华中区域直播冬油菜临界氮浓度稀释曲线的建立与应用

【目的】明确华中区域直播冬油菜的氮素稀释曲线模型及其适用性,探讨以氮素营养指数评价油菜氮素营养状况的可行性。【方法】通过2015—2016和2016—2017两个年度设置的不同氮肥用量（2015—2016年度氮肥用量为0、60、120、180和240 kg N·hm ^-2,2016—2017年度氮肥用量为0、60、120、180、240、300和360 kg N·hm ^-2）的田间试验,研究不同氮肥用量下从苗期到花期油菜各生育时期地上部生物量和植株氮素含量变化,建立直播冬油菜地上部临界氮素浓度稀释曲线模型。并利用该模型和植株氮素含量计算氮素营养指数,明确氮肥用量对油菜植株各个时期氮素营养指数的影响,探究油菜产量和氮素营养指数的关系,确定各时期适宜的氮素营养指数。 【结果】氮肥施用显著增加油菜地上部生物量和氮素含量,不同氮肥处理间差异显著。直播冬油菜地上部临界氮素浓度和地上部生物量符合幂指数的关系（Ncnc=3.49DM ^-0.26）。该模型可以将独立的两个试验的氮限制和非氮限制组数据区分开,模型拟合的氮素浓度和植株实际氮素浓度线性相关,RMSE和n-RMSE分别为0.37和13%,模型具有较好的稳定性。在试验氮肥用量范围内,各点不同时期氮素营养指数随氮肥用量的增加而增加,且氮素营养指数对氮肥用量的响应与产量相似。氮肥施用显著增加油菜产量,尽管不同试验点直播冬油菜产量对氮肥用量的响应存在差异,但各点相对产量和不同时期的氮素营养指数均呈一元二次曲线关系,各生育时期氮素营养指数可以准确地反映油菜氮素营养状况。直播冬油菜相对产量为1时,越冬期、薹期和花期的氮素营养指数分别为1.35、1.26和1.03。 【结论】油菜氮素稀释曲线模型Ncnc=3.49DM ^-0.26和氮营养指数能够评价华中区域直播冬油菜氮素营养状况,用于植株氮素诊断。     

Nitrogen Nutrition Index and Its Relationship with N Use Efficiency,Tuber Yield,Radiation Use Efficiency,and Leaf Parameters in Potatoes

Knowledge about crop growth processes in relation to N limitation is necessary to optimize N management in farming system. Plant-based diagnostic method, for instance nitrogen nutrition index (NNI) were used to determine the crop nitrogen status. This study determines the relationship of NNI with agronomic nitrogen use efficiency (AE_N), tuber yield, radiation use efficiency (RUE) and leaf parameters including leaf area index (LAI), areal leaf N content (N_AL) and leaf N concentration (N_L). Potatoes were grown in field at three N levels: no N (N1), 150 kg N ha⁻¹ (N2), 300 kg N ha⁻¹ (N3). N deficiency was quantified by NNI and RUE was generally calculated by estimating of the light absorbance on leaf area. NNI was used to evaluate the N effect on tuber yield, RUE, LAI, N_AL, and N_L. The results showed that NNI was negatively correlated with AE_N, N deficiencies (NNI<1) which occurred for N1 and N2 significantly reduced LAI, N_L and tuber yield; whereas the N deficiencies had a relative small effect on N_AL and RUE. To remove any effect other than N on these parameters, the actual ratio to maximum values were calculated for each developmental stage of potatoes. When the NNI ranged from 0.4 to 1, positive linear relationships were obtained between NNI and tuber yield, LAI, N_L, while a nonlinear regression fitted the response of RUE to NNI.     

Leaf area index based nitrogen diagnosis in irrigated lowland rice

Leaf area index(LAI)is used for crop growth monitoring in agronomic research,and is promising to diagnose the nitrogen(N)status of crops.This study was conducted to develop appropriate LAI-based N diagnostic models in irrigated lowland rice.Four field experiments were carried out in Jiangsu Province of East China from 2009 to 2014.Different N application rates and plant densities were used to generate contrasting conditions of N availability or population densities in rice.LAI was determined by LI-3000,and estimated indirectly by LAI-2000 during vegetative growth period.Group and individual plant characters(e.g.,tiller number(TN)and plant height(H))were investigated simultaneously.Two N indicators of plant N accumulation(NA)and N nutrition index(NNI)were measured as well.A calibration equation(LAI=1.7787LAI_(2000)–0.8816,R~2=0.870~(**))was developed for LAI-2000.The linear regression analysis showed a significant relationship between NA and actual LAI(R~2=0.863~(**)).For the NNI,the relative LAI(R~2=0.808~(**))was a relatively unbiased variable in the regression than the LAI(R~2=0.33~(**)).The results were used to formulate two LAI-based N diagnostic models for irrigated lowland rice(NA=29.778LAI–5.9397;NNI=0.7705RLAI+0.2764).Finally,a simple LAI deterministic model was developed to estimate the actual LAI using the characters of TN and H(LAI=–0.3375(TH×H×0.01)~2+3.665(TH×H×0.01)–1.8249,R~2=0.875~(**)).With these models,the N status of rice can be diagnosed conveniently in the field.     

An entirely new approach based on remote sensing data to calculate the nitrogen nutrition index of winter wheat

The nitrogen nutrition index(NNI) is a reliable indicator for diagnosing crop nitrogen(N) status. However, there is currently no specific vegetation index for the NNI inversion across multiple growth periods. To overcome the limitations of the traditional direct NNI inversion method(NNI_(T1)) of the vegetation index and traditional indirect NNI inversion method(NNI_(T2)) by inverting intermediate variables including the aboveground dry biomass(AGB) and plant N concentration(PNC), this study proposed a new NNI remote sensing index(NNI_(RS)). A remote-sensing-based critical N dilution curve(Nc_(_RS)) was set up directly from two vegetation indices and then used to calculate NNI_(RS). Field data including AGB, PNC, and canopy hyperspectral data were collected over four growing seasons(2012–2013(Exp.1), 2013–2014(Exp. 2), 2014–2015(Exp. 3), 2015–2016(Exp. 4)) in Beijing, China. All experimental datasets were cross-validated to each of the NNI models(NNI_(T1), NNI_(T2) and NNI_(RS)). The results showed that:(1) the NNI_(RS) models were represented by the standardized leaf area index determining index(sLAIDI) and the red-edge chlorophyll index(CI_(red edge)) in the form of NNI_(RS)=CI_(red edge)/(a×sLAIDI~b), where "a" equals 2.06, 2.10, 2.08 and 2.02 and "b" equals 0.66, 0.73, 0.67 and 0.62 when the modeling set data came from Exp.1/2/4, Exp.1/2/3, Exp.1/3/4, and Exp.2/3/4, respectively;(2) the NNI_(RS) models achieved better performance than the other two NNI revised methods, and the ranges of R2 and RMSE were 0.50–0.82 and 0.12–0.14, respectively;(3) when the remaining data were used for verification, the NNI_(RS) models also showed good stability, with RMSE values of 0.09, 0.18, 0.13 and 0.10, respectively. Therefore, it is concluded that the NNI_(RS) method is promising for the remote assessment of crop N status.     

Determining nitrogen status and quantifying nitrogen fertilizer requirement using a critical nitrogen dilution curve for hybrid indica rice under mechanical pot-seedling transplanting pattern

Field experiments of nitrogen(N) treatment at five different application rates(0, 75, 150, 225, and 300 kg ha~(-1)) were conducted under pot-seedling mechanical transplanting(PMT) in 2018 and 2019. Two high-quality and high-yielding hybrids of indica rice, Huiliangyou 898 and Y Liangyou 900, were used in this study. The N nutrition index(NNI) and accumulated N deficit(N_(and)), used to assess the N nutrition status in real-time, were calculated for the indica cultivars under PMT with a critical nitrogen concentration(N_c) dilution model based on shoot dry matter(DM) during the whole rice growth stage. The relationships between NNI and N_(and) with relative yield(RY) were determined, and accurate N application schemes were developed for hybrids indica rice under PMT. The results indicated that high application rate of N-fertilizer significantly increased the concentrations of shoot DM and N in aboveground organs during the observed stages in the two cultivars for two years(P0.05). The N_c dilution model of hybrid indica cultivars was N_c=4.02 DM~(-0.42)(R~2=0.97) combining the two cultivars under PMT. Root-mean-square error and normalized root-mean-square error of the curve verification were 0.23 and 10.61%, respectively. The NNI and N_(and) ranged from 0.58 to 1.31 and 109 to –55 kg ha~(-1), respectively, in the two cultivars for all N treatments. NNI showed a linear relationship with N_(and) during the entire growth stage(0.53R~20.99, P0.01). In addition, NNI showed a linear-plateau relationship with RY(0.73R~20.92, P0.01) throughout the observed stages. These results suggest that the models can accurately diagnose the N-nutrition status and support effective N-fertilizer management in real-time for hybrid indica rice under PMT.     

氮磷配施下夏玉米临界氮浓度稀释曲线的构建与氮营养诊断

[目的]探究不同水平氮磷配施对夏玉米地上部生物量和氮素浓度的影响,构建临界氮浓度稀释曲线模型,并基于氮营养指数模型诊断和评价玉米在不同氮磷互作条件下的氮素营养状况,可为夏玉米氮磷肥合理施用提供理论依据.[方法]以玉米品种郑单958和豫玉22为试验材料,在陕西关中平原设置田间定位氮磷配施试验,设氮肥(N)用量0、75、1...     

Closing the nitrogen use efficiency gap and reducing the environmental impact of wheat-maize cropping on smallholder farms in the Guanzhong Plain,Northwest China

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 N₂O 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 N₂O 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 N₂O emissions were 1.50 and 3.88 kg ha^–1, respectively. High N balance, large Nr losses and elevated N₂O 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 N₂O 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 N₂O emissions for the investigated cropping system in Northwest China.     

不同水氮条件下冬小麦穗器官临界氮稀释模型研究

【目的】 开花后穗部器官成为小麦生长中心,保证穗部充足的氮素营养是籽粒产量和蛋白品质形成的基础,精确诊断穗氮营养对预测评价产量和品质具有重要意义。【方法】 选用周麦27和豫麦49-198为材料,在大田条件下设置3个灌溉条件（W0：雨养、W1：拔节期浇水1次、W2：拔节和开花各浇水1次）和5个施氮水平（0（N0）、90 kg·hm^-2（N6）、180 kg·hm^-2（N12）、270 kg·hm^-2（N18）和360 kg·hm^-2（N24））,于小麦开花后不同的灌浆时段采集各处理小麦穗器官干物质及氮素含量数据,构建不同灌溉条件下冬小麦穗器官的临界氮稀释（Nc）曲线,并于成熟期测定籽粒产量和蛋白质含量。【结果】 在同一灌溉条件下,随着施氮量的增加,穗部干物质及氮含量均增加;不同灌溉条件下的穗部临界氮浓度与生物量间均符合幂指数关系,不同灌溉条件的模型间存在差异（W0: Nc=2.58 DM^-0.242; W1: Nc=2.92 DM^-0.24; W2: Nc=3.10 DM^-0.231）。氮营养指数（NNI）在不同灌溉条件下均随着施氮量的增加而增加,适宜施氮量因灌溉条件而异,雨养条件为180—270 kg·hm^-2,灌溉条件为270 kg·hm^-2左右。相对产量（RY）与NNI之间显著相关,具体表现为线性+平台特征,在雨养条件下NNI为1.01时,RY获得最大值;而在灌溉条件下NNI为0.97时,RY获得最大值。籽粒蛋白含量与NNI之间呈显著的线性定量关系,灌溉导致蛋白质含量有所降低。【结论】 确立的穗器官Nc及NNI模型,能够有效指示不同水氮条件下小麦氮素丰缺变化,实时评价产量状况,准确预测蛋白质含量,为小麦生育后期的田间及收储管理提供参考和依据。     

Effects of nitrogen application rates and irrigation regimes on grain yield and water use efficiency of maize under alternate partial root-zone irrigation

Faced with the scarcity of water resources and irrational fertilizer use, it is critical to supply plants with water and fertilizer in a coordinated pattern to improve yield with high water use efficiency (WUE). One such method, alternate partial root-zone irrigation (APRI), has been practiced worldwide, but there is limited information on the performance of different irrigation regimes and nitrogen (N) rates under APRI. The objectives of this study were to investigate the effects of varying irrigation regimes and N rates on shoot growth, grain yield and WUE of maize (Zea mays L.) grown under APRI in the Hexi Corridor area of Northwest China in 2014 and 2015. The three N rates were 100, 200 and 300 kg N ha⁻¹, designated N₁, N₂ and N₃, respectively. The three irrigation regimes of 45–50%, 60–65% and 75–80% field capacity (FC) throughout the maize growing season, designated W₁, W₂ and W₃, respectively, were applied in combination with each N rate. The results showed that W₂ and W₃ significantly increased the plant height, stem diameter, crop growth rate, chlorophyll SPAD value, net photosynthetic rate (P_n), biomass, grain yield, ears per ha, kernels per cob, 1 000-kernel weight, harvest index, evapotranspiration and leaf area index (LAI) compared to W₁ at each N rate. The N₂ and N₃ treatments increased those parameters compared to N₁ in each irrigation treatment. Increasing the N rate from the N₂ to N₃ resulted in increased biomass and grain yield under W₃ while it had no impact on those under the W₁ and W₂ treatments. The W₃N₃ and W₂N₂ and W₂N₃ treatments achieved the greatest and the second-greatest biomass and grain yield, respectively. Increasing the N rate significantly enhanced the maximum LAI (LAI at the silking stage) and P_n under W₃, suggesting that the interaction of irrigation and fertilizer N management can effectively improve leaf growth and development, and consequently provide high biomass and grain yield of maize. The W₂N₂, W₂N₃ and W₃N₃ treatments attained the greatest WUE among all the treatments. Thus, either 60–65% FC coupled with 200–300 kg N ha⁻¹ or 75–80% FC coupled with 300 kg N ha⁻¹ is proposed as a better pattern of irrigation and nitrogen application with positive regulative effects on grain yield and WUE of maize under APRI in the Hexi Corridor area of Northwest China and other regions with similar environments. These results can provide a basis for in-depth understanding of the mechanisms of grain yield and WUE to supply levels of water and nitrogen.     

不同施氮量下缓释氮肥与尿素掺混对玉米生长与氮素吸收利用的影响

【目的】研究不同施氮量下,尿素与缓释氮肥掺混对大田玉米生长、干物质累积量、产量、氮肥利用率和土壤硝态氮残留的影响,为作物高效施氮管理提供理论依据。【方法】试验选用玉米品种郑单958,设置了3种氮肥类型(尿素(U)、缓释氮肥(S)、尿素缓释肥3∶7掺混(SU))和4个施氮水平(N1(90 kg·hm~(-2))、N2(120 kg·hm~(-2))、N3(180 kg·hm~(-2))、N4(240 kg·hm~(-2))),以不施氮肥(N0)为对照,共13个处理。生育期内对玉米株高、茎粗和叶面积指数进行观测,并统计干物质累积量、产量及产量构成因素。【结果】氮肥类型与施氮量及两者交互作用对玉米生长指标、干物质累积量、产量及产量构成要素都有显著的影响。尿素掺混缓释氮肥(SU)在N3施氮量下玉米最大干物质累积量和氮素累积吸收量分别为17 927.9 kg·hm~(-2)和156.1 kg·hm~(-2),较其他处理分别提高了16.0%—61.7%和8.1%—45.2%。尿素掺混缓释氮肥(SU)在N3施氮量下,产量达到最高,为6 200 kg·hm~(-2),比尿素(U)N3处理和缓释氮肥(S)N2处理的产量分别增加了19.8%和20.7%;其中,缓释氮肥处理(S)和尿素掺混缓释氮肥处理(SU)在N2施氮量下比尿素处理施氮量减少30%时,产量无显著性差异。玉米的产量并不是随着施氮量的增加而增加,尿素(U)和尿素掺混缓释氮肥处理(SU)在N3施氮量时玉米产量比N4施氮量分别增加了19.7%和19.0%,缓释氮肥处理(S)中N2施氮量的玉米产量比N3和N4施氮量分别提高10.9%和26.5%。尿素掺混缓释氮肥(SU)N3处理玉米吐丝期后营养器官中氮素向籽粒中转运量最大,比尿素(U)N3处理和缓释氮肥(S)N2处理分别增加了14.7%和8.2%,有利于促进籽粒的增产。土壤硝态氮的累积量随着施氮量的增加而增加,但是尿素掺混缓释氮肥(SU)处理的土壤硝态氮累积量比尿素(U)处理和缓释氮肥(S)处理分别平均减少21.2%和9.5%,尿素掺混缓释氮肥(SU)处理土壤硝态氮含量主要分布在0—40 cm土层,不仅促进玉米的吸收,更减少土壤氮素向更深土层的淋失,提高耕作层的土壤养分。【结论】尿素与缓释氮肥掺混,施氮量180 kg·hm~(-2)是试验区玉米高效生产的最佳施氮量。     

东北地区春玉米临界氮浓度稀释曲线的建立和验证

过量施氮是目前玉米栽培中存在的普遍现象,基于临界氮浓度稀释曲线计算得出的氮营养指数是诊断氮营养丰缺的重要手段。基于东北地区4个生态点的试验数据,构建了东北地区春玉米临界氮稀释曲线,并在此基础上建立了氮营养指数模型和需氮量模型,结果表明,东北地区春玉米地上部临界氮浓度与生物量符合幂函数关系。利用独立试验资料对建立的临界氮浓度稀释曲线进行检验,发现基于临界氮浓度稀释模型计算的氮营养指数可以准确诊断玉米植株的氮营养状况,并计算出实时的氮素需求量。该研究建立的东北地区春玉米临界氮稀释模型可以为该地区春玉米的氮营养诊断和动态调控提供较好的理论和技术指导。     

滴灌冬小麦地上部干物质积累与分配模型

为构建新疆维吾尔自治区南疆滴灌冬小麦地上部干物质积累规律及其分配模型,通过分析氮素调控的小区试验数据,采用统计模型技术建立基于相对生长度日(RDDT)的冬小麦群体和个体地上部相对干物质积累(RDMA)动态和基于分配指数的各器官物质分配动态的模拟模型,运用水分调控试验数据对模型进行检验。结果表明:滴灌冬小麦返青后干物质积累(DMA)呈典型的"S"型曲线变化趋势,增加水和氮供应量明显促进群体和个体干物质积累量,且灌水效应大于施氮效应,说明在塔里木盆地西北边缘的极端干旱地区保证水分供应的基础上适当增施氮肥是促进小麦生长的关键。各处理DMA的变异系数群体为3.45%～5.19%,个体为2.03%～3.91%,表明群体效应大于个体效应。筛选并构建基于归一化的返青后以RDDT为变量的滴灌冬小麦群、个体RDMA预测模型(MMF):GRDMA_i=(0.001 2+1.003 2RDDT~(4.193 6))/(0.012 9+RDDT~(4.193 6))和SRDMA_i=(0.001 2+1.011 3RDDT~(4.691 1))/(0.018 9+RDDT~(4.691 1)),模拟准确度在0.988 4～1.027 4;以及地上部各器官干物质的分配指数模型,模拟准确度为0.977 5～1.035 4,表明基于RDDT和分配指数的冬小麦群、个体干物质积累和分配模型具有较好的预测性和实用性。     

氮钾配施下施磷对冬小麦群体发育特性、冠层光截获及产量的影响

【目的】明确一定氮钾配施条件下不同施磷水平对冬小麦群体发育特性、冠层截获光合有效辐射(IPAR)及产量的影响,同时分析IPAR与LAI之间的相关性,为在一定氮钾配施下筛选出适宜的磷肥用量提供理论依据。【方法】以郑麦7698为试验材料,设低氮低钾N_1K_1(N 225 kg·hm~(-2)、K_2O 150 kg·hm~(-2))、低氮高钾N_1K2(N 225 kg·hm~(-2)、K_2O 225 kg·hm~(-2))、高氮低钾N_2K_1(N 300 kg·hm~(-2)、K_2O 150 kg·hm~(-2))、高氮高钾N_2K_2(N 300 kg·hm~(-2)、K_2O 225 kg·hm~(-2))4个氮钾配施比例,每个氮钾配施设置5个施磷水平:P0(不施磷)、P1(P_2O_5 150 kg·hm~(-2))、P_2(P_2O_5 225 kg·hm~(-2))、P~(-2)3(P_2O_5 300 kg·hm2)、P4(P_2O_5 375 kg·hm-),共20个处理。对小麦群体动态、叶面积指数(LAI)、开花后干物质积累、冠层截获光合有效辐射(IPAR)、产量等指标进行测定分析。【结果】(1)在4种氮钾配施下,施P_2O_5 0—225 kg·hm~(-2)时,随施磷量的增加,总茎蘖数、开花后干物质积累及LAI均增加,施P_2O_5超过225 kg·hm~(-2)时,各指标均有所下降,以施P_2O_5 225 kg·hm~(-2)水平群体指标最佳。(2)氮钾配施固定条件下,不同施磷水平小麦冠层截获光合有效辐射值(IPAR)的大小顺序均为P_2P1P3P4P0,且P_2水平IPAR值最高,增幅最大。不同氮钾配施下以N_1K_1条件IPAR增幅最多。(3)4种氮钾配施条件下IPAR与LAI均呈指数正相关关系,N_1K_1、N_1K2、N_2K_1、N_2K_2条件下不同施磷水平小麦IPAR与LAI的拟合系数分别为0.8492、0.8363、0.7321、0.8081。产量与LAI在二阶多项式函数关系上拟合度较好,拟合系数为0.7145。(4)从3个年度各处理产量来看,适当增施磷肥有利于提高小麦的籽粒产量,但磷肥增加到一定程度小麦产量又呈下降趋势,不同氮钾配施下N_1K_1处理产量水平最高,氮钾配施固定条件下,不同施磷水平的产量及增产率均为P_2(P_2O_5 225 kg·hm~-2))时最高。【结论】本研究条件下,N_1K_1P_2(N_225 kg·hm~(-2)、K_2O 150 kg·hm~(-2)、P_2O_5 225 kg·hm~(-2))处理可以优化小麦群体结构,提高LAI,增加开花后干物质积累,提高IPAR和籽粒产量。     

优化氮肥配置提高冬小麦-夏玉米贮墒旱作栽培水氮利用效率

为探明与冬小麦-夏玉米周年贮墒旱作节水栽培模式相配套的氮肥高效施用技术,基于贮墒旱作栽培(冬小麦和夏玉米灌底墒水或出苗水,生育期内不灌水),在全年施氮量360 kg/hm2下开展了前后茬作物施氮量配比不同的大田试验.试验设置4种施氮处理,分别为冬小麦120 kg/hm2+夏玉米240 kg/hm2(W0N1);冬小麦1...     

吨粮田肥力指标及培肥措施研究

通过研究,提出了关中灌区吨粮田土壤肥力指标及面积分布预估,得出一年两熟玉米和小麦的最佳施肥量分别为Ｎ１９４．７ｋｇ／ｈｍ＾２,Ｐ２Ｏ５９０．６ｋｇ／ｈｍ＾２和Ｎ１６２ｋｇ／ｈｍ＾２,Ｐ２Ｏ５１３２．７５ｋｇ／ｈｍ＾２;玉米以马鞍式施肥增产显著;     

Nitrogen nutrition diagnosis for cotton under mulched drip irrigation using unmanned aerial vehicle multispectral images

Remote sensing has been increasingly used for precision nitrogen management to assess the plant nitrogen status in a spatial and real-time manner. The nitrogen nutrition index (NNI) can quantitatively describe the nitrogen status of crops. Nevertheless, the NNI diagnosis for cotton with unmanned aerial vehicle (UAV) multispectral images has not been evaluated yet. This study aimed to evaluate the performance of three machine learning models, i.e., support vector machine (SVM), back propagation neural network (BPNN), and extreme gradient boosting (XGB) for predicting canopy nitrogen weight and NNI of cotton over the whole growing season from UAV images. The results indicated that the models performed better when the top 15 vegetation indices were used as input variables based on their correlation ranking with nitrogen weight and NNI. The XGB model performed the best among the three models in predicting nitrogen weight. The prediction accuracy of nitrogen weight at the upper half-leaf level (R²=0.89, RMSE=0.68 g m^–2, RE=14.62% for calibration and R²=0.83, RMSE=1.08 g m^–2, RE=19.71% for validation) was much better than that at the all-leaf level (R²=0.73, RMSE=2.20 g m^–2, RE=26.70% for calibration and R²=0.70, RMSE=2.48 g m^–2, RE=31.49% for validation) and at the plant level (R²=0.66, RMSE=4.46 g m^–2, RE=30.96% for calibration and R²=0.63, RMSE=3.69 g m^–2, RE=24.81% for validation). Similarly, the XGB model (R²=0.65, RMSE=0.09, RE=8.59% for calibration and R²=0.63, RMSE=0.09, RE=8.87% for validation) also outperformed the SVM model (R²=0.62, RMSE=0.10, RE=7.92% for calibration and R²=0.60, RMSE=0.09, RE=8.03% for validation) and BPNN model (R²=0.64, RMSE=0.09, RE=9.24% for calibration and R²=0.62, RMSE=0.09, RE=8.38% for validation) in predicting NNI. The NNI predictive map generated from the optimal XGB model can intuitively diagnose the spatial distribution and dynamics of nitrogen nutrition in cotton fields, which can help farmers implement precise cotton nitrogen management in a timely and accurate manner.     

西北半干旱地区不同氮磷配施对玉米生理指标及产量的影响

通过田间小区试验,研究了不同氮磷水平的配合施用对玉米不同生育期的生长速度、叶面积指数(LAI)、净光合速率(Pn)、干物质积累和根/冠比(R/T)的动态变化规律以及对产量的影响.结果表明,在氮肥施用量为300～600 kg/hm2的范围内,随着施氮量的增加,玉米生长速度、叶面积指数(LAI)、净光合速率(Pn)、干物质积累量均随之增加,玉米的穗长、穗粗及穗行数没有明显变化,但穗粒数、穗粒重、百粒重增加,秃尖长度减小,产量增加;施氮量达到750 kg/hm2时,则使生长速度及生理指标下降.增施氮磷肥均能促进根/冠比的增大,但磷肥的促进作用大于氮肥.以处理N3P2(N 600 kg/hm2,P2O5 120 kg/hm2)为玉米施肥的最优氮磷配比.     

测墒补灌和施氮对冬小麦产量及水分、氮素利用效率的影响

【目的】测墒补灌是近年来研究的一种小麦节水灌溉新技术。论文旨在探索测墒补灌与施氮对冬小麦生长的影响,为该区节水、节氮提供依据。【方法】采用漫灌的方式设置测墒补灌和施氮两因素田间试验,补灌设置4个处理,于冬小麦拔节期、开花期依据0-40 cm土层土壤质量含水量进行测墒补灌,补灌至土壤田间持水量的50%（W₁）、60%（W₂）、70%（W₃）、80%（W₄）。施氮设置4个处理,不施氮（N₀）、施纯氮180 kg·hm^-2（N₁₈₀）、240 kg·hm^-2（N₂₄₀）和300 kg·hm^-2（N₃₀₀）。在此处理下研究了测墒补灌和施氮对冬小麦产量及水分、氮素利用效率的影响。【结果】(1)各施氮处理下,补灌量的增加可增加冬小麦籽粒产量,当补灌量至土壤田间持水量的60%-80%范围内时,冬小麦籽粒的增产效应差异不显著。各补灌处理下,当施氮量超过240 kg·hm^-2时籽粒产量无显著性变化。本试验条件下当补灌至土壤田间持水量的60%,施氮量为240 kg·hm^-2时冬小麦籽粒产量达到最高,为8 104.6 kg·hm^-2。(2)增加施氮量和补灌量均可显著增加麦田总耗水量,但当施氮量超过240 kg·hm^-2时,施氮的提高效果不显著。补灌量的增加会显著增加麦田总耗水量,但当补灌至土壤田间持水量60%（W₂）、70%（W₃）时较补灌至80%（W₄）处理显著降低耗水量,说明有利于节约灌水而获得较高产量。(3)相同施氮处理下,补灌量的增加可显著提高冬小麦水分利用效率,当补灌量增至土壤田间持水量的60%时,冬小麦水分利用效率达到最大值,为14.7 kg·hm^-2·mm^-1。相同补灌处理下,增施氮肥可显著提高冬小麦水分利用效率,但施氮量不宜超过240 kg·hm^-2,否则将导致水分利用效率降低。(4)相同施氮处理下,应控制补灌量至土壤田间持水量的60%时冬小麦氮素干物质生产效率及氮素利用效率最高,为60.1 kg·kg^-1、22.4 kg·kg^-1。相同补灌处理下,施氮量应控制在240 kg·hm^-2时可获得较高的氮素干物质利用效率及冬小麦氮素利用效率最高,为63.9 kg·kg^-1、23.5 kg·kg^-1。【结论】本试验条件下当施氮量为240 kg·hm^-2、冬小麦拔节期、开花期补灌至土壤田间持水量的60%时冬小麦籽粒产量、水分利用效率、氮素干物质利用效率、氮素利用效率均最高,为最优的节水、节氮、高产组合,推荐其作为该区域适宜水、氮用量。     

陕西关中不同年代小麦品种产量及氮素吸收利用对土壤肥力的响应

【目的】探讨陕西关中地区小麦品种演替过程中产量及氮效率对土壤肥力的响应。【方法】以20世纪80年代至今关中冬麦区3个代表性小麦主栽品种为材料,以33年长期不同施肥处理构建的土壤肥力水平梯度为平台,研究品种演替和土壤肥力及其交互对作物产量、氮利用效率的影响。供试品种有20世纪80年代品种小偃6号、90年代末品种小偃22和近年品种西农979。长期施肥包括6个处理：不同水平的氮磷化肥配施（N1P1和N2P2）、有机肥与无机肥配施（M1N1P1、M1N2P2、M2N1P1和M2N2P2）,以不施肥为对照（CK）。【结果】在各个肥力水平土壤上,籽粒产量及收获指数均随小麦品种更替而呈现增加的趋势,尤其在高肥力土壤上更为明显。土壤肥力水平的提高显著提高了小麦籽粒产量,其中西农979增产幅度最大（151.0%-610.5%）,其次为小偃22（127.9%-349.7%）,小偃6号增幅最低（148.1%-341.8%）。土壤肥力与品种对小麦籽粒产量及收获指数有显著的交互作用,低肥力条件下,小偃6号籽粒产量高于西农979,高肥力条件下则相反。小麦百公斤籽粒需氮量随品种演替有降低的趋势,但随土壤肥力水平提高有增加的趋势。土壤肥力与品种对百公斤籽粒需氮量也有显著的交互作用。在小麦品种更替过程中氮肥生理效率和农学效率均呈增加的趋势,但随着土壤肥力水平的提高,各品种小麦的氮肥生理效率呈下降的趋势,氮肥农学效率呈先升高后下降的抛物线变化趋势。土壤肥力与品种对小麦氮肥生理效率和农学效率无明显交互作用。【结论】陕西关中小麦品种演替在高肥力以及养分投入充足时不仅表现出单产不断提高,而且氮效率也呈逐步增加的趋势。因此,品种更新的同时还要注重提升土壤肥力,才能保证粮食安全,实现农业生产可持续发展。     

氮磷钾运筹模式对北疆滴灌棉花生长发育和产量的影响

【目的】明确北疆滴灌棉花干物质积累及产量形成对氮磷钾综合运筹的响应特征,为节省氮肥成本提供依据。【方法】以鲁棉研24号为材料,在4种施氮量（506、402.5、299和195.5 kg·hm^-2,分别用N1、N2、N3和N4表示）和蕾期、花铃期4种不同磷钾肥运筹方式（100%+0,25%+75%,50%+50%和75%+25%,分别用PK-M1,PK-M2,PK-M3和PK-M4表示）下进行田间试验。试验期间测定棉花叶面积指数（LAI）、干物质积累、蕾花铃数量及产量等指标。【结果】在相同磷钾运筹方式下,随着施氮量的降低,LAI的Logistic模型K’值表现为先上升后下降趋势,N3比N2处理高5.1%—16.5%,快速增长起始期（t₁）和快速增长结束期（t₂）均为N3处理最晚,且N3处理快速增长期持续时间最长,N3处理比N2处理多2—12 d;N3处理生长特征值GT最高,N2处理次之,N3比N2处理高5.2%—16.7%;干物质积累量在生长前期表现为N1>N2>N3>N4处理,在生长后期表现为N2>N1>N3>N4处理;蕾花铃数在全生育期表现为N2>N3>N1>N4处理;产量相对值在各施氮处理下表现为N2处理最高,N3处理次之,N2处理比N3处理高3.6%—6.5%。在相同施氮量下,LAI的Logistic模型K’值最高为PK-M3处理,最低为PK-M1处理,PK-M3处理比PK-M1处理高20.5%—27.4%;快速增长起始期t₁(2019年除外)和快速增长结束期t₂均为PK-M3最晚,且PK-M3处理快速增长期持续时间（T）最长;PK-M3处理生长特征值（GT）最高,PK-M2处理次之,PK-M3处理比PK-M2处理高13.0%—24.5%;干物质积累量在生长前期表现为PK-M2处理>PK-M3处理>PK-M4处理>PK-M1处理,生长后期表现为PK-M3>PK-M2>PK-M4>PK-M1处理;蕾花铃数在生长前期表现PK-M4>PK-M3>PK-M>PK-M2处理,生长后期表现为PK-M3>PK-M2>PK-M4>PK-M1处理;产量相对值表现为PK-M3处理最高,比其他磷钾处理高5.2%—18.2%。所有处理中,N3PK-M3处理下LAI Logistic模型K’值和GT值最大,T最长,在吐絮期干物质积累量、相对产量值和后期蕾花铃数仅次于N2PK-M3处理,生殖器官干物质分配比例高于其他处理。相关分析表明,LAI在2018年播种后109 d以后和2019年播种后120 d以后与生殖器官干物质、干物质总量和相对产量呈极显著正相关,全生育期生殖器官个数、总干物质积累量、生殖器官干物质与相对产量均为显著或极显著正相关。所有处理中N2PK-M3产量最高,N3PK-M3处理次之,N3PK-M3相对产量仅比N2PK-M3处理降低1.5%。【结论】N3PK-M3处理与农户常规施氮量相比,减少25%的氮肥施用量仍能获得较高产量,可能是由于推迟了棉花后期LAI到达峰值的时期,延缓了LAI下降速率,提高棉花群体干物质生产能力,并促使其向生殖器官转运,且降低蕾铃脱落,保证后期铃数,为产量的形成提供物质基础。因此,本研究认为在蕾期和花铃期各分施50%磷钾肥的条件下,氮肥的施用量可以降低至299 kg·hm^-2,这比农户常规施氮降低25%,以达到减氮稳产、节本增效的目的。