Excessive use of nitrogen (N) fertilizers in agricultural systems increases the cost of production and risk of environmental pollution. Therefore, determination of optimum N requirements for plant growth is necessary....Excessive use of nitrogen (N) fertilizers in agricultural systems increases the cost of production and risk of environmental pollution. Therefore, determination of optimum N requirements for plant growth is necessary. Previous studies mostly established critical N dilution curves based on aboveground dry matter (DM) or leaf dry matter (LDM) and stem dry matter (SDM), to diagnose the N nutrition status of the whole plant. As these methods are time consuming, we investigated the more rapidly determined leaf area index (LAI) method to establish the critical nitrogen (Nc) dilution curve, and the curve was used to diagnose plant N status for winter wheat in Guanzhong Plain in Northwest China. Field experiments were conducted using four N fertilization levels (0, 105, 210 and 315 kg ha?1) applied to six wheat cultivars in the 2013–2014 and 2014–2015 growing seasons. LAI, DM, plant N concentration (PNC) and grain yield were determined. Data points from four cultivars were used for establishing the Nc curve and data points from the remaining two cultivars were used for validating the curve. The Nc dilution curve was validated for N-limiting and non-N-limiting growth conditions and there was good agreement between estimated and observed values. The N nutrition index (NNI) ranged from 0.41 to 1.25 and the accumulated plant N deficit (Nand) ranged from 60.38 to –17.92 kg ha?1 during the growing season. The relative grain yield was significantly affected by NNI and was adequately described with a parabolic function. The Nc curve based on LAI can be adopted as an alternative and more rapid approach to diagnose plant N status to support N fertilization decisions during the vegetative growth of winter wheat in Guanzhong Plain in Northwest China.展开更多
A plot experiment including four treatments, CK （N 105 kg ha-1 as urea, including a basal N application of 35 kg ha-I and a topdressing N 70 kg ha-1 at turned green stage） and optimized N management （OPT1, OPT2 and...A plot experiment including four treatments, CK （N 105 kg ha-1 as urea, including a basal N application of 35 kg ha-I and a topdressing N 70 kg ha-1 at turned green stage） and optimized N management （OPT1, OPT2 and OPT3, applied two-thirds, one-third and two-fifths N at jointing stage, respectively, total N 60 kg ha-l）, was conducted to evaluate the effects of nitrogen management on growth and N uptake of winter wheat （Triticum aestivum）, Dongnong 1, which is the first highly cold tolerant winter wheat in China. Index of population quality, N uptake and yield were determined. The ear-bearing tiller rate was increased by above 12%, and the leaf area index, biomass and N uptake were significantly decreased （P〈O.05） at jointing stage. OPT treatments increased the grain to leaf area ratio at heading stage, the dry matter weight and N uptake after heading by 14.3-27.9%, 11.6-28.7% and 118.1-161.8 %, respectively. The yield of the OPT treatments was increased by 14.2-37.5% compared with CK, and there was a significant difference （P〈0.05） between CK and OPT1 treatments. Harvest index and N partial factor productivity （PFP, kg grain yield per kg N applied） was clearly enhanced from 0.4 and 35.6 kg, respectively for CK to an average of 0.48 （P〈0.05） and 77.6 kg （P〈0.05） in the OPT treatments. These results indicated that the optimized N management increased the harvest index, yield and N use efficiency by decreasing the N application rate and postponing N application time, improved wheat population quality, controlled excessive growth in the vegetative stages and increased dry matter and N accumulation rates after heading.展开更多
After water stress at various levels and durations at different growth stages, rewatering could greatly stimulate the leaf area development of winter wheat. The results showed that the stimulation effect changed with ...After water stress at various levels and durations at different growth stages, rewatering could greatly stimulate the leaf area development of winter wheat. The results showed that the stimulation effect changed with water stress time, degree and duration. Rewatering under earlier stress had greater stimulation effect on leaf area than that under later stress. Higher stimulation effect was observed under severe water stress than that under moderate stress. Longer duration of stress resulted in low stimulation effect. In spite of the greater stimulation effect under severe and longer stress, the final leaf area in these situations was lower than that under moderate stress and shorter duration. Whenever the stress occurred, the stimulating effect was due to the increase of the leaf area of the tillers. Once the leaf on the main stem emerged during stress period, rewatering had no effect on its size, and consequently its leaf area. The stimulation of rewateirng on leaf area contributed to the final grain yield by 45% under moderate stress, and 67% under severe stress. Although the stimulation partly compensated for the loss during stress, the final leaf area and the grain yield could not reach the level without water stress.展开更多
Leaf area index （LAI） is an important parameter in a number of models related to ecosystem functioning, carbon budgets, climate, hydrology, and crop growth simulation. Mapping and monitoring the spatial and temporal...Leaf area index （LAI） is an important parameter in a number of models related to ecosystem functioning, carbon budgets, climate, hydrology, and crop growth simulation. Mapping and monitoring the spatial and temporal variations of LAI are necessary for understanding crop growth and development at regional level. In this study, the relationships between LAI of winter wheat and Landsat TM spectral vegetation indices （SVIs） were analyzed by using the curve estimation procedure in North China Plain. The series of LAI maps retrieved by the best regression model were used to assess the spatial and temporal variations of winter wheat LAI. The results indicated that the general relationships between LAI and SVIs were curvilinear, and that the exponential model gave a better fit than the linear model or other nonlinear models for most SVIs. The best regression model was constructed using an exponential model between surface-reflectance-derived difference vegetation index （DVI） and LAI, with the adjusted R2 （0.82） and the RMSE （0.77）. The TM LAI maps retrieved from DVILAI model showed the significant spatial and temporal variations. The mean TM LAI value （30 m） for winter wheat of the study area increased from 1.29 （March 7, 2004） to 3.43 （April 8, 2004）, with standard deviations of 0.22 and 1.17, respectively. In conclusion, spectral vegetation indices from multi-temporal Landsat TM images can be used to produce fine-resolution LAI maps for winter wheat in North China Plain.展开更多
A field experiment was conducted in a manural loesial soil in middle of Shaanxi Province ofChina, a sub-humid area prone to drought, to study the effects of rainwater-harvestingcultivation on water use efficiency (WUE...A field experiment was conducted in a manural loesial soil in middle of Shaanxi Province ofChina, a sub-humid area prone to drought, to study the effects of rainwater-harvestingcultivation on water use efficiency (WUE) and yield of winter wheat. Ridge-furrow tillage wasused, the ridge being mulched by plastic sheets for rainwater harvesting while seeding in thefurrows. Results showed that from sowing to reviving stage of winter wheat, water stored in 0-100 cm layer was significantly decreased whereas that in 100-200 cm layer did not change.Compared to the non-mulching, plastic mulch retained 6.5 mm more water as an average of the twoN rate treatments, having a certain effect on conservation of soil moisture. In contrast, atharvest, water was remarkably reduced in both the 0-100 cm and the 100-200 cm layers, andmulched plots consumed 34.8 mm more water as an average of the two treatments: low N rate (75kg N ha-1) with low plant density (2 300 000 plants ha-1) and high N rate (225 kg N ha-1)with highplant density (2 800 000 plants ha-1), in 0-200 cm layer than those without mulching, the formerbeing beneficial to plants in utilization of deep layer water. Mulching was significant inharvesting water and in increase of yield. Mulched with plastic sheets, biological and grainyields were 22.5 and 22.6% higher for the average of the high N rate than for the low N rate,and the high N rate with low plant density was 29.8 and 29.1% higher in both biological andgrain yields than that of the low N rate with low plant density. With high N rate and high plantdensity, the mulched biological and grain yields were 39.5 and 28.9% higher than the correspondingtreatments without mulching. Of the treatments, that with high N rate and low plant density wasthe highest in both biological and grain yields, and the water use efficiency reached 43.7 kgmm-1 ha-1 for biological yield and 22 kg mm-1 ha-1 for grain yield, being the highest WUE reportedin the world up to now.展开更多
冠气温差能够间接监测作物水分变化规律,而冠层温度与大气温度之间存在的时滞效应会影响监测效果,为探明两者之间的时滞效应变化规律及影响因素,本研究以拔节期至乳熟期的冬小麦为研究对象,利用红外温度传感器连续监测灌溉上限分别为田...冠气温差能够间接监测作物水分变化规律,而冠层温度与大气温度之间存在的时滞效应会影响监测效果,为探明两者之间的时滞效应变化规律及影响因素,本研究以拔节期至乳熟期的冬小麦为研究对象,利用红外温度传感器连续监测灌溉上限分别为田间持水率的95%(T1)、80%(T2)、65%(T3)和50%(T4)4个不同灌溉处理的冠层温度,并同步获取短波净辐射(Short-wave net radiation,R_(S))、大气温度(Atmospheric temperature,T_(A))、相对湿度(Relative humidity,R_(H))等气象数据。利用错位相关法计算冠层温度与大气温度之间的时滞时间(Time lag,TL),分析其在不同生育期和不同灌溉条件下变化规律,并采用相关性分析法探究气象因子(R_(S)、T_(A)、R_(H))变化率和日均值与时滞时间的相关性,最后通过通径分析探讨气象因子(R_(S)、T_(A)、R_(H))、土壤含水率(Soil moisture content,SMC)以及叶面积指数(Leaf area index,LAI)对时滞时间的共同影响。结果表明:不同生育期和不同灌溉条件下冬小麦冠层温度变化均提前于大气温度;在不同灌溉处理下,T1、T2和T3处理的时滞时间高于T4处理,且在不同生育期下,时滞时间呈现先减少再增加的趋势。短波净辐射变化率(Change rate of short-wave net radiation,R_(SCR))、大气温度变化率(Change rate of atmospheric temperature,T_(ACR))和相对湿度变化率(Change rate of relative humidity,R_(HCR))与时滞时间的相关性均高于对应日均值与时滞时间的相关性;同时,R_(SCR)与时滞时间的相关程度最高(相关系数R为0.718~0.806),TACR次之(R为0.582~0.661),RHCR最低(R为-0.534~-0.570)。利用通径分析发现,时滞时间主要受R_(SCR)、SMC以及LAI共同影响,但在不同灌溉条件下影响时滞时间的主要因素存在差异,其中T1、T2和T3处理主要受R_(SCR)和LAI影响,而T4主要受R_(SCR)和SMC影响。研究可为利用冠气温差信息监测作物水分变化进一步提供理论依据。展开更多
基金financial support from the National Key Research and Development Program of China (2017YFC0403303)the Shanxi Agricultural University of Science and Technology Innovation Fund, China (2016YJ07 and 2016007)
文摘Excessive use of nitrogen (N) fertilizers in agricultural systems increases the cost of production and risk of environmental pollution. Therefore, determination of optimum N requirements for plant growth is necessary. Previous studies mostly established critical N dilution curves based on aboveground dry matter (DM) or leaf dry matter (LDM) and stem dry matter (SDM), to diagnose the N nutrition status of the whole plant. As these methods are time consuming, we investigated the more rapidly determined leaf area index (LAI) method to establish the critical nitrogen (Nc) dilution curve, and the curve was used to diagnose plant N status for winter wheat in Guanzhong Plain in Northwest China. Field experiments were conducted using four N fertilization levels (0, 105, 210 and 315 kg ha?1) applied to six wheat cultivars in the 2013–2014 and 2014–2015 growing seasons. LAI, DM, plant N concentration (PNC) and grain yield were determined. Data points from four cultivars were used for establishing the Nc curve and data points from the remaining two cultivars were used for validating the curve. The Nc dilution curve was validated for N-limiting and non-N-limiting growth conditions and there was good agreement between estimated and observed values. The N nutrition index (NNI) ranged from 0.41 to 1.25 and the accumulated plant N deficit (Nand) ranged from 60.38 to –17.92 kg ha?1 during the growing season. The relative grain yield was significantly affected by NNI and was adequately described with a parabolic function. The Nc curve based on LAI can be adopted as an alternative and more rapid approach to diagnose plant N status to support N fertilization decisions during the vegetative growth of winter wheat in Guanzhong Plain in Northwest China.
基金supported by grants from the National Basic Research Program of China (973 Program,2009CB118606)Special Fund for Agro-Scientific Research in the Public Interest, China (201103003)
文摘A plot experiment including four treatments, CK （N 105 kg ha-1 as urea, including a basal N application of 35 kg ha-I and a topdressing N 70 kg ha-1 at turned green stage） and optimized N management （OPT1, OPT2 and OPT3, applied two-thirds, one-third and two-fifths N at jointing stage, respectively, total N 60 kg ha-l）, was conducted to evaluate the effects of nitrogen management on growth and N uptake of winter wheat （Triticum aestivum）, Dongnong 1, which is the first highly cold tolerant winter wheat in China. Index of population quality, N uptake and yield were determined. The ear-bearing tiller rate was increased by above 12%, and the leaf area index, biomass and N uptake were significantly decreased （P〈O.05） at jointing stage. OPT treatments increased the grain to leaf area ratio at heading stage, the dry matter weight and N uptake after heading by 14.3-27.9%, 11.6-28.7% and 118.1-161.8 %, respectively. The yield of the OPT treatments was increased by 14.2-37.5% compared with CK, and there was a significant difference （P〈0.05） between CK and OPT1 treatments. Harvest index and N partial factor productivity （PFP, kg grain yield per kg N applied） was clearly enhanced from 0.4 and 35.6 kg, respectively for CK to an average of 0.48 （P〈0.05） and 77.6 kg （P〈0.05） in the OPT treatments. These results indicated that the optimized N management increased the harvest index, yield and N use efficiency by decreasing the N application rate and postponing N application time, improved wheat population quality, controlled excessive growth in the vegetative stages and increased dry matter and N accumulation rates after heading.
基金National Fundamental Research and Development (No. G1999011709 ) the National Natural Science Foundation (No.49971042).
文摘After water stress at various levels and durations at different growth stages, rewatering could greatly stimulate the leaf area development of winter wheat. The results showed that the stimulation effect changed with water stress time, degree and duration. Rewatering under earlier stress had greater stimulation effect on leaf area than that under later stress. Higher stimulation effect was observed under severe water stress than that under moderate stress. Longer duration of stress resulted in low stimulation effect. In spite of the greater stimulation effect under severe and longer stress, the final leaf area in these situations was lower than that under moderate stress and shorter duration. Whenever the stress occurred, the stimulating effect was due to the increase of the leaf area of the tillers. Once the leaf on the main stem emerged during stress period, rewatering had no effect on its size, and consequently its leaf area. The stimulation of rewateirng on leaf area contributed to the final grain yield by 45% under moderate stress, and 67% under severe stress. Although the stimulation partly compensated for the loss during stress, the final leaf area and the grain yield could not reach the level without water stress.
文摘Leaf area index （LAI） is an important parameter in a number of models related to ecosystem functioning, carbon budgets, climate, hydrology, and crop growth simulation. Mapping and monitoring the spatial and temporal variations of LAI are necessary for understanding crop growth and development at regional level. In this study, the relationships between LAI of winter wheat and Landsat TM spectral vegetation indices （SVIs） were analyzed by using the curve estimation procedure in North China Plain. The series of LAI maps retrieved by the best regression model were used to assess the spatial and temporal variations of winter wheat LAI. The results indicated that the general relationships between LAI and SVIs were curvilinear, and that the exponential model gave a better fit than the linear model or other nonlinear models for most SVIs. The best regression model was constructed using an exponential model between surface-reflectance-derived difference vegetation index （DVI） and LAI, with the adjusted R2 （0.82） and the RMSE （0.77）. The TM LAI maps retrieved from DVILAI model showed the significant spatial and temporal variations. The mean TM LAI value （30 m） for winter wheat of the study area increased from 1.29 （March 7, 2004） to 3.43 （April 8, 2004）, with standard deviations of 0.22 and 1.17, respectively. In conclusion, spectral vegetation indices from multi-temporal Landsat TM images can be used to produce fine-resolution LAI maps for winter wheat in North China Plain.
基金part of the projects(49890330,30230230 and 30070429)supported by the National Natural Science Foundation of China(NSFC)project(G1999011707)supported by the National Key Basic Research Support Funds,China(NKBRSF).
文摘A field experiment was conducted in a manural loesial soil in middle of Shaanxi Province ofChina, a sub-humid area prone to drought, to study the effects of rainwater-harvestingcultivation on water use efficiency (WUE) and yield of winter wheat. Ridge-furrow tillage wasused, the ridge being mulched by plastic sheets for rainwater harvesting while seeding in thefurrows. Results showed that from sowing to reviving stage of winter wheat, water stored in 0-100 cm layer was significantly decreased whereas that in 100-200 cm layer did not change.Compared to the non-mulching, plastic mulch retained 6.5 mm more water as an average of the twoN rate treatments, having a certain effect on conservation of soil moisture. In contrast, atharvest, water was remarkably reduced in both the 0-100 cm and the 100-200 cm layers, andmulched plots consumed 34.8 mm more water as an average of the two treatments: low N rate (75kg N ha-1) with low plant density (2 300 000 plants ha-1) and high N rate (225 kg N ha-1)with highplant density (2 800 000 plants ha-1), in 0-200 cm layer than those without mulching, the formerbeing beneficial to plants in utilization of deep layer water. Mulching was significant inharvesting water and in increase of yield. Mulched with plastic sheets, biological and grainyields were 22.5 and 22.6% higher for the average of the high N rate than for the low N rate,and the high N rate with low plant density was 29.8 and 29.1% higher in both biological andgrain yields than that of the low N rate with low plant density. With high N rate and high plantdensity, the mulched biological and grain yields were 39.5 and 28.9% higher than the correspondingtreatments without mulching. Of the treatments, that with high N rate and low plant density wasthe highest in both biological and grain yields, and the water use efficiency reached 43.7 kgmm-1 ha-1 for biological yield and 22 kg mm-1 ha-1 for grain yield, being the highest WUE reportedin the world up to now.
基金the National Key Basic Research Special Foundation (NKBRSF) of China (No.G2000018603)and the National High Technology Research and Development Program (863 Program) of China (No.2002AA2Z4191).
文摘冠气温差能够间接监测作物水分变化规律,而冠层温度与大气温度之间存在的时滞效应会影响监测效果,为探明两者之间的时滞效应变化规律及影响因素,本研究以拔节期至乳熟期的冬小麦为研究对象,利用红外温度传感器连续监测灌溉上限分别为田间持水率的95%(T1)、80%(T2)、65%(T3)和50%(T4)4个不同灌溉处理的冠层温度,并同步获取短波净辐射(Short-wave net radiation,R_(S))、大气温度(Atmospheric temperature,T_(A))、相对湿度(Relative humidity,R_(H))等气象数据。利用错位相关法计算冠层温度与大气温度之间的时滞时间(Time lag,TL),分析其在不同生育期和不同灌溉条件下变化规律,并采用相关性分析法探究气象因子(R_(S)、T_(A)、R_(H))变化率和日均值与时滞时间的相关性,最后通过通径分析探讨气象因子(R_(S)、T_(A)、R_(H))、土壤含水率(Soil moisture content,SMC)以及叶面积指数(Leaf area index,LAI)对时滞时间的共同影响。结果表明:不同生育期和不同灌溉条件下冬小麦冠层温度变化均提前于大气温度;在不同灌溉处理下,T1、T2和T3处理的时滞时间高于T4处理,且在不同生育期下,时滞时间呈现先减少再增加的趋势。短波净辐射变化率(Change rate of short-wave net radiation,R_(SCR))、大气温度变化率(Change rate of atmospheric temperature,T_(ACR))和相对湿度变化率(Change rate of relative humidity,R_(HCR))与时滞时间的相关性均高于对应日均值与时滞时间的相关性;同时,R_(SCR)与时滞时间的相关程度最高(相关系数R为0.718~0.806),TACR次之(R为0.582~0.661),RHCR最低(R为-0.534~-0.570)。利用通径分析发现,时滞时间主要受R_(SCR)、SMC以及LAI共同影响,但在不同灌溉条件下影响时滞时间的主要因素存在差异,其中T1、T2和T3处理主要受R_(SCR)和LAI影响,而T4主要受R_(SCR)和SMC影响。研究可为利用冠气温差信息监测作物水分变化进一步提供理论依据。
