A high crop yield with the minimum possible cost to the environment is generally desirable.However,the complicated relationships among crop production,nitrogen(N) use efficiency and environmental impacts must be clear...A high crop yield with the minimum possible cost to the environment is generally desirable.However,the complicated relationships among crop production,nitrogen(N) use efficiency and environmental impacts must be clearly assessed.We conducted a series of on-farm N application rate experiments to establish the linkage between crop yield and N_2 O emissions in the Guanzhong Plain in Northwest China.We also examined crop yield,partial factor productivity of applied N(PFPN) and reactive N(Nr) losses through a survey of 1 529 and 1 497 smallholder farms that grow wheat and maize,respectively,in the region.The optimum N rates were 175 and 214 kg ha^(-1) for winter wheat and summer maize,respectively,thereby achieving the yields of 6 799 and 7 518 kg ha^(-1),correspondingly,with low N_2 O emissions based on on-farm N rate experiments.Among the smallholder farms,the average N application rates were 215 and 294 kg ha^(-1) season^(-1),thus producing 6 490 and 6 220 kg ha^(-1) of wheat and maize,respectively.The corresponding PFPN values for the two crops were 36.8 and 21.2 kg N kg^(-1),and the total N_2 O emissions were 1.50 and 3.88 kg ha^(-1),respectively.High N balance,large Nr losses and elevated N_2 O emissions could be explained by the overdoses of N application and low grain yields under the current farming practice.The crop yields,N application rates,PFPN and total N_2 O for wheat and maize were 18 and 24% higher,42 and 37% less,75 and 116% higher,and 42 and 47% less,correspondingly,in the high-yield and high-PFPN group than in the average smallholder farms.In conclusion,closing the PFPN gap between the current average and the value for the high-yield and high-PFPN group would increase crop production and reduce Nr losses or the total N_2 O emissions for the investigated cropping system in Northwest China.展开更多
This study investigated the effects of three contrasting soil management regimes and different nutrient treatments on the distribution of water-stable aggregates（〉2, 1–2, 0.5–1, 0.25–0.5, and 〈0.25 mm） and asso...This study investigated the effects of three contrasting soil management regimes and different nutrient treatments on the distribution of water-stable aggregates（〉2, 1–2, 0.5–1, 0.25–0.5, and 〈0.25 mm） and associated soil organic carbon（SOC） and total nitrogen（TN） content in loess soil. A 21-yr long-term experiment was performed, in which soil management regimes include cropland abandonment（Abandonment）, bare fallow（Fallow） and wheat-fallow cropping（Cropping）. Under Cropping, the following nutrient treatments were employed： control（CK, no nutrient input）, nitrogen only（N）, nitrogen and potassium（NK）, phosphorus and potassium（PK）, NP, NPK, and manure（M） plus NPK（MNPK）. Results demonstrated that Abandonment significantly increased the content of soil macro-aggregates（〉0.25 mm） and mean weight diameter（MWD） at 0–10 and 10–20 cm soil horizons compared with Cropping, whereas Fallow yielded lower values of above two parameters. Abandonment increased SOC and TN contents in all aggregate sizes by 17–62% and 6–60%, respectively, at 0–10 cm soil layer compared with Cropping. Conversely, Fallow decreased SOC and TN contents in all aggregates by 7–27% and 7–25%, respectively. Nevertheless, the three soil management regimes presented similar SOC contents in all aggregates at 10–20 cm soil horizon. Only Cropping showed higher TN content in 〉0.5 mm aggregates than the two other regimes. Consequently, Abandonment enhanced the partitioning proportions of SOC and TN in 〉1 mm macro-aggregates, and Fallow promoted these proportions in micro-aggregates compared with Cropping. Under Cropping, long-term fertilization did not affect the distribution of aggregates and MWD values compared with those under CK, except for NPK treatment. Fertilizer treatments enhanced SOC and TN contents in aggregates at all tested soil depths. However, fertilization did not affect the partitioning proportions of SOC and TN contents in all aggregates compared with CK. Comprehensive results showed that different soil management regimes generated varied patterns of SOC and TN sequestration in loess soil. Abandonment enhanced soil aggregation and sequestered high amounts of SOC and TN in macro-aggregates. Long-term amendment of organic manure integrated with NPK maintained soil aggregate stability and improved SOC and TN sequestration in all aggregates in loess soil subjected to dryland farming.展开更多
基金the National Key Research and Development Program of China (2016YFD0800105)
文摘A high crop yield with the minimum possible cost to the environment is generally desirable.However,the complicated relationships among crop production,nitrogen(N) use efficiency and environmental impacts must be clearly assessed.We conducted a series of on-farm N application rate experiments to establish the linkage between crop yield and N_2 O emissions in the Guanzhong Plain in Northwest China.We also examined crop yield,partial factor productivity of applied N(PFPN) and reactive N(Nr) losses through a survey of 1 529 and 1 497 smallholder farms that grow wheat and maize,respectively,in the region.The optimum N rates were 175 and 214 kg ha^(-1) for winter wheat and summer maize,respectively,thereby achieving the yields of 6 799 and 7 518 kg ha^(-1),correspondingly,with low N_2 O emissions based on on-farm N rate experiments.Among the smallholder farms,the average N application rates were 215 and 294 kg ha^(-1) season^(-1),thus producing 6 490 and 6 220 kg ha^(-1) of wheat and maize,respectively.The corresponding PFPN values for the two crops were 36.8 and 21.2 kg N kg^(-1),and the total N_2 O emissions were 1.50 and 3.88 kg ha^(-1),respectively.High N balance,large Nr losses and elevated N_2 O emissions could be explained by the overdoses of N application and low grain yields under the current farming practice.The crop yields,N application rates,PFPN and total N_2 O for wheat and maize were 18 and 24% higher,42 and 37% less,75 and 116% higher,and 42 and 47% less,correspondingly,in the high-yield and high-PFPN group than in the average smallholder farms.In conclusion,closing the PFPN gap between the current average and the value for the high-yield and high-PFPN group would increase crop production and reduce Nr losses or the total N_2 O emissions for the investigated cropping system in Northwest China.
基金financially supported by the Special Fund for Agro-scientific Research in the Public Interest of China(201203030)the Agricultural Scientific Research Talent and Team Program of China
文摘This study investigated the effects of three contrasting soil management regimes and different nutrient treatments on the distribution of water-stable aggregates（〉2, 1–2, 0.5–1, 0.25–0.5, and 〈0.25 mm） and associated soil organic carbon（SOC） and total nitrogen（TN） content in loess soil. A 21-yr long-term experiment was performed, in which soil management regimes include cropland abandonment（Abandonment）, bare fallow（Fallow） and wheat-fallow cropping（Cropping）. Under Cropping, the following nutrient treatments were employed： control（CK, no nutrient input）, nitrogen only（N）, nitrogen and potassium（NK）, phosphorus and potassium（PK）, NP, NPK, and manure（M） plus NPK（MNPK）. Results demonstrated that Abandonment significantly increased the content of soil macro-aggregates（〉0.25 mm） and mean weight diameter（MWD） at 0–10 and 10–20 cm soil horizons compared with Cropping, whereas Fallow yielded lower values of above two parameters. Abandonment increased SOC and TN contents in all aggregate sizes by 17–62% and 6–60%, respectively, at 0–10 cm soil layer compared with Cropping. Conversely, Fallow decreased SOC and TN contents in all aggregates by 7–27% and 7–25%, respectively. Nevertheless, the three soil management regimes presented similar SOC contents in all aggregates at 10–20 cm soil horizon. Only Cropping showed higher TN content in 〉0.5 mm aggregates than the two other regimes. Consequently, Abandonment enhanced the partitioning proportions of SOC and TN in 〉1 mm macro-aggregates, and Fallow promoted these proportions in micro-aggregates compared with Cropping. Under Cropping, long-term fertilization did not affect the distribution of aggregates and MWD values compared with those under CK, except for NPK treatment. Fertilizer treatments enhanced SOC and TN contents in aggregates at all tested soil depths. However, fertilization did not affect the partitioning proportions of SOC and TN contents in all aggregates compared with CK. Comprehensive results showed that different soil management regimes generated varied patterns of SOC and TN sequestration in loess soil. Abandonment enhanced soil aggregation and sequestered high amounts of SOC and TN in macro-aggregates. Long-term amendment of organic manure integrated with NPK maintained soil aggregate stability and improved SOC and TN sequestration in all aggregates in loess soil subjected to dryland farming.
