Aims In the Oregon of USA,the control of western juniper(Juniperus occidentalis)is an accepted rangeland management practice to restore sagebrush steppe habitats of importance to wildlife and livestock.The effects of ...Aims In the Oregon of USA,the control of western juniper(Juniperus occidentalis)is an accepted rangeland management practice to restore sagebrush steppe habitats of importance to wildlife and livestock.The effects of juniper cutting on ecosystem nitrogen,however,have not been well addressed although woody plant control has important implications for local watershed management and regional nitrogen pools.Methods We quantified ecosystem nitrogen stocks in two adjacent watersheds,comprised of a treated watershed(most juniper removed)and an untreated watershed(juniper not removed).Thirteen years after juniper removal,we measured aboveground nitrogen stocks for juniper trees,shrubs,grasses and litter in both watersheds.We also measured belowground nitrogen stocks(roots and soil)in both watersheds at two soil depths(0–25 and 25–50 cm).Important Findings Aboveground nitrogen stocks were 6.9 times greater in the untreated than in the treated watershed considering the much larger aboveground biomass.However,root nitrogen stocks were 3.1 times greater in the treated one due to the gain of understory root biomass associated with juniper cutting.Soil nitrogen stocks at both 0–25 and 25–50 cm depths were not affected by juniper removal.Overall,total ecosystem nitrogen stocks did not differ between the treated(9536 kg N ha−1)and untreated(9456 kg N ha−1)watersheds.The greatest ecosystem nitrogen accumulation(at least 95%total ecosystem nitrogen)resided belowground(soil 0–50 cm and roots)in both watersheds.This study provides evidence that the benefits of juniper removal can be attained without significantly affecting the capacity of ecosystem nitrogen storage.展开更多
Soil organic carbon(SOC)and nitrogen(N)are two of the most important indicators for agricultural productivity.The primary objective of this study was to investigate the changes in SOC and N in the deep soil profile(up...Soil organic carbon(SOC)and nitrogen(N)are two of the most important indicators for agricultural productivity.The primary objective of this study was to investigate the changes in SOC and N in the deep soil profile(up to 100 cm)and their relationships with crop productivity under the influence of long-term(since 1990)fertilization in the wheat-maize cropping system.Treatments included CK(control),NP(inorganic N and phosphorus(P)fertilizers),NPK(inorganic N,P and potassium fertilizers),NPKM(NPK plus manure),and M(manure).Crop yield and the properties of topsoil were measured yearly from 2001 to 2009.C and N contents were measured at five different depths in 2001 and 2009.The results showed that wheat and maize yields decreased between 2001 and 2009 under the inorganic fertilizer(NP and NPK)treatments.The average yield between 2001 and 2009 under the NP,NPK,NPKM,and M treatments(compared with the CK treatment)increased by 38,115,383,and 381%,respectively,for wheat and 348,891,2738,and 1845%,respectively,for maize.Different long-term fertilization treatments significantly changed coarse free particulate(cf POC),fine free particulate(ff POC),intramicroaggregate particulate(i POC),and mineral-associated(m SOC)organic carbon fractions.In the experimental years of 2001 and 2009,soil fractions occurred in the following order for all treatments:m SOC>cf POC>i POC>ff POC.All fractions were higher under the manure application treatments than under the inorganic fertilization treatments.Compared to the inorganic fertilization treatments,manure input enhanced the stocks of SOC and total N in the surface layer(0–20 cm)but decreased SOC and N in the deep soil layer(80–100 cm).This reveals the efficiency of manure in increasing yield productivity and decreasing risk of vertical loss of nutrients,especially N,compared to inorganic fertilization treatments.The findings provide opportunities for understanding deep soil C and N dynamics,which could help mitigate climate change impact on agricultural production and maintain soil health.展开更多
Crop residue retention has been considered a practicable strategy to improve soil organic carbon(SOC)and total nitrogen(TN),but the effectiveness of residue retention might be different under varied tillage practices....Crop residue retention has been considered a practicable strategy to improve soil organic carbon(SOC)and total nitrogen(TN),but the effectiveness of residue retention might be different under varied tillage practices.To evaluate the effects of residue management on the distribution and stocks of SOC and TN under different tillage practices,a bifactorial experiment with three levels for tillage practices(no-tillage,rotary tillage,and conventional tillage)and two levels for residue managements(residue retention and residue removal)was conducted in the North China Plain(NCP).Results showed that after a short experimental duration(3–4 years),concentrations of SOC and TN in the 0–10 cm layer were higher under no-tillage than under conventional tillage,no matter whether crop residues were retained or not.Residue retention increased SOC and TN concentrations in the upper layers of soil to some degree for all tillage practices,as compared with residue removal,with the greatest increment of SOC concentration occurred in the 0–10 cm layer under rotary tillage,but in the 10–30 cm layer under conventional tillage.The stocks of SOC in the 0–50 cm depth increased from 49.89 Mg ha–1 with residue removal to 53.03 Mg ha–1 with residue retention.However,no-tillage did not increase SOC stock to a depth of 50 cm relative to conventional tillage,and increased only by 5.35%as compared with rotary tillage.Thus,residue retention may contribute more towards SOC sequestration than no-tillage.Furthermore,the combination between residue retention and no-tillage has the greatest advantage in enhancing SOC and TN in the NCP region.展开更多
基金This research was supported by Oregon State University and the Oregon Agricultural Experiment Station。
文摘Aims In the Oregon of USA,the control of western juniper(Juniperus occidentalis)is an accepted rangeland management practice to restore sagebrush steppe habitats of importance to wildlife and livestock.The effects of juniper cutting on ecosystem nitrogen,however,have not been well addressed although woody plant control has important implications for local watershed management and regional nitrogen pools.Methods We quantified ecosystem nitrogen stocks in two adjacent watersheds,comprised of a treated watershed(most juniper removed)and an untreated watershed(juniper not removed).Thirteen years after juniper removal,we measured aboveground nitrogen stocks for juniper trees,shrubs,grasses and litter in both watersheds.We also measured belowground nitrogen stocks(roots and soil)in both watersheds at two soil depths(0–25 and 25–50 cm).Important Findings Aboveground nitrogen stocks were 6.9 times greater in the untreated than in the treated watershed considering the much larger aboveground biomass.However,root nitrogen stocks were 3.1 times greater in the treated one due to the gain of understory root biomass associated with juniper cutting.Soil nitrogen stocks at both 0–25 and 25–50 cm depths were not affected by juniper removal.Overall,total ecosystem nitrogen stocks did not differ between the treated(9536 kg N ha−1)and untreated(9456 kg N ha−1)watersheds.The greatest ecosystem nitrogen accumulation(at least 95%total ecosystem nitrogen)resided belowground(soil 0–50 cm and roots)in both watersheds.This study provides evidence that the benefits of juniper removal can be attained without significantly affecting the capacity of ecosystem nitrogen storage.
基金financially supported by the National Key Research and Development Program of China(2016YFD0300901 and 2017YFD0800101)the Fundamental Research Funds for Central Non-profit Scientific Institution,China(161032019035,1610132020022 and 1610132020023)。
文摘Soil organic carbon(SOC)and nitrogen(N)are two of the most important indicators for agricultural productivity.The primary objective of this study was to investigate the changes in SOC and N in the deep soil profile(up to 100 cm)and their relationships with crop productivity under the influence of long-term(since 1990)fertilization in the wheat-maize cropping system.Treatments included CK(control),NP(inorganic N and phosphorus(P)fertilizers),NPK(inorganic N,P and potassium fertilizers),NPKM(NPK plus manure),and M(manure).Crop yield and the properties of topsoil were measured yearly from 2001 to 2009.C and N contents were measured at five different depths in 2001 and 2009.The results showed that wheat and maize yields decreased between 2001 and 2009 under the inorganic fertilizer(NP and NPK)treatments.The average yield between 2001 and 2009 under the NP,NPK,NPKM,and M treatments(compared with the CK treatment)increased by 38,115,383,and 381%,respectively,for wheat and 348,891,2738,and 1845%,respectively,for maize.Different long-term fertilization treatments significantly changed coarse free particulate(cf POC),fine free particulate(ff POC),intramicroaggregate particulate(i POC),and mineral-associated(m SOC)organic carbon fractions.In the experimental years of 2001 and 2009,soil fractions occurred in the following order for all treatments:m SOC>cf POC>i POC>ff POC.All fractions were higher under the manure application treatments than under the inorganic fertilization treatments.Compared to the inorganic fertilization treatments,manure input enhanced the stocks of SOC and total N in the surface layer(0–20 cm)but decreased SOC and N in the deep soil layer(80–100 cm).This reveals the efficiency of manure in increasing yield productivity and decreasing risk of vertical loss of nutrients,especially N,compared to inorganic fertilization treatments.The findings provide opportunities for understanding deep soil C and N dynamics,which could help mitigate climate change impact on agricultural production and maintain soil health.
基金funded by the Special Fund for Agro-Scientific Research in the Public Interest in China (201503136)the National Natural Science Foundation of China (31171510)
文摘Crop residue retention has been considered a practicable strategy to improve soil organic carbon(SOC)and total nitrogen(TN),but the effectiveness of residue retention might be different under varied tillage practices.To evaluate the effects of residue management on the distribution and stocks of SOC and TN under different tillage practices,a bifactorial experiment with three levels for tillage practices(no-tillage,rotary tillage,and conventional tillage)and two levels for residue managements(residue retention and residue removal)was conducted in the North China Plain(NCP).Results showed that after a short experimental duration(3–4 years),concentrations of SOC and TN in the 0–10 cm layer were higher under no-tillage than under conventional tillage,no matter whether crop residues were retained or not.Residue retention increased SOC and TN concentrations in the upper layers of soil to some degree for all tillage practices,as compared with residue removal,with the greatest increment of SOC concentration occurred in the 0–10 cm layer under rotary tillage,but in the 10–30 cm layer under conventional tillage.The stocks of SOC in the 0–50 cm depth increased from 49.89 Mg ha–1 with residue removal to 53.03 Mg ha–1 with residue retention.However,no-tillage did not increase SOC stock to a depth of 50 cm relative to conventional tillage,and increased only by 5.35%as compared with rotary tillage.Thus,residue retention may contribute more towards SOC sequestration than no-tillage.Furthermore,the combination between residue retention and no-tillage has the greatest advantage in enhancing SOC and TN in the NCP region.
