Winter cover crops have been shown to reduce nitrate-N (NO3-N) losses in runoff water and are recommended by the Illinois Nutrient Loss Reduction Strategy (NLRS) for reducing nutrient losses from agricultural fields. ...Winter cover crops have been shown to reduce nitrate-N (NO3-N) losses in runoff water and are recommended by the Illinois Nutrient Loss Reduction Strategy (NLRS) for reducing nutrient losses from agricultural fields. With an estimated 80 percent of the NO3-N load in Illinois coming from agriculture, the NLRS stresses the importance of farmers’ voluntary implementation of best management strategies in order to reach these goals. This study compares the difference in NO3-N losses from tile drainage water from an annual ryegrass (AR, Lolium multiflorum) winter cover-cropped treatment to a conventional tillage (CT) control (fall chisel and spring field cultivation). Throughout the maize (Zea mays L.) growing season, tile drainage water was collected and analyzed for NO3-N concentrations. Despite the AR treatment having a 29% lower mean daily NO3-N concentration, there was no significant difference in total daily NO3-N flux between AR and CT for this study period of April-July 2015. The cumulative losses of NO3-N were calculated at 11.65 and 10.56 kg ha?1 NO3-N for the CT and AR treatment, respectively, or a 9.4% reduction in the AR treatment during the period of study. When the season was divided based on growing season periods, the NO3-N flux values were less for the cover crop while the AR was actively growing, greater for the cover crop for the period following annual ryegrass termination through maximum crop canopy, and lower for the cover crop in the late stages of vegetative growth through relative maturity.展开更多
A long-term （1982-2001） field experiment was conducted in a calcareous soil under wheat （Triticum aestivum L.）-wheat （Triticum aestivum L.）-maize （Zea mays L.） rotation system at Zhangye, Gansu Province, China...A long-term （1982-2001） field experiment was conducted in a calcareous soil under wheat （Triticum aestivum L.）-wheat （Triticum aestivum L.）-maize （Zea mays L.） rotation system at Zhangye, Gansu Province, China to determine the effects of long-term fertilization on crop yield, nutrients interactions, content and accumulation of nitrate-N in soil profiles. Twenty- four plots in a split-plot factorial with a combination of eight treatments （from nitrogen （N）, phosphorus （P）, potassium （K） and farmyard manure （M） applications） and 3 replications were selected. Main treatments were M and without M, and the sub-treatments were no-fertilizer （CK）, N, NP and NPK. When P and K fertilizers were part of treatments, their ratio to N was 1N：0.22P：0.42K. All M, P and K fertilizers were applied as the basal dressing. The grain yield was harvested each experimental period and straw yield for the period from 1988 to 1997. After crop harvest in 2000, the soil was sampled from the 0-20, 20-60, 60-100, 100-140 and 140-180 cm depths to determine NO3^--N content. Maize yield of CK in 2000 was only 28.2% of that in 1984, and wheat in 2001 was 25.7% of that observed in 1982. Average impact of fertilizers on grain yield decreased in the order of N 〉 M 〉 P 〉 K. Yield response to N and P fertilizers increased with progress of the experiment. The impact of K fertilizer showed no increase in grain yield during the initial 6 years （1982-1987）, moderate increase in the next 5 years （1988-1992）, and considerable increase in the last 9 years （1993-2001）. The straw yield trend was similar to grain yield. Accumulation and distribution of NO3^--N in soil was significantly affected by annual fertilizations. Mineral fertilizers （NP and NPK） led to NO3^- -N accumulation in most subsoil layers, with major impact in the 20-140 cm depth. The combination of mineral fertilizers and farmyard manure （MNP and MNPK） reduced soil NO3^--N accumulation in comparison to mineral fertilizers, It can be argued that long-term fertilization significantly enhanced grain and straw yield in this rotation scheme. The findings of this research suggest that it is important to balance application of mineral fertilizers and farmyard manure in order to protect soil and underground water from potential NO3^--N pollution while sustaining high productivity in the oasis agro-ecosystem.展开更多
Soil microbial activity is recognized as an important factor affecting nitrogen (N) release from slow-release fertilizers. However,studies on the effect of size and activity of soil microflora on fertilizer degradatio...Soil microbial activity is recognized as an important factor affecting nitrogen (N) release from slow-release fertilizers. However,studies on the effect of size and activity of soil microflora on fertilizer degradation have provided contrasting results. To date, no clear relationships exist between soil microbial activity and the release of N from slow-release fertilizers. Hence, the aim of this study was to better understand such relationships by determining the release of N from three slow-release fertilizers in soils with different microbial activities. Soils were amended with urea-formaldehyde (UF), isobutylidene diurea (IBDU), and crotonylidene diurea (CDU). Urea, a soluble fertilizer, was used as the control. Fertilized soil samples were placed in a leaching system, and the release of N was determined by measuring ammonium-N and nitrate-N concentrations in leachates during 90 d of incubation. Non-linear regression was used to fit N leaching rate to a first-order model. In all the treated soils, N was released in the order: urea (89%–100%) > IBDU (59%–94%) >UF (46%–73%) > CDU (44%–56%). At the end of incubation, N released from CDU did not differ (P > 0.05) among soils. On the contrary, UF and IBDU released significantly lower (P < 0.05) amounts of N in the soil with higher microbial activity and lower pH.The rate constant (K_0) for UF was lower (P < 0.05) in the soil with lower pH. Taken together, our results indicated that soil microbial size and microbial activity had a marginal effect on fertilizer mineralization.展开更多
文摘Winter cover crops have been shown to reduce nitrate-N (NO3-N) losses in runoff water and are recommended by the Illinois Nutrient Loss Reduction Strategy (NLRS) for reducing nutrient losses from agricultural fields. With an estimated 80 percent of the NO3-N load in Illinois coming from agriculture, the NLRS stresses the importance of farmers’ voluntary implementation of best management strategies in order to reach these goals. This study compares the difference in NO3-N losses from tile drainage water from an annual ryegrass (AR, Lolium multiflorum) winter cover-cropped treatment to a conventional tillage (CT) control (fall chisel and spring field cultivation). Throughout the maize (Zea mays L.) growing season, tile drainage water was collected and analyzed for NO3-N concentrations. Despite the AR treatment having a 29% lower mean daily NO3-N concentration, there was no significant difference in total daily NO3-N flux between AR and CT for this study period of April-July 2015. The cumulative losses of NO3-N were calculated at 11.65 and 10.56 kg ha?1 NO3-N for the CT and AR treatment, respectively, or a 9.4% reduction in the AR treatment during the period of study. When the season was divided based on growing season periods, the NO3-N flux values were less for the cover crop while the AR was actively growing, greater for the cover crop for the period following annual ryegrass termination through maximum crop canopy, and lower for the cover crop in the late stages of vegetative growth through relative maturity.
文摘A long-term （1982-2001） field experiment was conducted in a calcareous soil under wheat （Triticum aestivum L.）-wheat （Triticum aestivum L.）-maize （Zea mays L.） rotation system at Zhangye, Gansu Province, China to determine the effects of long-term fertilization on crop yield, nutrients interactions, content and accumulation of nitrate-N in soil profiles. Twenty- four plots in a split-plot factorial with a combination of eight treatments （from nitrogen （N）, phosphorus （P）, potassium （K） and farmyard manure （M） applications） and 3 replications were selected. Main treatments were M and without M, and the sub-treatments were no-fertilizer （CK）, N, NP and NPK. When P and K fertilizers were part of treatments, their ratio to N was 1N：0.22P：0.42K. All M, P and K fertilizers were applied as the basal dressing. The grain yield was harvested each experimental period and straw yield for the period from 1988 to 1997. After crop harvest in 2000, the soil was sampled from the 0-20, 20-60, 60-100, 100-140 and 140-180 cm depths to determine NO3^--N content. Maize yield of CK in 2000 was only 28.2% of that in 1984, and wheat in 2001 was 25.7% of that observed in 1982. Average impact of fertilizers on grain yield decreased in the order of N 〉 M 〉 P 〉 K. Yield response to N and P fertilizers increased with progress of the experiment. The impact of K fertilizer showed no increase in grain yield during the initial 6 years （1982-1987）, moderate increase in the next 5 years （1988-1992）, and considerable increase in the last 9 years （1993-2001）. The straw yield trend was similar to grain yield. Accumulation and distribution of NO3^--N in soil was significantly affected by annual fertilizations. Mineral fertilizers （NP and NPK） led to NO3^- -N accumulation in most subsoil layers, with major impact in the 20-140 cm depth. The combination of mineral fertilizers and farmyard manure （MNP and MNPK） reduced soil NO3^--N accumulation in comparison to mineral fertilizers, It can be argued that long-term fertilization significantly enhanced grain and straw yield in this rotation scheme. The findings of this research suggest that it is important to balance application of mineral fertilizers and farmyard manure in order to protect soil and underground water from potential NO3^--N pollution while sustaining high productivity in the oasis agro-ecosystem.
文摘Soil microbial activity is recognized as an important factor affecting nitrogen (N) release from slow-release fertilizers. However,studies on the effect of size and activity of soil microflora on fertilizer degradation have provided contrasting results. To date, no clear relationships exist between soil microbial activity and the release of N from slow-release fertilizers. Hence, the aim of this study was to better understand such relationships by determining the release of N from three slow-release fertilizers in soils with different microbial activities. Soils were amended with urea-formaldehyde (UF), isobutylidene diurea (IBDU), and crotonylidene diurea (CDU). Urea, a soluble fertilizer, was used as the control. Fertilized soil samples were placed in a leaching system, and the release of N was determined by measuring ammonium-N and nitrate-N concentrations in leachates during 90 d of incubation. Non-linear regression was used to fit N leaching rate to a first-order model. In all the treated soils, N was released in the order: urea (89%–100%) > IBDU (59%–94%) >UF (46%–73%) > CDU (44%–56%). At the end of incubation, N released from CDU did not differ (P > 0.05) among soils. On the contrary, UF and IBDU released significantly lower (P < 0.05) amounts of N in the soil with higher microbial activity and lower pH.The rate constant (K_0) for UF was lower (P < 0.05) in the soil with lower pH. Taken together, our results indicated that soil microbial size and microbial activity had a marginal effect on fertilizer mineralization.
