Papers by D. Kumaragamage
Canadian Journal of Soil Science, 2007
Quantitative relationships between soil test phosphorus (STP) methods are needed to guide P manag... more Quantitative relationships between soil test phosphorus (STP) methods are needed to guide P management especially in manured soils with high P. Our objectives were: (i) to compare amounts of P extracted by different methods; (ii) to develop and verify regression equations to convert results among methods; and (iii) to establish environmental P thresholds for different methods, in manured and non-manured soils of Manitoba. We analyzed 214 surface soil samples (0–15 cm), of which 51 had previous manure application. Agronomic STP methods were Olsen (O-P), Mehlich-3 (M3-P), Kelowna-1 (original; K1-P), Kelowna-2 (modified; K2-P), Kelowna-3 (modified; K3-P), Bray-1 (B1-P) and Miller and Axley (MA-P), while environmental STP methods were water extractable (W-P), Ca Cl2 extractable (Ca-P) and iron oxide impregnated filter paper (FeO-P) methods. The different methods extracted different amounts of P, but were linearly correlated. For an O-P range of 0–30 mg kg-1, relationships between O-P an...
Canadian Journal of Soil Science, 2019
Metal-contaminated soils present a great threat to natural ecosystems and human health. Remediati... more Metal-contaminated soils present a great threat to natural ecosystems and human health. Remediation studies focusing on metal-polluted soils with high organic matter (OM > 20%) are limited. This study evaluated the effectiveness of biochar, compost, diammonium phosphate (DAP), and iron oxides (Fe-O), in immobilizing metals from an OM-rich boreal forest soil contaminated with arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn). A laboratory incubation study was conducted with soil amended with biochar (5% w w−1), compost (5% w w−1), DAP (0.2% w w−1), or Fe-O (0.2% w w−1), and a control (without amendment) for 6 months at field capacity moisture content. Metal concentrations were determined in pore water collected at 0, 2, 4, and 6 months after incubation. Soil was extracted sequentially for metals after the incubation period. Metal concentrations in pore water were significantly reduced by different amendments as follows: As by biochar and Fe-O, Cd by biochar, compos...
The Journal of Agricultural Science, 2019
Amendment of recalcitrant organic materials with high carbon/nitrogen (C/N)-ratio may improve and... more Amendment of recalcitrant organic materials with high carbon/nitrogen (C/N)-ratio may improve and maintain soil labile C for a longer period, thus enhancing the productivity of soils with low fertility; however, immobilization of N may affect the plant growth negatively. To reduce the negative impacts, recalcitrant organic materials can be pre-incubated with N-rich sources or applied in combination with fertilizers. The current study evaluated sawdust biochar (BC) and pre-incubated cattle manure–sawdust mixture (CS) amendments with synthetic fertilizers in improving soil carbon pool, soil fertility and maize (Zea mays L.) yield on a tropical Alfisol. Four treatments: control, site-specific fertilizer (SSF), site-specific fertilizer with sawdust biochar (BC + SSF) or pre-incubated cattle manure-sawdust mixture (CS + SSF), were evaluated for two seasons with maize. The residual effect was evaluated in the third season. During the year of active C application, lability index, C managem...
Current Pollution Reports, 2018
Manure is a valuable source of plant nutrients; however, continuous application to soils may lead... more Manure is a valuable source of plant nutrients; however, continuous application to soils may lead to accumulation of phosphorus (P), increasing the risk of P loss into waterways triggering freshwater eutrophication. This review paper summarizes and critically evaluates relevant research findings published within the last 5 years on manure P mobility in soils and management strategies to mitigate losses identifying future research needs. Past and recent research evidence on manure P mobilization and losses from soils have yielded inconsistent and often confounding results, because of the interactive effects of source factors and the existence of concurrent transport pathways. Although far from being conclusive, a few general trends are worth noting; P losses were greater with (a) increasing soluble P applied with manure, (b) vulnerable soils with limited P sorption capacity and/or susceptible to preferential flow/erosion, (c) conditions conducive to P release and transport, and (d) reduced soil-manure P interaction following application. Effective mitigating strategies included (a) generating low-P manure, (b) processing manure to reduce total and/or soluble P, and (c) adopting best management practices (BMPs) during and post-manure application. Future research should focus on a better understanding of the interactive effects of source factors on short- and long-term manure P loss via different transport pathways. Existing mitigation efforts and new directions should focus on reducing P buildup in soil by employing a combination of strategies during generation, processing, and application of manure, coupled with site- and time-specific BMPs selected based on the dominant pathway of P loss.
Journal of Environment Quality, 2016
. Variation of dissolved reactive phosphorus (DRP) concentration (mg L -1 ) in pore water during ... more . Variation of dissolved reactive phosphorus (DRP) concentration (mg L -1 ) in pore water during the flooding period from surface and subsurface soils (geometric means). † Mean values followed by the same lowercase letter within a row are not significantly different. ‡ Mean values followed by the same uppercase letter within a soil and sampling date for the two soil depths are not significantly different.
Tropical Agricultural Research, 2016
Beneficial management practices can be used to improve the crop productivity of tropical Alfisols... more Beneficial management practices can be used to improve the crop productivity of tropical Alfisols. This study evaluated beneficial management practices to overcome the soil physical and chemical limitations for growing maize (Zea mays). The experiment was conducted in the Low Country Dry Zone (DL1b) on Reddish Brown Earth soil (Typic Rhodustalf). Four treatments; un-amended control (C), site specific fertilizer (SSF), biochar applied at 1 t/ha with SFF (BC+SSF) and rock powder applied at 10 t/ha with SSF (RP+SSF) were tested using maize as the test crop initially in the greenhouse and later in the field at DL1b for two growing seasons (2013 Yala and 2013/2014 Maha) for their effects on crop growth and soil fertility. Soil was neutral, non-saline, sandy clay loam in texture with comparatively high clay content (27%) and low in organic matter content (1.5%) and deficient in N, P, S, Ca, Zn, and Cu, initially. In the greenhouse, plant dry weight increased significantly with the addition of amendments i.e., fertilizers alone (SSF), or BC+SSF or RP+SSF. In the field study, no significant differences were observed for soil pH with the addition of amendments but biochar application significantly increased cation exchange capacity, organic matter, potentially mineralizable nitrogen and carbon management index. Rock powder+SSF and BC+SSF significantly increased the grain yield over the control in both seasons. Both labile and recalcitrant C were significantly higher in BC+SSF treatment than the others. Further, application of BC and RP had no significant impact on soil textural fractions and bulk density, yet in both seasons, BC+SSF application increased the aggregate stability greater than other treatments. The results of the field experiment suggest that biochar and rock powder with adequate nutrients effectively improved soil fertility and productivity.
Journal of Environment Quality, 2019
Prolonged flooding changes the oxidation-reduction status of soils, often enhancing P release to ... more Prolonged flooding changes the oxidation-reduction status of soils, often enhancing P release to overlying floodwater. We studied P release from unamended, gypsum-amended, and biochar-amended soils under simulated snowmelt flooding (previously frozen, cold flooding at +4°C) and summer flooding (unfrozen, warm flooding at +22°C) using two soils, Fyala clay (FYL-Cl) and Neuenberg sandy loam (NBG-SL), from Manitoba, Canada. Amended and unamended soils were packed into vessels and flooded under cold and warm temperatures in the laboratory. Pore water and floodwater samples were taken weekly for 6 wk after flooding (WAF) and thereafter biweekly for 10 WAF and analyzed for dissolved reactive P (DRP), pH, and cation concentrations. The NBG-SL showed a significantly higher DRP concentration in pore water and floodwater despite its low Olsen P content. Redox potential (Eh) decreased slowly under cold versus warm flooding; hence, redox-induced P release was substantially lower under cold flooding. Gypsum amendment significantly decreased the floodwater DRP concentrations in NBG-SL by 38 and 35% under cold and warm flooding, respectively, but had no significant effect in FYL-Cl, which had low DRP concentrations (<1.2 mg L −1) throughout the flooding period. Biochar amendment significantly increased floodwater DRP concentrations by 27 to 68% in FYL-Cl under cold and warm flooding, respectively, but had no significant effect in NBG-SL. The results indicate substantially less P release under cold than under warm flooding. Gypsum was effective in reducing floodwater DRP concentrations only at high DRP concentrations; thus, the effectiveness was greater under warm than under cold flooding conditions.
Proceedings of International Forestry and Environment Symposium, Feb 20, 2014
1) and five replicates for a single experiment. Soil samples were taken at 4, 8, 10, 12 and 16 we... more 1) and five replicates for a single experiment. Soil samples were taken at 4, 8, 10, 12 and 16 weeks after planting (WAP). The soil samples were analysed for soil pH, electrical conductivity (EC) and available Phosphorus (Olsen's method). The leaf Phosphorus content at 50% tasseling stage was measured using dry ash method. The growth parameters were plant heights at 4, 8, 10 and 12 WAP, number of days to 50% tasseling and number of days to 80% silking. Results indicate soil pH, EC, and leaf Phosphorus % are not significantly different (p<0.05) at different levels of Phosphorus in both locations. However, soil available Phosphorus is significantly different (p<0.05) to the control. Conversely it does not show significant different (p<0.05) among fertilized treatments at both sites. Moreover, plant height at 50% tasseling stage, number of days to 50% tasseling and number of days to 80% silking are not significantly different (p<0.05) among any treatments at both soil types. Hence, the results further revealed that the different levels of P treatments have no significant effect on soil pH, EC, available P, leaf P and growth parameters of maize variety Sampath under greenhouse conditions.
Tropical agricultural research, 2009
A balanced nutrient application was used to measure the yield, quality and post harvest life of c... more A balanced nutrient application was used to measure the yield, quality and post harvest life of cauliflower. Soils collected from two experimental sites at Dodangolla and Pelwehera were analysed for available nutrients and a balanced nutrient treatment was formulated. Field experiments were conducted for 4 consecutive seasons comparing the balanced nutrient treatment with other treatments including the Department of Agriculture (DOA) recommendation, and different combination of N, P, K, secondary and micronutrients using a Randomized Complete Block Design. Soil analysis indicated deficient levels of N, P, K in both locations, and Ca, S, B, Mn, only at Dodangolla. Cultural practices and crop protection were done according to the recommendations of the DOA. During the vegetative stage, plant height at one week after transplanting and 50% flowering, number of leaves at 50% flowering, Leaf Area Index at 50% flowering, number of days to flowering, time period for curd maturity were measu...
Use of multi nutrient extractants to assess available nutrients in soils is economically advantag... more Use of multi nutrient extractants to assess available nutrients in soils is economically advantageous in routine soil testing. Even though AB-DTPA extractant has been proved to be successful for alkaline soils, its potential as a multi nutrient extractantfor acidic soils has not been documented. This study examined the suitability of AB-DTPA extractant to determine plant available P, K, Na, Ca, Mg, Fe, Mn, Cu and Zn in acidic and neutral soils of Sri Lanka. Thirty one soils were collected from different locations, including alfisols, ultisols, entisols, and inceptisols. Available nutrient status of soils was analyzed by conventional methods as well as by AB-DTPA method. Conventional methods tested were; Olsen and Bray-1 methods for available P, neutral ammonium acetate extraction for exchangeable Ca, Na, K and Mg, and DTP A extraction for available Fe, Mn, Cu and Zn.
Kg Bulgugsa Plutonic Rocks Amnokgang Comp., Bulgugsa Granite Jg Jgl Daebo Plutonic Rocks Daebo Gr... more Kg Bulgugsa Plutonic Rocks Amnokgang Comp., Bulgugsa Granite Jg Jgl Daebo Plutonic Rocks Daebo Granite, Tanchon Comp. Foliated Granite Tg Songrim Plutonic Rocks Hyesan Comp., Pyonggang Comp. PAg Paleozoic Igneous Activity Namgang Comp., Chongjin Comp., Tumangang Comp. PRg ARg Archean-Proterozoic Igneous Activity Buncheon Granite, Hongjesa Granite, Sancheong Anortho site, Riwon Comp., Sakju Comp., Pyoksong Comp., Ongjin Comp., Seosan Granite Gneiss, Yonsan Comp. Rangrim Granite, Andol Comp., Ryonhwasan Comp. Superimposed Sedimentary Cover Q3 Q2 Q1 N P Cenozoic Sedimentary Basin Marine Sediments Basalt, Trachyte, Volcanic Rocks Basalt, Trachyte Hamgyong Gp., Yeonil Gp. Anju Gp., Janggi Gp. Mesozoic Sedimentary Basin K3 K2
The average production of bitter gourd (Momordica charantia L.) in Sri Lanka had remained stagnan... more The average production of bitter gourd (Momordica charantia L.) in Sri Lanka had remained stagnant during the last decade despite the introduction of high yielding varieties. Farmers in general, use blanket fertilizer recommendations supplying only N, P, and K for bitter gourd. This study was conducted to evaluate the site specific approach in fertilizer recommendation for bitter gourd grown in a Reddish Brown Earth soil (Rhodustalfs) at CIC farm, Pelvehera, Sri Lanka. The systematic approach tested involved soil sampling, chemical analysis, nutrient sorption studies, greenhouse and field experiments. Soil analysis indicated deficient levels of N, P, K, Cu and Mo of 14, 28, 122, 3.6 and 1.4 mg/kg of soil, respectively. The nutrient levels for an optimum fertilizer treatment were formulated based on the results of routine analysis and a sorption study. Result from the greenhouse experiment indicated that out of the deficient nutrients, only addition of the N, P and K significantly in...
Inadequate and unbalanced supply of mineral nutrients may be one reason for the lower yields of v... more Inadequate and unbalanced supply of mineral nutrients may be one reason for the lower yields of vegetables in Sri Lanka. Site-specific fertilizer management is a modern approach that could increase the fertilizer use efficiency with minimum environmental impacts. This research was conducted to evaluate the potential of using a systematic approach of diagnosing soil nutrient problems in improving the present fertilizer recommendation for cauliflower. Soils collected from the two experimental sites at Dodangolla and Pelwehera, Sri Lanka were analysed for available nutrients using a three- step extraction method. Nutrient contents were compared with the established optimum values to identify deficiencies. Fixation studies conducted for P, K, Cu, Zn, Fe, Mn, S and B were used to adjust the amount of fertilizer to be supplemented. An optimum fertilizer recommendation formulated for each soil was tested in the greenhouse using a modified missing element technique using sorghum (Sorghum vu...
Intensified agriculture associated with higher use of fertilizer and irrigation water has resulte... more Intensified agriculture associated with higher use of fertilizer and irrigation water has resulted in significant contamination of aquifer particularly in soils with shallow water table and high permeability. Proper management of fertilizer and irrigation could be one of the best ways to attend this problem. A leaching experiment was conducted in the laboratory with soil columns to characterize nitrate movement in sandy Regosols. Soil columns were prepared at 20, 30 and 40 cm depths with sieved sandy Regosols to a bulk density of 1.6 gcm -3 and saturated with distilled water. Each column was fertilized at the rate of 0, 70 and 140 kg N/ha. Water was applied at the rates of 7, 14 and 30 mm with each fertilization in each column. Leachate was collected and nitrate concentration was measured. Breakthrough Curves obtained in all runs have shown that NO3 - concentration increased, reached to a peak and then reduced to zero. The peak nitrate flux and the attenuation varied with irrigation...
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Papers by D. Kumaragamage