensive cultivation. Therefore, a field experiment was carried out at Debrezeit agricultural research center in Ada’a district during the 2017 main cropping season with the objective of to assessing the effect of N and blended (NPSZnB) fertilizers on yield and yield components of tef, nutrient uptake and verifying economically feasible rates of N and blended NPSZnB fertilizers for high yield of tef production. The experiment consisted four levels of nitrogen (0, 46, 92 and 138 kg N ha -1 ) and five levels of blended (0, 100, 150, 200 and 250 kg NPSZnB ha 1 ) in factorial combinations using Kora tef variety as a test crop. The experiment was laid out in RCBD with three replication. The result revealed that the main effe...

Drought is a multidimensional stress that results in economic mislays. Allometric features of drought stressed cotton plants were investigated during two separate experiments. In the first experiment, susceptibility of the cotton seed germination stage towards decrease osmotic potential was evident under PEG-8000 induced drought stress. While changes in growth and biochemical constituents were studied from the field experiment and were explained on the basis of developmental plasticity under water deficit growth conditions. Potassium nitrate was applied as the seed pre-treatment and its influence on the morphological and structural development was marked with prime reference to cotton growth and productivity under water limited environment. A shift in the biochemical attributes of drought stressed cotton plants showed reduction in the chlorophyll contents occurred. Cotton stress response was obvious from the shift in the chlorophyll a/b relative ratio which was also influenced by seed pre-treatment. It is concluded that structural modifications under water scarce environment play a vital role in determining the morphological and physiological status of cotton.

The objective of the present study was to investigate the comparative roles of nitrogen (50 kg ha-1) and inoculums Bradyrhizobium (1.5 kg ha-1) in improving the yield of two mungbean varieties (BARI mung-5 and BARI mung-6). The experiment was carried out during the period from April 2011 to July 2011 at the Sher-e-Bangla Agricultural University (SAU) Farm, Dhaka. The experiment was laid out in Randomized Complete Block Design (RCBD) with four replications and plot size was 8 m2 with 30 cm line spacing. The Bradyrhizobium strain BARI RVr-403 was used for the experiment. The recommended dose of TSP, MOP and Gypsum were applied in each plot. BARI Mung-6 performed higher stover and seed yield than BARI Mung-5. Bradyrhizobium inoculation significantly increased 1000-seed weight, pods plant-1, seeds pod-1, stover and seed yield. BARI Mung-6 with Bradyrhizobium inoculation recorded the highest seed and stover yield compared to other treatment combinations. Non-inoculated BARI Mung-5 gave the lowest yield.

Efficient nitrogen (N) fertilizer management is critical for wheat production and the long-term protection of the environment. Given the importance of durum wheat for the Italian economy, its environmental implications need to be investigated for designing sustainable production system. Three concurrent experiments were carried out in Gravina in Puglia (Apulia, southern Italy) to investigate the agronomic and environmental response of rainfed durum wheat (Triticum turgidum L., var. durum) to different N rates, N source and application time over three years (2010e2012). In the three experiments, the following parameters were analyzed: grain yield, yield components (i.e. harvest index, spikes m À2), quality traits (i.e. hectoliter weight, protein content), energy input/output analysis including the calculation of energy indexes and greenhouse gas (GHG) emissions. The N rate experiment included rates of 45, 90 and 135 kg N ha À1. Each rate was split in various proportions between sowing, tillering and stem elongation. For the experiment on N timing and splitting, a single dose of 90 kg N ha À1 was split between sowing, tillering and stem elongation at different fractions (0-90-0; 40-50-0; 10-40-40). The N fertilizer source experiment tested the effect of the application of 90 kg N ha À1 of urea split at sowing and tillering (12-78-0) on the investigated parameters, and compared to Entec ® 26 and Sulfammo 23 with the same does and application time. Nitrogen agronomic efficiency (NAE) was also calculated to assess the potential yield increase in response to different N fertilizer rates and types. The results showed that N rate, N source and the application time had a significant impact on grain yield, grain protein content, energy output and GHG emissions under normal weather conditions. Considering the site-specific condition, the overall results revealed that the split application of 90 kg N ha À1 during three growth stages gave favorable results in terms of grain yield and quality, and optimizes NAE with less environmental impact. The effectiveness and efficiency of this strategy was more pronounced when two-third of the full N dose was applied at later stages (tillering and stem elongation). This strategy found to be more effective in improving wheat yield and quality than the increase in the N rate, which could offer the potential to decrease N fertilization rate in wheat production. This study provides useful information for farmers on how to manage the N fertilization of wheat for sustainable production system.

Aflatoxin accumulation in maize is strongly influenced by the environment in which the crop is grown. To gain insights into the ways in which soil fertility influences aflatoxin, we investigated the relationships between agronomic traits and aflatoxin in diverse maize testcrosses that were grown under two nitrogen treatment levels. The experiment was conducted in Eastern Kenya, an aflatoxin-endemic area, with natural Aspergillus flavus inoculum. A panel of 205 maize lines was grown under low soil nitrogen (N low = 26 kg/ha applied N) in the long season of 2011 and a subset of the genotypes (n = 123) was grown under high soil nitrogen (N high = 114 kg/ha applied N) in the short season of 2010 and long season of 2011. Kernel traits, grain yield, days to anthesis, ear rot, and aflatoxin were analyzed for the panel. Grain yield, protein, and kernel bulk density were higher in maize grown under N high compared to maize grown under N low , with grain yield twice as high under N high. A higher proportion of plots had grain with detectable aflatoxin under N low than under the N high. When the maize testcrosses were grouped into three maturity categories based on days to anthesis, aflatoxin accumulation was twice as high in the late-maturing group than in the other two categories under N low. The proportion of aflatoxin contamination was higher in dent than in flint maize. However, the extent of aflatoxin accumulation did not differ significantly (P > 0.05) over the entire testcross panel, among maize genotypes within the maturity groups or among kernel texture groups within the maturity groups. Kernel bulk density and protein content were higher in early and intermediate groups than in the late maturity group. Grain yield did not differ among the maturity groups (P > 0.05), but significant positive correlations were observed between the proportion of grain yield reduction due to low soil nitrogen stress and aflatoxin in early and late maturity groups. Kernel bulk density was negatively correlated with aflatoxin in grain. No significant association was observed between aflatoxin and ear rot or kernel size. We conclude that aflatoxin mitigation strategies should include soil nitrogen amendment and breeding approaches that include selection for the correlated agronomic traits.

Nitrogen fertilizer practices affect nitrous oxide (N2O) emissions from agricultural soils. The “4R” nutrient stewardship framework of using N fertilizer at the right rate, right source, right placement and right time can reduce N2O emissions while maintaining or improving yield of field crops, but understanding of how the various factors affect N2O emissions from irrigated processing potato is lacking. We examined the effects of selected 4R practices on emissions, using results from two irrigated processing potato studies each conducted in 2011 and 2012 in Manitoba, Canada. Experiment 1 examined combinations of source (urea, ESN), placement (pre-plant incorporation [PPI], banding), and rate (100 and 200 kg N ha-1) on a clay loam soil. Experiment 2 examined timing and source treatment combinations (urea PPI, ESN PPI, urea split, urea split/fertigation) on a loamy fine sandy soil. For Experiment 1, use of ESN at 200 kg ha-1 did not reduce area-, yield- and applied fertilizer N- based N2O emissions compared to urea at 200 kg ha-1, irrespective of placement. Emissions from pre-plant banding ESN at 200 kg ha−1, however, were 32% lower than from PPI ESN. For Experiment 2, compared to single pre-plant urea application, fertigation simulated by in-season application of urea ammonium nitrate (UAN) gave lower area-, yield- and applied fertilizer N- based emissions. Split urea (  2/32/3  pre-plant,  1/31/3  hilling) also reduced area- and yield- based N2O emissions compared to single pre-plant urea application. Emissions were generally lower at the site with loamy fine sandy soil than the site with clay loam soil. These results demonstrate that combinations of “4R” practices rather than source alone are best to achieve reductions in N2O emissions from irrigated potato production.

Porous soils are characterized by high infiltration, low moisture retention and poor fertility due to limitation of organic matter and nitrogen (N). However, wherever irrigated and properly managed, these are among the most productive soils in the world. For sustained productivity and prevention of N related pollution problems, fertilizer N management in porous soils needs to be improved by reducing losses of N via different mechanisms. Losses of N through ammonia volatilization are not favoured in porous soils provided fertilizer N is applied before an irrigation or rainfall event. Ammonium N transported to depth along with percolating water cannot move back to soil surface where it is prone to be lost as NH3. Under upland conditions nitrification proceeds rapidly in porous soils. Due to high water percolation rates in porous soils, continuous flooding for rice production usually cannot be maintained and alternate flood and drained conditions are created. Nitrification proceeds rapidly during drained conditions and nitrates thus produced are subsequently reduced to N2 and N20 through denitrification upon reflooding. Indirect N-budget estimates show that up to 50% of the applied N may be lost via nitrification-denitrification in irrigated porous soils under wetland rice.

Proper management practices such as plant spacing and nutrient management are the most effective means for increasing yield of rice. To date no single spacing or nutrient management has been recommended as ideal for all field conditions for a particular variety which must be established experimentally. The current experiment was, therefore, conducted to study the effect of integrated nitrogen management and plant spacing on the growth, yield and yield components of monsoon rice (rainfed transplanted rice) cv. BRRI dhan41. The experiment consisted of the following sets of treatments: factor (A) integrated nitrogen management: control, i.e., no urea super granule (USG), prilled urea (PU) and poultry manure (PM) (T1), 1.8 g USG 4 hill-1 (T2), 2.7 g USG 4 hill-1 (T3), PM at 5 t ha-1 (T4), PM at 7.5 t ha-1 (T5), 1.8 g USG 4 hill-1 + PM at 5 t ha-1 (T6), 2.7 g USG 4 hill-1 + PM at 7.5 t ha-1 (T7), 1.8 g USG 4 hill-1 + PM at 2.5 t ha-1 (T8), 2.7 g USG 4 hill-1 + PM at 3.75 t ha-1 (T9), recommended dose of PU i.e., 240 kg ha-1 (T10), 1/2PU + PM at 5 t ha-1 (T11), full dose of PU + PM at 7.5 t ha-1 (T12), 1/2PU + PM at 2.5 t ha-1 (T13) and full dose of PU + PM at 3.75 t ha-1 (T14); and factor (B) plant spacing: 25 cm × 15 cm (S1) and 25 cm × 20 cm (S2). The experiment was laid out in a randomized complete block design with three replications. Integrated nitrogen management showed significant effect on all the yield and yield contributing characters except number of non-effective tillers hill-1 , panicle length and weight of 1000 grains. The results revealed that the highest grain yield (3.67 t ha-1) was obtained from T6 and the lowest grain yield (1.39 t ha-1) was obtained from T1. All the yield and yield contributing characters were significantly affected by plant spacing except number of total tillers hill-1 , number of non-effective tillers hill-1 , panicle length and weight of 1000 grains. The spacing 25 cm × 20 cm resulted in higher grain yield (3.05 t ha-1) than the spacing 25 cm × 15 cm. Grain yield was affected by the interaction of integrated nitrogen management and plant spacing. The highest grain yield (3.74 t ha-1) was recorded with the interaction between T6 and S2 while the lowest one (1.36 t ha-1) was obtained from T1 and S1 combination. Therefore, for higher yield monsoon rice cv. BRRI dhan41 should be planted following 25 cm × 20 cm spacing and fertilized with 1.8 g USG 4 hill-1 + 5 t ha-1 PM to meet nitrogen requirement.

Ammonia synthesis is the most important step for nitrogen-fertilizer production and consumes approximately 1% of the world’s energy production and energy-related greenhouse gas emissions. In addition to the concomitant emissions caused by ammonia and nitrogen fertilizer synthesis, centrally produced fertilizer that must be distributed to farms also harms the environment because of the embodied energy of transportation. An environmentally-optimal nitrogen fertilizer system would be distributed on farms themselves using only renewable inputs. Recent developments in solar photovoltaic technology and subsystems for ammonia production have made non-organic on-site ammonia production physically possible. This study provides a technical evaluation of the process for on-site nitrogen-fertilization of corn using solar photovoltaic electricity as the energy input. The system consists of a water electrolysis system to generate hydrogen and a membrane system to generate nitrogen needed as material inputs. Total power consumption for syngas preparation to generate a unit of ammonia is calculated. System total energy consumption is calculated while compensating syngas preparation with heat recovery. Five case-study locations are evaluated to determine their suggested nitrogen fertilizer addition (N-rate) for corn growth and the energy consumption for suggested N-rate is calculated. The System Advisor Model (SAM) is then used to simulate the PV system output for those five locations. Finally, the PV land use required as a fraction of the corn field area is determined. The results indicate that because PV is so much more efficient at solar energy conversion than organic methods, even the worst case evaluated in Indiana requires less than 1% of the corn field converted to a PV system to provide enough energy to generate sufficient amounts of ammonia for fertilizer for the remaining corn. The system was modeled to provide ammonia to fertilize for corn fields larger than 1079 acres with the worst soil conditions, the area of which applies to more than half of cropland in the U.S. in 2011. As the finiteness and emissions of fossil fuel production of nitrogen become more important, this renewable system should become economical and future investigations into its overall viability are warranted.

Photosynthesis in C3 plants is significantly limited by mesophyll
conductance (gm), which can vary with leaf anatomical
traits and nitrogen (N) supplements. Several studies have
investigated the response of gm to N supplements; however,
none examined the implications of N supplements on the
response of gm to rapid environmental changes. Here we
investigated the effect of N supplement on gm and the
response of gm to change of CO2, temperature and irradiance
in rice. High N supplement (HN) increased mesophyll cell
wall surface area and chloroplast surface area exposed to
intercellular airspace per leaf area, and reduced cell wall
thickness. These changes resulted in increased gm. The gm of
leaves with HN was more sensitive to changes in CO2 concentration,
temperature and irradiance.The difference in leaf
structural features between low N supplement and HN indicates
that a rapid change in gm is related to the regulation of
diffusion through biological membranes rather than leaf
structural features. These results will contribute to an understanding of the determinants of gm response to rapid changes in environmental factors

BACKGROUND: With the increasing demand for high-quality foodstuffs and concern for environmental sustainability,
late-season nitrogen (N) foliar fertilization of common wheat is now an important and widespread practice. This study
investigated the effects of late-season foliar versus soil N fertilization on yield and protein content of four varieties of durum
wheat, Aureo, Ariosto, Biensur and Liberdur, in a three-year field trial in northern Italy.
RESULTS: Variations in low-molecular-weight glutenins (LMW-GS), high-molecular-weight glutenins (HMW-GS) and gliadins
were assessed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). It was found that N applied to the
canopy did not improve protein rate compared with N application to the soil (general mean 138mg g−1), but moderately
increased productivity in the high-yielding varieties Liberdur and Biensur (three-year means 7.23 vs 7.13 and 7.53 vs 7.09 t
ha−1 respectively). Technological quality was mainly related to variety choice, Aureo and Ariosto having higher protein rates
and glutenin/gliadin ratios. Also found was a strong ‘variety × N application method’ interaction in the proportions of protein
subunits within each class, particularly LMW-GS and gliadins. A promising result was the higher N uptake efficiency, although
as apparent balance, combined with higher HMW/LMW-GS ratio in var. Biensur.
CONCLUSION: Late-season foliar N fertilization allows N fertilizer saving, potentially providing environmental benefits in the
rainy climate of the northern Mediterranean area, and also leads to variety-dependent up-regulation of essential LMW-GS and
gliadins. Variety choice is a key factor in obtaining high technological quality, although it is currently associated with modest
grain yield. This study provides evidence of high quality in the specific high-yielding variety Biensur, suggesting its potential as
amono-varietal semolina for pasta production.

Chlorophyll meters are widely used to guide nitrogen (N) management by monitoring leaf N status
in agricultural systems, but the effects of environmental factors and leaf characteristics on leaf N
estimations are still unclear. In the present study, we estimated the relationships among SPAD
readings, chlorophyll content and leaf N content per leaf area for seven species grown in multiple
environments. There were similar relationships between SPAD readings and chlorophyll content per
leaf area for the species groups, but the relationship between chlorophyll content and leaf N content
per leaf area, and the relationship between SPAD readings and leaf N content per leaf area varied
widely among the species groups. A significant impact of light-dependent chloroplast movement on
SPAD readings was observed under low leaf N supplementation in both rice and soybean but not
under high N supplementation. Furthermore, the allocation of leaf N to chlorophyll was strongly
influenced by short-term changes in growth light. We demonstrate that the relationship between
SPAD readings and leaf N content per leaf area is profoundly affected by environmental factors and
leaf features of crop species, which should be accounted for when using a chlorophyll meter to guide
N management in agricultural systems.

Water and nitrogen (N) are two key limiting factors for citrus production. Reported effects of water and N inputs on citrus yield, water use efficiency (WUE) and N use efficiency (NUE) vary greatly, mainly due to differences in cultivars, tree age, climate, soil types, and water and N input levels. So far, no systematic analysis has been performed, and as a result, the interactive effects of water and N inputs on yield, WUE and NUE of citrus orchards are unknown. Also, gaps between attainable and actual yields, WUE and NUE have not been established yet. Here, we report on a global meta-analysis of yields, WUE and NUE of citrus production systems, using 1009 observations from 55 studies, conducted in 11 countries. Median citrus yields ranged from 30 to 60 t ha-1, which were in between average global yields (range 10-30 t ha-1) and attainable yields (range 60-90 t ha-1). Median WUE ranged from 2.5 to 5 kg m-3 and median NUE from 150 to 350 kg kg-1. Citrus yields were related to water and N inputs and tree age. Relationships between water and N inputs and yield, WUE and NUE were also analysed for sub-datasets and quantiles, to examine the relationships near the extremes. There were statistical significant interactions between water and N inputs in yield and NUE, but not in WUE. This indicates that studies aiming at the optimization of water and N inputs must consider interactions and optimize water and N inputs simultaneously. Based on our analyses, we estimated that reducing over-optimal irrigation to optimal irrigation may increase citrus yield by 20%, WUE by 30% and NUE by 15%. Similarly, reducing over-optimal N fertilization to optimal N fertilization may increase yield by 10%, WUE by 15% and NUE by 40%. We concluded that there is room for a significant increase in yield, WUE and NUE through the simultaneous optimization of water and fertilizer N inputs via precision fertigation

El maíz (Zea mays L.) es un cultivo tradicional ecuatoriano, constituye un componente importante en la dieta tanto de la población rural como urbana. El maíz, Zea mays L., es uno de los granos alimenticios más antiguos que se conocen. Pertenece a la familia de las Poáceas (Gramíneas), y es la única especie cultivada de este género. El maíz (Zea mays) constituye, junto con el arroz y el trigo, uno de los principales alimentos cultivados en el mundo y junto al fréjol forman parte principal de la alimentación tradicional que suministra cantidades significativas de nutrientes, sobre todo calorías y proteínas, por lo que es el componente básico de los sistemas de producción y alimentación.

Smoleń S., Sady W. 2005. Wpływ zróżnicowanego nawożenia azotem i dokarmiania dolistnego na akumulację Cd, Cu i Zn w marchwi. [W:] Obieg pierwiastków w przyrodzie. Monografia. Tom III. red. Gworek B. Instytut Ochrony Środowiska, Warszawa: 357-360 Wpływ zróżnicowanego nawożenia azotem i dokarmiania dolistnego na akumulację Cd, Cu i Zn w marchwi Effect of differentiated nitrogen fertilization and foliar application on Cd, Cu and Zn accumulation in carrot roots Sylwester Smoleń, Włodzimierz Sady

In a time of resource reduction and climate variability, water conservation is critical to improve agroecosystem sustainability. Non-ionic surfactants were recently hypothesized as irrigation adjuvants, but so far researchers obtained contrasting results. The first objective of this work was to evaluate the capillary adsorption properties of organosilicone surfactants by providing two robust tests on standard porous media. Results showed smaller capillary mobility and higher wetting power (" superspreading ") compared to pure water. An innovative non-ionic surfactant formulation, the organosilicone PET (PolyEther-modified Trisiloxane), was then investigated as irrigation adjuvant in a pot trial on lettuce in absence of fertilization. Overall, the system was characterized by an improvement in the processes of resource acquisition, i.e. water and nutrients. Results indicated higher lettuce leaf area, reduced root dry weight and root:shoot ratio and a positive main effect on the uptake, availability and/or use efficiency of P, K and some micronutrients. The N use efficiency and recovery increased 3–15%, with higher N concentration and content against changes in plant weight. Fresh yield data showed a particularly high irrigation use efficiency (+77–60%), and the adjuvant productivity (variation of lettuce yield due to PET) increased by 12–26%. Our experimental findings can be explained by hypothesizing that PET affected both capillary and adsorption processes during water diffusion along concentration gradients, which constitute the main driving force for solutes movement towards the roots. A theoretical model is provided to explain how PET improved the thickening and interconnection of conductive adsorbed water film in soil.

A field experiment was carried out during the autumn season of 2015 in Abu Gharaq area (10 km west of Hilla city) to study the effect of five supplemental nitrogen fertilizer treatments (as whole or split in two parts) and four genotypes of maize on yield and its components. Factorial experiment according to split plot arranged within randomized complete block design (RCBD) with three replications was used .Four genotypes of maize (US hybrid , Hispanic hybrid, Euphrates hybrid and popcorn) placed in sup-plot and the Main-plot included the addition of supplemental nitrogen fertilizer (urea 46% N) in five levels (0 , 100 kg N.ha-1 as whole or split in two parts and 200 kg N.ha-1 as whole or split in two parts). The genotypes were differ in most traits studied. Furat hybrid was superior in total grain yield and gave the highest rate of 8.74 t.ha-1 , biological yield (17.26 t.ha-1) , weight of 300 grain (141.9 g) , and the number of rows per ear (14.48). Popcorn was superior in plant ear number (1.73) and the number of grains per row (37.88). Nitrogen fertilizer levels differed in most traits studied. The addition of 100 kg N.ha-1 (split in two parts) was superior in weight of grain per ear (132.9 g), weight of 300 grain (121.1 g), and the addition of 200 kg N.ha-1 1 ‫الثاني‬ ‫للباحث‬ ‫ماجستير‬ ‫رسالة‬ ‫من‬ ‫جزء‬

The nitrogen (N) cycle is an important part of earth's biogeochemical cycles and N is a critical element for all life. Whereas the response to N-and more rarely phosphorus, P-fertilization of some microbial groups involved in soil N cycling has been studied, a comprehensive view of how the major microbial groups involved in soil N dynamics respond to combined N and P fertilization is lacking, which restricts our understanding of ecosystem responses to fertilization. Here we investigated the effects of different N, P and NP fertilizer levels (4 N levels without P; 4 P levels without N; and 4 P levels with constant N addition) on the abundances of 9 microbial groups involved in N dynamics. Real time PCR was used to target free N 2 fixers, nitrifiers (bacterial and archaea ammonia oxidizers, AOB and AOA, respectively; and the nitrite oxidizers Nitrobacter and Nitrospira), nitrate reducers, nirK-and nirS-nitrite reducers, and nitrous oxide reducers. Soil physical-chemical characteristics and potential nitrification, PNR, were also measured. N fertilization increased the abundances of AOB and Nitrobacter but did not affect the abundances of the other groups. P fertilization decreased the abundances of N 2 fixers, nitrate reducers and AOA, and increased the abundances of Nitrobacter and nitrous oxide reducers. NP fertilization decreased the abundances of AOA and nirK-nitrite reducers. Using a correlation network analysis, we demonstrate the strong coupling generally observed in these grasslands between N 2 fixers, AOA, Nitrospira, narG-nitrate reducers and nirK-denitrifiers (most of them responding to N/P availability, and being known to be favored by low oxygen availability); and between AOB and Nitrobacter (known to be favored by high oxygen and high N levels) that controlled changes in PNR. The observed (de)coupling between the responses of the different microbial groups may have major consequences for N cycling and N losses from fertilized Tibetan alpine meadows.

Our understanding of the response of vascular, terrestrial plants to nitrogen (N) addition is advanced and provides the foundation for modern agriculture. In comparison, information on responses of marine macroalgae to increased nitrogen is far less developed. We investigated how in situ pulses of nitrate (NO3 −) affected the growth and N physiology of Macrocystis pyrifera by adding N using potassium nitrate dissolution blocks during a period of low seawater N concentration. Multiple parameters (e.g. growth, pigments, soluble NO3 −) were measured in distinct tissues throughout entire fronds (apical meristem, stipe, adult blade, mature blade, sporophyll, and holdfast). Unexpectedly, N fertilisation did not enhance elongation rates within the frond, but instead thickness (biomass per unit area) increased in adult blades. Increased blade thickness may have enhanced tissue integrity as fertilised kelp had lower rates of blade erosion. Tissue chemistry also responded to enrichment; pigmentation, soluble NO3 −, and % N were higher throughout fertilised fronds. Labelled 15N traced N uptake and translocation from N sources in the kelp canopy to sinks in the holdfast, 10 m below. This is the first evidence of long-distance (>1 m) transport of N in macroalgae. Patterns in physiological parameters suggest that M. pyrifera displays functional differentiation between canopy and basal tissues that may aid in nutrient-tolerance strategies, similar to those seen in higher plants and unlike those seen in more simple algae (i.e. non-kelps). This study highlights how little we know about N additions and N-use strategies within kelp compared to the wealth of literature available for higher plants.

Biofortification of vegetables with iodine can become an alternative method to salt iodization of introducing this element to human diet. Iodine is not an essential nutrient for plants and its effect on plant growth and development has not yet been sufficiently examined. The aim of the study was to assess the influence of soil fertilization with iodine (in the form of Iand IO 3 -) and nitrogen (applied as NO 3 and NH 4 + ) on the effectiveness of iodine biofortification as well as mineral composition of carrot storage roots. Carrot cv. Kazan F 1 was cultivated in a field experiment in 2008 and 2009. Different soil fertilization treatments with iodine as well as nitrogen were tested, including: 1 -control without N

Use of inorganic fertilizers constitutes 20% of the rice production cost in Mwea. Azolla fern, which grows in Mwea Irrigation paddies, has the potential to supplement the nitrogen requirement, thus reducing the fertilizer costs. A field experiment was conducted in Mwea Irrigation Scheme during 2015 long and short rains to determine the effect of Azolla incorporation and inorganic nitrogen on growth and yield of rice. The treatments comprised three nitrogen fertilizer levels (0, 30 and 60kg N ha-1) and three Azolla biomass levels (0, 7.5 and 15tons ha-1) laid out in a randomized complete block design with a split-plot arrangement. Data on plant height and number of tillers per plant were collected at 21, 35, 45, and 65 and 75 days after transplanting rice while yield and yield components were determined at 120 days after transplanting rice. Soil was analysed for N, P and K, before and after termination of the experiment. Data were subjected to analysis of variance using SAS and means...

The influence of different ground cover management systems on the development of the vine mealybug, Planococcus ficus Signoret (Hemiptera: Pseudococcidae), was evaluated in a commercial vineyard (cv. Carignano) in north-western Sardinia within an ongoing multi-year project. In this paper, preliminary results of the first year of observations are reported. The field trial was arranged in a randomized block design, comparing traditional tillage and three different cover crops: natural self-regenerating (legume-grass mixture), grass (Dactylis glomerata L.) and legume (Trifolium yanninicum Katzn. & Morley). In each treatment, some life parameters of the vine mealybug (survival, development time from egg to ovipositing female and fecundity) and the nitrogen content of grapevines, measured by a SPAD meter, were recorded. The ground cover management systems affected the vegetative growth of grapevines. In fact, the SPAD values were significantly higher on tillage and legume cover crop, whi...

Investigation about effect of high amounts of nitrogen and source of nutrition on winter triticale productivity was carried out in a stationary field trial in the Sumadija region, in Central Serbia. This study was conducted over a period of three years (2009-2011) on a vertisol soil to evaluate the effect of different fertilization methods on grain yield and yield components of winter triticale variety. Treatments included control and six fertilization variants with different combinations of NPK fertilizers (N, NK, NP1, NP2, NP1K, and NP2K). Investigation showed a considerable variation of grain yield depending on mineral nutrition. The highest and statistically significant average grain yields were achieved under NP1K (4.105 t ha-1) and NP2K (4.050 t ha-1) treatments. The combined use of NP1K fertilizers (120 kg N ha-1 , 60 kg P2O5 ha-1 , 60 kg K2O ha-1) and NP2K treatment (120 kg N ha-1 , 100 kg P2O5 ha-1 , 60 kg K2O ha-1) represented the excellent base for optimum stock of major nutrients, resulting in maximum grain yield. Thousand grain weight of triticale significantly varied across years, the highest average 1000-grain weight of winter triticale investigated was achieved in the NP1K variant (44.81 g). Grain yield was significantly positively correlated with 1000-grain weight only in all years.

The widespread use of nitrogen (N) fertilizers during the second half of the 20 th century radically transformed agricultural production and ecosystems on a global scale. Although the "N challenge" or the "N problem" has had limited public attention compared to biodiversity loss and climate change, scientists consider N pollution a leading ecological concern for the 21 st century. Accordingly, a major challenge for scientists and policymakers around the world today is how to meet food production demands while also protecting the environment. Using Chile as a case study—one of the highest consumers of N fertilizer per hectare in the Americas—this article examines the transnational politics of production and destruction in this process of agricultural modernization. In the Cold War context, a transnational network of scientists, agencies, and authorities created an institutional framework for the transference of knowledge and technology in Chile during the 1960s. Paradoxically, as local and global reliance on N fertilizers increased, scientists were able to generate a narrative about the negative environmental effects of intensive N use and highlight the ecological limits of the Green Revolution. After 1973, however, this knowledge network suffered as a result of the Chilean government's anti-communist crackdown and adoption of market-based agricultural policies. Understanding this history of how politics shaped N consumption, science, and policy is critical to current efforts to create new of agricultural production on a regional and global scale.

L'utilisation généralisée des engrais azotés (N) durant la seconde moitié du XXe siècle a transformé radicalement la production agricole et les écosystèmes à l'échelle mondiale. Les scientifiques considèrent la pollution N comme une préoccupation écologique majeure pour le 21ème siècle. Mais le "défi N" ou le "problème N" a eu une attention limitée du public par rapport à la perte de biodiversité et au changement climatique,. En conséquence, un défi majeur pour les scientifiques et les décideurs du monde entier aujourd'hui est de répondre aux demandes de production alimentaire tout en protégeant l'environnement. En utilisant le Chili comme étude de cas-l'un des plus grands consommateurs d'engrais N par hectare dans les Amériques-cet article examine la politique transnationale de production et de destruction dans ce processus de modernisation agricole. Dans le contexte de la Guerre froide, un réseau transnational de scientifiques, d'agences et de autorités a créé un cadre institutionnel pour le transfert de connaissances et de technologie au Chili au cours des années 1960. Paradoxalement, à mesure que la dépendance locale et mondiale sur les engrais N augmentait, les scientifiques pouvaient générer un récit sur les effets environnementaux négatifs de l'utilisation intensive de N et mettre en évidence les limites écologiques de la «Révolution verte». Après 1973, cependant, ce réseau de connaissances a souffert de la répression anticommuniste du gouvernement chilien et de l'adoption de politiques agricoles basées sur le marché. La compréhension de cette histoire de la façon dont la politique est axée sur la consommation, la science et la politique de N est essentielle-pour les efforts actuels visant à créer une nouvelle production agricole à l'échelle régionale et mondiale.

El extendido uso de fertilizantes de nitrógeno (N) durante la segunda mitad del siglo XX, transformó radicalmente de manera global la producción de la agricultura y los ecosistemas. A pesar de que el "Reto N" o el "Problema N" ha tenido una atención limitada en comparación con temas como la pérdida de la biodiversidad y el cambio climático, científicos consideran que contaminación N, es una preocupación primordial para el siglo XXI. Por tanto, satisfacer las demandas de producción de alimentos a la par de la protección del ambiente, es actualmente un reto para científicos y quienes hacen políticas públicas alrededor del mundo. A partir del caso de Chile-uno de los mayores consumidores de fertilizante N por hectárea en América-este artículo examina las políticas transnacionales de producción y destrucción en el proceso de modernización de la agricultura. En el contexto de la Guerra Fría, una red transnacional de científicos, agencias y autoridades, crearon en la década de 1960 en Chile, un marco institucional para la transferencia de conocimiento y tecnología. Paradójicamente, a medida que la dependencia a los fertilizantes N aumento local y globalmente, científicos fueron capaces de generar una narrativa acerca del intensivo uso de N y sus efectos negativos en el medio ambiente, y así marcar los límites ecológicos de la Revolución Verde. Sin embargo, después de 1973, esta red de conocimiento se vio afectada como resultado de las medidas anticomunistas y la adopción de políticas de agricultura basadas en el mercado, por parte del gobierno Chileno. Para los actuales esfuerzos de crear una nueva producción agrícola a escalas regional y global, resulta crítico el tener un entendimiento de la historia de cómo las políticas dieron forma al consumo, la ciencia y las políticas de nitrógeno.

Resumo -O objetivo deste trabalho foi avaliar a resposta de genótipos de milho (Zea mays L.), cultivado em sistema de plantio direto, a diferentes quantidades de palha de aveia-preta (Avena strigosa Schreb.) e doses de nitrogênio. O experimento foi conduzido em um Latossolo Vermelho eutrófi co, em delineamento experimental de blocos ao acaso em parcelas subsubdivididas, com três repetições. As parcelas principais foram representadas pelas quantidades de palha na superfície do solo (sem palha, 5,16 e 10,32 Mg ha -1 ). As subparcelas foram representadas por três genótipos de milho e as subsubparcelas constituíram-se das doses 0, 60, 120, 180 e 240 kg ha -1 de nitrogênio. O aumento da dose de nitrogênio reduziu a requeima das folhas e promoveu o suprimento adequado de nitrogênio das plantas de milho em todos os tratamentos com palha de aveia-preta. Os genótipos de milho diferenciaram-se quanto à produtividade de grãos, ao aproveitamento do nitrogênio mineralizado da palha e ao comprimento do sistema radicular, quando submetidos a diferentes quantidades de palha de aveia-preta e de nitrogênio.

Nitrogen isotopic studies have the potential to shed light on the structure of ancient ecosystems, agropastoral regimes, and human-environment interactions. Until relatively recently, however, little attention was paid to the complexities of nitrogen transformations in ancient plant-soil systems and their potential impact on plant and animal tissue nitrogen isotopic compositions. This paper discusses the importance of understanding nitrogen dynamics in ancient contexts, and highlights several key areas of archaeology where a more detailed understanding of these processes may enable us to answer some fundamental questions. This paper explores two larger themes that are prominent in archaeological studies using stable nitrogen isotope analysis: (1) agricultural practices (use of animal fertilizers, burning of vegetation or shifting cultivation, and tillage) and (2) animal domestication and husbandry (grazing intensity/stocking rate and the foddering of domestic animals with cultigens). The paucity of plant material in ancient deposits necessitates that these issues are addressed primarily through the isotopic analysis of skeletal material rather than the plants themselves, but the interpretation of these data hinges on a thorough understanding of the underlying biogeochemical processes in plant-soil systems. Building on studies conducted in modern ecosystems and under controlled conditions, these processes are reviewed, and their relevance discussed for ancient contexts.

1. Nitrogen (N) and phosphorus (P) often limit biological processes in terrestrial ecosystems. Based on previous studies mainly focusing on plants, the concept of resource limitation has evolved towards a theory of (co)limitations by multiple resources. However, this ecological framework has not been applied to analyse how soil microorganisms and plants concurrently respond to N and/or P addition, and whether these responses are constrained by phylogenetic relatedness.
2. Here, we applied this framework to analyse microbial and plant responses at community and taxon levels to different fertilization treatments (four N levels without P; four P levels without N and four NP levels) in Tibetan grasslands.
3. Total plant biomass showed serial limitation by N then P, and most plant species were limited by N only. Total archaeal abundance decreased with P addition, but diverse nutrient limitation types were observed for archaeal taxa. Closely related archaeal taxa tended to similarly respond to N, and functional similarity between distant archaeal groups was observed for response to P, possibly due to functional convergence. In contrast, total bacteria slightly increased with P addition only when plants remained N limited, whereas without N limitation, plants rather than bacteria benefited from P addition. Most bacterial taxa were limited by other resources than N and P, and no clear phylogenetic signals were observed regarding bacterial responses to N/P additions.
4. Synthesis. We propose a novel approach for characterizing microbial response types to nutrient addition. It demonstrates that in Tibetan meadows, most dominant plant species, archaea and bacteria, respectively, depend on N, both N and P and other resources.

Nitrogen deficiency influences importantly the plant photosynthetic capacity and crop productivity. Here, we employed the rapid, non-invasive measurements of chlorophyll a fluorescence kinetics for calculation of the integrative fluorescence parameters related to the leaf photosynthetic performance. In pot experiments with winter wheat (Triticum aestivum L.) we cultivated plants during the whole growing period in the soil substrate supplied with four different doses of nitrogen. The leaf nitrogen and chlorophyll content as well as the plant dry mass were analyzed after chlorophyll fluorescence records in three growth stages. Our results indicate that the commonly used parameter Fv/Fm (the maximum quantum yield of photochemistry) was almost insensitive to nitrogen treatment. In contrary, the performance index (PIabs) and total performance index (PItot) were much more responsive and significant differences among plants of different nitrogen treatments as well as between the youngest and third leaf from the top were observed. Parameter PItot was shown to express only small diurnal changes, thus being more reliable and more useful for comparison of different samples in field conditions than more frequently used parameter PIabs.

Plant nitrogen isotopic compositions are highly variable and are influenced by a diversity of environmental and anthropogenic factors, including the application of animal-derived fertilizers. Legumes that acquire most of their nitrogen from atmospheric N2 (rather than mineralized soil nitrogen) tend to have relatively low δ15N values (consistently around 0 ‰), and it has been presumed that their δ15N values are largely or wholly unaffected by fertilization. This study presents nitrogen isotopic data from leguminous (garden bean, Phaseolus vulgaris) and non-leguminous (summer squash, Cucurbita pepo) plants subjected to seabird guano fertilization while growing under controlled conditions. Both bean and squash tissue δ15N values were substantially increased by seabird guano fertilization: +16.3 to +19.2 ‰ for bean and +19.6 to +24.5 ‰ for squash. The results of this study demonstrate that the enrichment in plant 15N resulting from seabird guano fertilization occurs consistently in non-maize species. Moreover, it demonstrates that under conditions of high soil nitrogen availability, leguminous plants may obtain a substantial portion of their nitrogen through the uptake of inorganic soil nitrogen (ammonium and nitrate), rather than atmospheric N2. In general, where the δ15N values of fertilizers differ substantially from that of endogenous soil nitrogen and mineralized nitrogen derived from the fertilizer is readily available, a significant manuring effect can be expected in leguminous plants.

Two field experiments were carried out at the Agriculture Research Station, Qassim University, during the period 2003-2004, to study the effects of irrigation frequencies and N fertilization rates on date palm offshoots growth. A drip irrigation system was used to irrigate the experiments. The soil texture of the experimental site was loamy sand. The first experiment consisted of four irrigation intervals: daily; every three days; every four days and every five days (hereafter referred to as 1-day, 3-day, 4-day, and 5-day, respectively). All irrigation treatments received 500 g of nitrogen for each tree. The urea fertilizer was used as a source of nitrogen. The second experiment consisted of three rates of nitrogen in the form of urea. These rates were 500, 750, and 1000 g N/tree, respectively (hereafter referred to as urea-1, urea-2, and urea-3, respectively). All urea treatments were irrigated daily. The survival percentages for each experiment were recorded. In addition, the number of leaves, new offshoots, fresh and dry weights of seven pinnae, length ratio (final length/initial length) of offshoots, and the chlorophyll level were measured. The survival percentages for the irrigation and fertilization experiments were 87.5 and 86.7 %, respectively. The chlorophyll levels were 60.4, 58.4, 57.5 and 54.0 mg/m 2 for the irrigation treatments 1-day, 3-day, 4-day, and 5-day, respectively. It is obvious that the chlorophyll level decreased as the irrigation intervals had increased. The irrigation levels of 3-day and 4-day gave high new offshoots number, number of leaves and length ratio. However, the differences among the irrigation treatment means were not significant at 5% level. The chlorophyll levels were 59.0, 59.6, and 54.1 mg/m 2 for the N-fertilization rates urea-1, urea-2, and urea-3, respectively. It is obvious that the chlorophyll level decreased with the increase of Nitrogen rates applied. The urea-2 treatment has the greatest number of leaves in comparison to the other urea treatments.

This study investigated the effects of a commercial biofertilizer containing the mycorrhizal fungus Rhizophagus irregularis and the diazotrophic N-fixing bacterium Azotobacter vinelandii on root and shoot growth, yield, and nutrient uptake in common wheat (Triticum aestivum L.) in order to improve the sustainable cultivation of this widespread crop. The trials were carried out in controlled conditions (rhizoboxes) and in open fields over two years to investigate the interaction between inoculation and three doses of nitrogen fertilization (160, 120 and 80 kg ha −1) in a silty-loam soil of the Po Plain (NE Italy). In rhizoboxes, efficient root colonization by R. irregularis was observed at 50 days after sowing with seed inoculation, together with improved root tip density and branching (+~30% vs. controls), while the effects of post-emergence inoculation by soil and foliar spraying were not observable at plant sampling. In the open, field spraying at end tillering significantly increased the volumetric root length density (RLD, +22% vs. controls) and root area density (+18%) after about two months (flowering stage) in both years under medium and high N fertilization doses, but not at the lowest N dose. In absence of inoculation, RLD progressively decreased with increased N doses. Inoculation had a negligible effect on grain yield and N uptake, which followed a typical N dose-response model, while straw Zn, P, and K concentrations were seldom improved. It is concluded that medium-high N fertilization doses are required to achieve the target yield and standards of quality (protein contents) in wheat cultivation, while the use of this mixed VAM-PGPR biofertilizer appears to be a sustainable mean for minimizing the adverse effects of chemical N fertilizers on root expansion and for improving the uptake of low-mobility nutrients, which has potentially relevant environmental benefits.

Nitrogen is one of the most limiting elements in almost all soils. Thus, proper application of nitrogen fertilizers is vital to improve crop growth and grain yields. Insufficient and/or inappropriate nitrogen fertilizer management is highly damaging to the crops. Optimal nitrogen management strategies aim at matching the nitrogen fertilizer supply to the actual crop demand. The Leaf Color Chart (LCC) is a tool for real time, or need based nitrogen management in rice. LCC based nitrogen management without its basal application assisted to save significant amount of nitrogen (30 to 37.5 Kg N ha-1) in case of inbred varieties (Radha-4 and Sukkha-5) as compared to recommended practice with 120 Kg N ha-1 applied in three equal splits. On the other hand, the requirement of nitrogen for hybrid US-312 was remarkably higher than that of inbred varieties. However, pure LCC based nitrogen management significantly decreased the amount of excess nitrogen application as compared to the all other LCC based treatments. All the nitrogen management treatments including LCC were similar to each other in respect of grain yield formation (4695 – 4891 Kgha-1), but significantly superior over recommended practice (4408 Kg ha-1). The hybrid rice US-312 was significantly more productive (4695 Kgha-1) than inbred varieties, i.e Radha-4 (4089 Kgha-1) and Sukkha-5 (4315 Kgha-1) which differed insignificantly. Thus, pure LCC based nitrogen management was the most economic practice for both inbred and hybrid varieties of rice.

Film mulching is a very common technique in agriculture worldwide, but few studies have focused on the dry matter (DM) and N accumulation of mulched crops. Understanding the grain yield (GY) associated with DM and N accumulation is essential for improving crop production. We conducted a 3-yr field experiment with six N fertilizer rates (0, 100, 200, 250, 300, and 400 kg ha -1 ) in the semiarid climate of northwest China to determine the GY and DM and N accumulation of film-mulched maize (Zea mays L.). The results showed that relatively high GYs (13.1-15.1 Mg ha -1 ) were obtained using N fertilizer rates of 200 to 400 kg ha -1 in the 3 yr despite large year-to-year differences in rainfall. When the N rate was below 250 kg ha -1 , the GY, DM, and N accumulation increased significantly as the N fertilizer rate increased. A linear-plateau model best described the relationship between the GY and the DM and N accumulation during the pre-silking stage and a linear model the relationship during the post-silking stage. We conclude that optimizing N management to improve DM and N accumulation (especially postsilking) is the key to ensuring a high yield of film-mulched maize.

Improvement in use efficiency of N fertilizers can potentially better sustain agriculture by reducing N 2 O emissions from soils, but little is known about its impact on soil CO 2 emissions. A study, involving both a field experiment and a laboratory incubation, was conducted in eastern Canada to determine the N fertilization effect on soil CO 2 emissions. In laboratory, we incubated nine different types of soil with and without 150 kg N ha −1 as KNO 3 or (NH 4) 2 SO 4. The N-fertilized soils had lower CO 2 emissions compared with the no-N control soils for six of them. Among fertilizer sources, emissions of CO 2 were on average 22% lower with KNO 3 than with (NH 4) 2 SO 4. The field experiment conducted on a clay soil included three sources of N (urea-NH 4 NO 3 , CaNH 4 NO 3 , and aqua NH 3) at 0–200 kg N ha −1 band-incorporated at the six-leaf corn stage. Under field conditions, most CO 2 was emitted between N application and grain maturity with cumulative seasonal soil emissions greater in the control (4.9 Mg C ha −1) than in the N treatments (average of 4.0 ± 0.3 Mg C ha −1). Evidence suggested that both hetero-trophic and autotrophic respiration seemed affected, whereas the NO 3-based source had a more depressing effect on CO 2 emissions than did the NH 4 source. Résumé : Rehausser l'efficacité des engrais azotés pourrait profiter à l'agriculture par une réduction du N 2 O libéré du sol, mais on sait peu de choses au sujet des répercussions d'une telle bonification sur les émissions de CO 2. Les auteurs ont réalisé une étude dans l'est du Canada incluant une expérience sur le terrain et une incubation en labo-ratoire en vue de préciser les conséquences de l'usage de tels engrais sur les dégagements de CO 2 par le sol. Au labo-ratoire, ils ont incubé neuf types de sol avec et sans addition de 150 kg N ha −1 sous forme de KNO 3 ou de (NH 4) 2 SO 4. Les sols amendés avec l'engrais N libéraient moins de CO 2 que les sols témoins non bonifiés, dans six cas. Quand on compare les engrais, on constate que les émissions de CO 2 sont en moyenne 22 % plus faibles avec le KNO 3 qu'avec le (NH 4) 2 SO 4. L'expérience réalisée sur le terrain consistait en l'incorporation en bande de 0 à 200 kg de N ha −1 de trois sources de N (urée-NH 4 NO 3 , CaNH 4 NO 3 et NH 3 liquide) à un sol argileux, au stade six feuilles du maïs. Dans les conditions ambiantes, la majeure partie du CO 2 a été émise entre l'application du N et la maturation du grain, les émissions saisonnières cumulatives étant plus grandes pour la parcelle témoin (4,9 Mg C ha −1) que pour les parcelles amendées (moyenne de 4,0 ± 0,3 Mg C ha −1). Ces résultats suggèrent que les amendements affectent à la fois la respiration hétérotrophe et autotrophe, et que les engrais à base de NO 3 réduisent plus les émissions de CO 2 que les engrais à base de NH4. [Traduit par la Rédaction] Mots-clés : engrais N-ammonium, émissions de dioxyde de carbone, maïs, engrais N-nitrate, respiration du sol.

In soils, nitrogen (N) addition typically enhances ammonia oxidation (AO) rates and increases the population density of ammonia-oxidizing bacteria (AOB), but not that of ammonia-oxidizing archaea (AOA). We asked if long-term inorganic N addition also has similar consequences in arid land soils, an understudied yet spatially ubiquitous ecosystem type. Using Sonoran Desert top soils from between and under shrubs within a long-term N-enrichment experiment, we determined community concentration-response kinetics of AO and measured the total and relative abundance of AOA and AOB based on amoA gene abundance. As expected, N addition increased maximum AO rates and the abundance of bacterial amoA genes compared to the controls. Surprisingly, N addition also increased the abundance of archaeal amoA genes. We did not detect any major effects of N addition on ammonia-oxidizing community composition. The ammonia-oxidizing communities in these desert soils were dominated by AOA as expected (78% of amoA gene copies were related to Nitrososphaera), but contained unusually high contributions of Nitrosomonas (18%) and unusually low numbers of Nitrosospira (2%). This study highlights unique traits of ammonia oxidizers in arid lands, which should be considered globally in predictions of AO responses to changes in N availability.