There is a need for rice cultivars with high yields and nitrogen(N) use efficiency(NUE), but with low cadmium(Cd) accumulation in Cd-contaminated paddy soils.To determine the relative effects of rice genotype, soil ty...There is a need for rice cultivars with high yields and nitrogen(N) use efficiency(NUE), but with low cadmium(Cd) accumulation in Cd-contaminated paddy soils.To determine the relative effects of rice genotype, soil type, and Cd addition on rice grain yield and NUE, a pot experiment consisting of nine rice cultivars was conducted in two types of paddy soils, red soil(RS) and yellow soil(YS),without or with Cd spiked at 0.6 mg kg^(-1).The N supply was from both soil organic N pools and N fertilizers; thus, NUE was defined as the grain yield per unit of total crop-available N in the soil.Cd addition decreased grain yield and NUE in most rice cultivars,which was mainly related to reduced N uptake efficiency(NpUE, defined as the percentage of N taken up by the crop per unit of soil available N).However, Cd addition enhanced N assimilation efficiency(NtUE, defined as the grain yield per unit of N taken up by the crop) by 21.9% on average in all rice cultivars.The NpUE was mainly affected by soil type, whereas NtUE was affected by rice cultivar.Hybrid cultivars had higher NUEs than the japonica and indica cultivars because of their greater biomass and higher tolerance to Cd contamination.Reduction of NUE after Cd addition was stronger in RS than in YS, which was related to the lower absorption capacity for Cd in RS.Canonical correspondence analysis-based variation partitioning showed that cultivar type had the largest effect(34.4%) on NUE, followed by Cd addition(15.2%) and soil type(10.0%).展开更多
Nitrification inhibitors are widely used in agriculture to mitigate nitrous oxide(N_(2)O)emission and increase crop yield.However,no concrete information on their mitigation of N_(2)O emission is available under soil ...Nitrification inhibitors are widely used in agriculture to mitigate nitrous oxide(N_(2)O)emission and increase crop yield.However,no concrete information on their mitigation of N_(2)O emission is available under soil and environmental conditions as in Pakistan.A field experiment was established using a silt clay loam soil from Peshawar,Pakistan,to study the effect of urea applied in combination with a nitrification inhibitor,nitrapyrin(2-chloro-6-tri-chloromethyl pyridine),and/or a plant growth regulator,gibberellic acid(GA_3),on N_(2)O emission and the nitrogen(N)uptake efficiency of maize.The experimental design was a randomized complete block with five treatments in four replicates:control with no N(CK),urea(200 kg N ha^(-1))alone,urea in combination with nitrapyrin(700 g ha^(-1)),urea in combination with GA_3(60 g ha^(-1)),and urea in combination with nitrapyrin and GA_3.The N_(2)O emission,yield,N response efficiency,and total N uptake were measured during the experimental period.The treatment with urea and nitrapyrin reduced total N_(2)O emission by 39%–43%and decreased yield-scaled N_(2)O emission by 47%–52%,relative to the treatment with urea alone.The maize plant biomass,grain yield,and total N uptake increased significantly by 23%,17%,and 15%,respectively,in the treatment with urea and nitrapyrin,relative to the treatment with urea alone,which was possibly due to N saving,lower N loss,and increased N uptake in the form of ammonium;they were further enhanced in the treatment with urea,nitrapyrin,and GA_3 by 27%,36%,and 25%,respectively,probably because of the stimulating effect of GA_3 on plant growth and development and the reduction in biotic and abiotic stresses.These results suggest that applying urea in combination with nitrapyrin and GA_3 has the potential to mitigate N_(2)O emission,improve N response efficiency,and increase maize yield.展开更多
Split fertilization strategy is popularly adopted in rice to synchronize soil nitrogen(N) supply and crop N demand. Attention has been paid more on mid-season topdressing N, but limited on basal N. A clearer understan...Split fertilization strategy is popularly adopted in rice to synchronize soil nitrogen(N) supply and crop N demand. Attention has been paid more on mid-season topdressing N, but limited on basal N. A clearer understanding of the basal N fate under split fertilization is crucial for determining rational basal N split ratio to improve the yield and reduce the loss to environment. A two-year field experiment with two N rates of 150 and 300 kg Nha^(-1), two split ratios of basal N, 40% and 25%, and two rice varieties,Wuyunjing 23(japonica) and Y-liangyou 2(super hybrid indica), was conducted. Labelled ^(15) N urea was supplied in micro-plots as basal fertilizer to determine the plant uptake, translocation, soil residual, and loss of basal N fertilizer. The results showed that basal N absorbed by rice was only 1.6%–11.5% before tillering fertilization(8–10 d after transplanting), 6.5%–21.4% from tillering fertilization to panicle fertilization, and little(0.1%–4.4%) after panicle fertilization. The recovery efficiency of basal N for the entire rice growth stage was low and ranged from 18.7% to 24.8%, not significantly affected by cultivars or N treatments. Soil residual basal N accounted for 10.3%–36.4% and decreased with increasing total N rate and basal N ratio, regardless of variety and year. 43.8%–70.4% of basal N was lost into the environment based on the N balance. Basal N loss was significantly linearly positive related with the basal N rate and obviously enhanced by the increasing basal N ratio for both varieties in both 2012 and 2013. The N use efficiency and yield was significantly improved when decreasing the basal N ratio from 40% to 25%. The results indicated that the basal N ratio should be reduced, especially with limited N inputs, to improve the yield and reduce the N loss to the environment.展开更多
Point placement of urea is an efficient technology to improve urea use efficiency in transplanted rice(Oryza sativa L.), but it is largely unknown how nutrient composition in the point placement and the distance from ...Point placement of urea is an efficient technology to improve urea use efficiency in transplanted rice(Oryza sativa L.), but it is largely unknown how nutrient composition in the point placement and the distance from placement site to the plant influence rice root distribution and growth, nutrient uptake, and rice grain yield. A controlled greenhouse experiment was conducted using both N-and P-deficient soil with point placement of N only or N and P together(N + P) at a distance close to or far from the plant,in comparison to an N-spilt application and a no-N control. Both nutrient composition and distance significantly affected rice root growth. Compared with the N point placement, the N + P point placement led to smaller root length and mass densities, higher specific root length(SRL) around the placement site, smaller root system, higher straw mass and grain yield, and higher N and P uptake. The difference between the N + P and N point placements was greater when close to the plant than when far from the plant. It is suggested that higher SRL around the placement site is essential for improving nutrient uptake and rice grain yield, and simultaneous point placement of N and P has a synergistic effect on rice growth.展开更多
基金supported by the Modern Agricultural Industry Technology System of the Ministry of Agriculture of China(No.CARS-22-G-14)the Science and Technology Service Network Initiative of Chinese Academy of Sciences(No.KFJ-SW-STS-142)
文摘There is a need for rice cultivars with high yields and nitrogen(N) use efficiency(NUE), but with low cadmium(Cd) accumulation in Cd-contaminated paddy soils.To determine the relative effects of rice genotype, soil type, and Cd addition on rice grain yield and NUE, a pot experiment consisting of nine rice cultivars was conducted in two types of paddy soils, red soil(RS) and yellow soil(YS),without or with Cd spiked at 0.6 mg kg^(-1).The N supply was from both soil organic N pools and N fertilizers; thus, NUE was defined as the grain yield per unit of total crop-available N in the soil.Cd addition decreased grain yield and NUE in most rice cultivars,which was mainly related to reduced N uptake efficiency(NpUE, defined as the percentage of N taken up by the crop per unit of soil available N).However, Cd addition enhanced N assimilation efficiency(NtUE, defined as the grain yield per unit of N taken up by the crop) by 21.9% on average in all rice cultivars.The NpUE was mainly affected by soil type, whereas NtUE was affected by rice cultivar.Hybrid cultivars had higher NUEs than the japonica and indica cultivars because of their greater biomass and higher tolerance to Cd contamination.Reduction of NUE after Cd addition was stronger in RS than in YS, which was related to the lower absorption capacity for Cd in RS.Canonical correspondence analysis-based variation partitioning showed that cultivar type had the largest effect(34.4%) on NUE, followed by Cd addition(15.2%) and soil type(10.0%).
基金funded by the International Atomic Energy Agency through a Coordinated Research Project(CRP D1.50.16)“Minimizing Farming Impacts on Climate Change by Enhancing Carbon and Nitrogen Capture and Storage in Agro-Ecosystems”(18595)of Soil and Water Management and Crop Nutrition Section,Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture,Department of Nuclear Sciences and Applications。
文摘Nitrification inhibitors are widely used in agriculture to mitigate nitrous oxide(N_(2)O)emission and increase crop yield.However,no concrete information on their mitigation of N_(2)O emission is available under soil and environmental conditions as in Pakistan.A field experiment was established using a silt clay loam soil from Peshawar,Pakistan,to study the effect of urea applied in combination with a nitrification inhibitor,nitrapyrin(2-chloro-6-tri-chloromethyl pyridine),and/or a plant growth regulator,gibberellic acid(GA_3),on N_(2)O emission and the nitrogen(N)uptake efficiency of maize.The experimental design was a randomized complete block with five treatments in four replicates:control with no N(CK),urea(200 kg N ha^(-1))alone,urea in combination with nitrapyrin(700 g ha^(-1)),urea in combination with GA_3(60 g ha^(-1)),and urea in combination with nitrapyrin and GA_3.The N_(2)O emission,yield,N response efficiency,and total N uptake were measured during the experimental period.The treatment with urea and nitrapyrin reduced total N_(2)O emission by 39%–43%and decreased yield-scaled N_(2)O emission by 47%–52%,relative to the treatment with urea alone.The maize plant biomass,grain yield,and total N uptake increased significantly by 23%,17%,and 15%,respectively,in the treatment with urea and nitrapyrin,relative to the treatment with urea alone,which was possibly due to N saving,lower N loss,and increased N uptake in the form of ammonium;they were further enhanced in the treatment with urea,nitrapyrin,and GA_3 by 27%,36%,and 25%,respectively,probably because of the stimulating effect of GA_3 on plant growth and development and the reduction in biotic and abiotic stresses.These results suggest that applying urea in combination with nitrapyrin and GA_3 has the potential to mitigate N_(2)O emission,improve N response efficiency,and increase maize yield.
基金financially supported by the National Natural Science Foundation of China (No. 41171235)Jiangsu Agriculture Science and Technology Innovation Fund, China (No. CX(13)3040)the Special Fund for Environmental Research in the Public Interest, China (No. 201309035-7)
文摘Split fertilization strategy is popularly adopted in rice to synchronize soil nitrogen(N) supply and crop N demand. Attention has been paid more on mid-season topdressing N, but limited on basal N. A clearer understanding of the basal N fate under split fertilization is crucial for determining rational basal N split ratio to improve the yield and reduce the loss to environment. A two-year field experiment with two N rates of 150 and 300 kg Nha^(-1), two split ratios of basal N, 40% and 25%, and two rice varieties,Wuyunjing 23(japonica) and Y-liangyou 2(super hybrid indica), was conducted. Labelled ^(15) N urea was supplied in micro-plots as basal fertilizer to determine the plant uptake, translocation, soil residual, and loss of basal N fertilizer. The results showed that basal N absorbed by rice was only 1.6%–11.5% before tillering fertilization(8–10 d after transplanting), 6.5%–21.4% from tillering fertilization to panicle fertilization, and little(0.1%–4.4%) after panicle fertilization. The recovery efficiency of basal N for the entire rice growth stage was low and ranged from 18.7% to 24.8%, not significantly affected by cultivars or N treatments. Soil residual basal N accounted for 10.3%–36.4% and decreased with increasing total N rate and basal N ratio, regardless of variety and year. 43.8%–70.4% of basal N was lost into the environment based on the N balance. Basal N loss was significantly linearly positive related with the basal N rate and obviously enhanced by the increasing basal N ratio for both varieties in both 2012 and 2013. The N use efficiency and yield was significantly improved when decreasing the basal N ratio from 40% to 25%. The results indicated that the basal N ratio should be reduced, especially with limited N inputs, to improve the yield and reduce the N loss to the environment.
基金supported by the Major Sate Basic Research Development Program of China (No. 2013CB127401)the National Science Foundation of China (No. 41271309)the Postdoctoral Science Foundation of Jiangsu (No. 140064C)
文摘Point placement of urea is an efficient technology to improve urea use efficiency in transplanted rice(Oryza sativa L.), but it is largely unknown how nutrient composition in the point placement and the distance from placement site to the plant influence rice root distribution and growth, nutrient uptake, and rice grain yield. A controlled greenhouse experiment was conducted using both N-and P-deficient soil with point placement of N only or N and P together(N + P) at a distance close to or far from the plant,in comparison to an N-spilt application and a no-N control. Both nutrient composition and distance significantly affected rice root growth. Compared with the N point placement, the N + P point placement led to smaller root length and mass densities, higher specific root length(SRL) around the placement site, smaller root system, higher straw mass and grain yield, and higher N and P uptake. The difference between the N + P and N point placements was greater when close to the plant than when far from the plant. It is suggested that higher SRL around the placement site is essential for improving nutrient uptake and rice grain yield, and simultaneous point placement of N and P has a synergistic effect on rice growth.
