Soil Organic Carbon Composition in a Northern Mixed‐Grass Prairie

Agriculture, Ecosystems & Environment, 2013

Conversion of native prairie land for agricultural production has resulted in significant loss and redistribution of soil organic matter (SOM) in the soil profile ultimately leading to declining soil fertility in a low-productivity semiarid agroecosystem. Improved understanding of such losses can lead to development of sustainable land management practices that maintain soil fertility and enhance soil quality. This study was conducted to determine whether conservation practices impact soil profile carbon (C) and nitrogen (N) accumulation in central High Plains. Soil samples were taken at four-depth increments to 1.2 m in July of 2011 from five unfertilized fields under long-term management with varying degrees of soil disturbance: (1) historic wheat (Triticum aestivum)-fallow (HT)-managed with tillage alone, (2) conventional wheat-fallow (CT)-input of herbicides for weed control and fewer tillage operation than historic wheat-fallow, (3) no-till wheat-fallow (NT)-not plowed since 2000 and herbicides used for weed control, (4) grass-legume mixture-established in 2005 as in the Conservation Reserve Program (CRP), and (5) native mixed grass prairie (NP)-representing a relatively undisturbed reference location. Cumulative soil organic C (SOC) was not significantly different among the three wheat-fallow systems when the whole profile (0-120 cm) was analyzed. However, SOC, dissolved organic C (DOC), and total soil N contents decreased in the direction NP > CRP ≥ NT > HT ≥ CT in the surface 0-30 cm depth. In the surface 0-30 cm depth, estimated annual SOC storage rate averaged 0.28 Mg C ha −1 year −1 since the cessation of tillage in 2000 and 0.58 Mg C ha −1 year −1 since the establishment of CRP grass-legume mixture in 2005. Cumulative soil inorganic C (SIC) accumulation ranged between 8.1 and 24.9 Mg ha −1 and was greatest under wheat-fallow systems, particularly at deeper soil layers, relative to the perennial systems (NP and CRP). Results from this study suggest that repeated soil disturbance induced by cropping and fallow favored large accumulation of SIC which presence may result in decline in soil fertility and productivity; whereas conversion from tilled wheat-fallow to CRP grass-legume mixture offers great SOC storage potential relative to NT wheat-fallow practices.

Managing Agricultural Greenhouse Gases, 2012

Inadequate soil management is one of the primary causes of pasture degradation, aggravated by the replacement of natural forest environments with cultivated pastures. Thus, the objective of the present study was to quantify the flux of CO 2 and organic carbon of the soil in grasslands undergoing intensive and extensive management, and in a native forest. The experiment was conducted in a randomized block design, with three treatments: intensive management system (IMS), extensive management system (EMS), and native vegetation (NV). The collected soil variables consisted of CO 2 flux, organic carbon, temperature, and humidity. The CO 2 flux quantification was obtained using LI-COR 8100-A equipment, chamber model 103. Carbon

Science of The Total Environment, 2020

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High Mountain Conservation in a Changing World, 2017

Mountain grasslands are generally rich in soil organic C, but the typical high spatial variability of mountain environments, together with the different management systems, makes their soil C content particularly variable. Socioeconomic changes of the past decades have caused a progressive abandonment of the traditional use for grazing of some areas, while grazing pressure at easily accessible grasslands have increased. Here, we analyse the effect of these land-use changes on the factors regulating the soil C accumulation and stocks. Overgrazing generally leads to a reduction above-and below-ground litter inputs and a decrease in soil C stocks, affecting some soil physicochemical and biological properties. Additionally, the labile C inputs coming from animal faeces may accelerate the mineralisation of organic matter. Grazing abandonment causes a reduction of aboveground productivity, but the lack of consumption causes a short-term accumulation of organic matter. Its effect on belowground biomass and productivity is less clear. At longer term, grazing abandonment causes a change in the plant community composition, having the shrub encroachment the strongest effect on C storage. The low biochemical quality of shrub litter delays its decomposition and allows higher organic matter accumulation in the topsoil. But the effect of shrub proliferation at the deeper soil is less clear. The low root turnover of shrubs compared to grasses may reduce the C inputs to the soil. But, at the same time, the reduction of the root exudates may also reduce the microbial activity and the organic matter mineralisation.

Geoderma, 2014

Tillage in dryland winter wheat (Triticum aestivum L.)-summer fallow cropping systems of the central High Plains, USA, has caused significant erosion and loss of soil organic matter (SOM), underscoring the need for more sustainable practices on marginally-productive semiarid lands. Conversion to no-till (NT) wheat-fallow or perennial grass-legume cover, as in the Conservation Reserve Program (CRP), provides viable alternatives to tillage-based wheat-fallow practices. However, the overall impact of transitioning on soil biogeochemistry is not fully understood. Labile SOM pools were determined on soil cores (0-120 cm) collected in July 2011 from five unfertilized fields that spanned a gradient in disturbance associated with land-use practices: a more intensively tilled wheat-fallow ('historic', HT) than a conventional (CT) wheat-fallow with limited herbicides combined with tillage, NT wheat-fallow that exclusively used herbicides for ≥ 10 years, formerly cultivated HT wheat-fallow planted to grass-legume mixture as in the CRP for 7 years, and native prairie (NP) with no history of agricultural disturbance. Significant differences in microbial biomass C (MBC), potentially mineralizable C (PMC) and nitrogen (PMN) were largely confined to the surface soil (0-30 cm), following the order NP N CRP N all wheat-fallow systems. When expressed on a per soil organic C (SOC) basis, both MBC and PMC followed the order CRP N NP N all wheat-fallow systems. In contrast, when normalized by total soil N (TN), PMN was higher in HT and CT soils than in other soils (NT, CRP, and NP). MBC and PMC were positively correlated with SOC whereas PMN, soil pH, and electrical conductivity (EC) showed a negative relationship with SOC. These results suggest more efficient conservation of SOM under perennial grass-legume system than NT wheat-fallow rotation. We suggest that cessation of tillage alone may not be sufficient for the recovery of labile-pool SOM degraded through long-term cultivation in the absence of inputs for soil fertility renewal.

Netherlands Journal of Agricultural Science

In the period 1985-1990 field trials with N fertilization, grazing and mowing were conducted on a sandy soil and a loamy soil to investigate the accumulation of organic N and C in intensi vely managed grassland systems. Annual fertilizer rates of N varied from 250 to 700 kg ha-1 under grazing and from 0 to 700 kg ha-1 under mowing. On the grazed plots no significant ac cumulation of soil organic N occurred in the sandy oil, whereas in the loamy soil an average N accumulation of 245 kg ha-1 yr" 1 was found. The accumulation in the loamy soil was probably caused by the marine history of the soil and the fact that the soil was recently plowed and resown. The accumulation was independent of the level of fertilizer N applied, indicating that increased biomass production does not necessarily increase the return of dead organic mate rial to the soil. These results confirm the suggestion that the surplus of fertilizer N is largely lost to the environment. About four years after the start of the experiment the amounts of soil N and C were considerably higher under grazing than under mowing. In spite of the higher amount of soil N under grazing compared to mowing, approximately 71 % and 57 % of the extra amount of N returned to the soil by grazing is lost to the environment on the sandy and the loamy soil, respectively. The C/N ratio of the soil organic matter was lower in plots with fertilizer N application than in plots without fertilizer N. This difference was prob ably caused by a difference in C/N ratio of dead grass and roots that were returned to the soil.

Soil Science Society of America Journal, 2006

Plant species, and their interactions with the environment, determine both the quantity and chemistry of organic matter inputs to soils. Indeed, countless studies have linked the quality of organic matter inputs to litter decomposition rates. However, few studies have examined how variation in the quantity and chemistry of plant inputs, caused by either interspecific differences or changing environmental conditions, influences the dynamics of soil organic matter. We studied the effects of 16 grassland species from 4 functional groups (C3 and C4 grasses, forbs, and legumes) growing under ambient and elevated CO 2 (560 ppm) and N inputs (4 g m 22 yr 21) on soil carbon (C) and nitrogen (N) dynamics after 4 yr in a grassland monoculture experiment in Minnesota, USA. Specifically, we related soil C and N dynamics to variation among species and their responses to the CO 2 and N treatments in plant biomass and chemistry of roots, the dominant detrital input in the system. The 16 species caused much larger variation in plant litter inputs and chemistry, as well as soil C and N dynamics, than the CO 2 and N treatment. Not surprising, variation in the quantity of plant inputs to soils contributed to up to a twofold variation in microbial biomass and amount of respired nonlabile soil C. Root N concentration (across species and CO 2 and N treatments) was significantly negatively related to decomposition of nonlabile soil C and positively related to net N mineralization. Greater labile C inputs decreased rates of net N mineralization, likely because of greater N immobilization. Thus, of the traits examined, plant productivity, tissue N concentration, and labile C production such as from rhizodeposition were most important in causing variation in soil C and N dynamics among species and in response to altered atmospheric CO 2 and N supply.

2002

We sought to establish soil carbon contents at the field level in the Chariton Valley with this study. Four land uses were of special interest: switchgrass fields, row cropped fields, woodlots, and pastures. The study was broken into two projects with one project focused primarily on switchgrass and the other on pastures. Field methods entailed transect sampling of 224 soil pedons from 23 fields. Our data show soil organic carbon (SOC) content to range from 5.4 to 26.8 kg m-2 m and the overall mean and standard deviation being 11.8±3.9 kg m2 m. We found SOC content varies in a systematic manner across landscapes with maximum contents nearly consistently being found in toeslopes and minimum contents being found in backslopes. SOC content is also generally proportionally distributed in pedons with the top 0.2 m containing about 1⁄2 of the SOC found to a 1 m depth and the top 0.5 m containing about 3⁄4 of the SOC found to 1 m depth. SOC content varies with land use with pastures genera...

CO2 Sequestration [Working Title]

Understanding management-induced C sequestration potential in soils under agriculture, forestry, and other land use systems and their quantification to offset increasing greenhouse gases are of global concern. This chapter reviews management-induced changes in C storage in soils of grazing grassland systems, their impacts on ecosystem functions, and their adaptability and needs of protection across socioeconomic and cultural settings. In general, improved management of grassland/pasture such as manuring/slurry application, liming and rotational grazing, and low to medium livestock units could sequester C more than under high intensity grazing conditions. Converting cultivated land to pasture, restoration of degraded land, and maximizing pasture phases in mixed-cropping, pasture with mixed-livestock, integrated forestry-pasturage of livestock (silvopastoral) and crop-forestry-pasturage of livestock (agro-silvopastoral) systems could also maintain and enhance soil organic C density (SOCρ). In areas receiving low precipitation and having high erodibility, grazing exclusion might restore degraded grasslands and increase SOCρ. Yet, optimizing C sequestration rates, sowing of more productive grass varieties, judicial inorganic and organic fertilization, rotational grazing, and other climate-resilient approaches could improve overall farm productivity and profitability and attain sustainability in livestock farming systems.

Soil and Water Research, 2016

Burzyńska I. (2016): Losses of soluble forms of organic carbon in relation to different agro-technical treatment of meadows. Soil & Water Res., 11: 228−234. Studies were performed to determine the loss of soluble forms of organic carbon in differently used meadows on mineral soil. In a long-term experiment two variants were distinguished: a productive meadow (N120-AN and N120-CN) and a non-productive one (Kp-AN, Kp-CN, Kz-AN, Kz-CN). Productive meadows were fertilized with 120 kg N/ha/year, 34.9 kg P/ha/year, and 149.4 kg K/ha/year and mown three times a year. Nitrogen fertilization was applied in a form of ammonium nitrate (AN) and calcium nitrate (CN). The only agro-technical measure applied to non-productive meadows was the regular cutting of vegetation and leaving it on the plots (variants: Kp-AN and Kp-CN) or taking it away from the plots (variants: Kz-AN, Kz-CN). Significant positive Pearson's linear correlations were found between pH (in CaCl 2) of mineral soil and total organic carbon (TOC) content in the following variants: Kz-AN (r = 0.457**), N120-AN (r = 0.491**), and N120-CN (r = 0.424**) and in all meadows fertilized with AN (r = 0.243**). The obtained linear correlation coefficients between pH and TOC indicate that soil organic carbon may be lost as a result of progressive acidification of the soil. Dissolved organic carbon in the mineral meadow soil increased in the following order: Kp-CN > N120-CN > Kz-CN > N120-AN > Kp-AN > Kz-AN.

Geoderma, 2011

Better understanding of soluble carbon (C) dynamics in managed grasslands fertilised with animal manures is required to effectively estimate nutrient transport potential and C loss during land-use change. Two adjacent grassland plots, one amended with 100 m 3 ha − 1 of liquid swine manure annually since 1978 and another unamended for the same period, were either killed by glyphosate in the autumn or left with vegetation intact. Those killed were either (i) left as an undisturbed chemical fallow, (ii) ploughed (20 cm depth) by full inversion tillage (FIT) in the autumn, or (iii) ploughed (20 cm depth) in the following spring. Microbial biomass C (MBC) and soluble C fractions: hot-water extractable organic C (HWEOC), cold-water extractable organic C (CWEOC), and dissolved organic C from tension lysimeters (DOC) were monitored during one full year following herbicide application and ploughing. On both unmanured and manured sites, HWEOC was positively correlated with MBC. However, on the manured grassland the slope of the HWEOC:MBC relationship was 55% higher than on the unmanured site indicating that the manured grassland accumulated more potentially soluble C per unit MBC than the unmanured grassland. Compared to the plots with intact vegetation and the chemical fallow, full inversion tillage reduced HWEOC and CWEOC by 10 to 30%, on both manured and unmanured soils, and reduced DOC in the soil solution of the manured soils. Peak DOC concentrations measured in the field occurred when soils were water-logged, particularly on the manured grassland. Our results suggest that manured grasslands on poorly-drained soils accumulate important quantities of readily soluble C which are prone to export as DOC when the soil becomes water-saturated. However, full inversion tillage of these grassland soils attenuated the amounts of readily soluble C and, in particular, the peaks in DOC.

Soil Science Society of America Journal, 2008

Good management of rangelands promotes C sequestration and reduces the likelihood of these ecosystems becoming net sources of CO 2 . As part of an ongoing study, soil was sampled in 2003 to investigate the long-term effects of different livestock grazing treatments on soil organic carbon (SOC), total nitrogen (TN), and microbial communities. The three treatments studied (no grazing, EX; continuously, lightly grazed [10% utilization], CL; and continuously, heavily grazed [50% utilization], CH) have been imposed on a northern mixed-grass prairie near Cheyenne, WY, for 21 yr. In the 10 yr since treatments were last sampled in 1993, the study area has been subject to several years of drought. In the 0 to 60 cm depth there was little change in SOC in the EX or CL treatments between 1993 and 2003, whereas there was a 30% loss of SOC in the CH treatment. This loss is attributed to plant community changes (from a cool-season [C 3 ] to a warm-season [C 4 ] plant dominated community) resulting in organic C accumulating nearer the soil surface, making it more vulnerable to loss. Soil TN increased in the EX and CL treatments between 1993 and 2003, but declined in the CH treatment. Differences in plant community composition and subsequent changes in SOC and TN may have contributed to microbial biomass, respiration, and N-mineralization rates generally being greatest in CL and least in the CH treatment. Although no signifi cant differences were observed in any specifi c microbial group based on concentrations of phospholipid fatty acid (PLFA) biomarkers, multivariate analysis of PLFA data revealed that microbial community structure differed among treatments. The CH grazing rate during a drought period altered plant community and microbial composition which subsequently impacted biogeochemical C and N cycles.

Journal of Rangeland Science, 2011

A bstract. Converting the native rangelands to simplified agro nomic communities causes some changes in soil carbon, nitrogen and phosphorus. Establishing of perennial plant communities on formerly cultivated rangelands is expected to stabilize soil properties and increase the amount of C, N, P stored in rangeland soils, but there is little information on what plant communities are the most effective for improvement of soil C, N, P reserves. The purpose of this study was to compare soil C, N, and P pools in ungrazed native rangelands with plant community of Festuca-Centurea with those ungrazed pastures established by sowing non-native perennial grasses ( Agropyron elongatum and Agropyron desertorum), shrubs (Kochia prostrata), and wheat cultivation in continuous dry land farming system. Study site was located in Sisab Research Station in North Khorasan Province, Iran. The results showed that the total C, N and P contents in the soils under modified plant communities were less than t...

European Journal of Soil Science, 1997

Comparisons were made between the phenolic and carbohydrate signatures of soil profiles developed under grass, spruce and ash stands. Samples were collected from a brown earth soil which was originally under the same land use, but over the past 43 years has supported different monocultures. Distinct signatures associated with each litter type were recorded in individual profiles. A relatively undecomposed phenolic fraction from lignin and hydrolysable carbohydrate fraction from plants had accumulated in the soils under spruce and ash. This largely reflected the quantity and quality of the litter inputs from the spruce and ash compared with the grass. The phenolic and hydrolysable carbohydrate fractions accounted for as much as 60% of the total organic carbon concentration in the deep horizons. In the grassland profile both fractions were more decomposed than under ash and spruce suggesting that the forest profiles had rapidly accumulated a carbon pool with a comparatively slow rate of decomposition. This was most apparent from the spruce profile (which contained 398 mg g-' C carbohydrate hydrolysed using trifluoracetic acid (TFA) in the C horizon compared with 165 and 45 mg g-' C under ash and grass respectively). We conclude that the decay rate of these fractions is a function of the vegetation type.

Soil Biology and Biochemistry, 1994

The effects of soil texture and grassland management, i.e. rate of fertilizer N input, mowing vs grazing, and the number of years the site is under grass, on the amounts of soil organic C and N and on the rates of C and N mineralization were investigated. A positive relationship was found between the amount of organic N in the soil and the clay + silt content. The relationship was affected by the groundwater table. There was a negative relationship between the percentage of soil N mineralizing during incubation and the clay + silt content of the soil. The amount of organic C was only positively correlated with soil texture in the soils with a high water table, but the relationship was less clear. Except for the groundwater table, differences in the C-toN ratio of the soil organic matter in sandy soils confused the relationship of soil organic C with soil texture. Organic matter in podzol soils had C-toN ratios between 15 and 20 while in other sandy soils the C-toN ratio ranged from 10 to 18; in loams and clays the C-toN ratio was ca 10. The percentage of soil C mineralizing in sandy soils was negatively correlated with the C-toN ratio of the soil organic matter. The sandy soils with a C-toN ratio > 16 that were used for incubation contained black humus including small charcoal particles; both other sandy soils with a lower C-toN ratio contained brown humus without visible charcoal particles. So we hypothesize that sandy soils with a high C-toN ratio contained more inert C than sandy soils with a lo& C-toN ratio. The rate of N fertilization had no effect on soil organic C and N nor on the rates of C and N mineralization. Differences between the effects of grazing and mowing on soil organic C and N and the rate of C and N mineralization were very small and not very consistent. Both the amounts of soil organic C and N found and the rates of C and N mineralization were significantly higher in old grassland (10 yr) than in young grassland (l-3 yr). The increases in the mineralization rates were larger than the increases in soil organic C and N.. , availability of nitrogen in soils under leys. In Proceedings of the First General Meeting of the European Grassland Federation (P. F. J. Van Burg and G. H. Arnold, Eds), pp. 3945. Pudoc, Wageningen. Wolf J. and Janssen L. H. M. (1991) Effects of changing land use in the Netherlands on net carbon fixation.