不同氮效率夏玉米临界氮浓度稀释模型与氮营养诊断

【目的】建立豫中地区玉米临界氮稀释曲线,比较不同氮素利用率玉米品种模型差异,探讨基于此的氮营养指数用于诊断、评价玉米氮素营养的可靠性,为实现玉米合理施用氮肥提供理论依据。【方法】以伟科702和中单909两个不同氮利用效率的品种为试验材料进行连续三年的田间定位试验,共设5个氮肥水平(0、120、180、240和360 kg/hm^2),分析不同施氮量对两个玉米品种拔节期、大喇叭口期、吐丝期、收获期干物质的影响,基于不同时期干物质和植株氮浓度建立两个品种临界氮稀释曲线,分析不同氮利用率品种玉米临界氮稀释曲线模型的差异和氮营养指数及其与相对地上部生物量和相对产量的关系。【结果】中单909的氮利用率显著高于伟科702。在各生育时期,两个玉米品种地上部生物量随施氮量变化表现为N0 –0.341,中单909 Nc=30.801DM^–0.370)具有很好的稳定性。相比中单909的模型参数,伟科702的参数a提高了15.70%,参数b降低了7.84%,且参数a变化值大于参数b。同一时期两个品种基于此模型的氮营养指数均随施氮量的增加而上升;施氮量低于180 kg/hm^2时,随着玉米生育时期的推进,氮营养指数随施氮量的增加呈先升高再降低的趋势,当施氮量超过240 kg/hm^2时,氮营养指数一直升高。氮营养指数与相对地上部生物量、相对产量相关性均达到显著水平。【结论】本文建立的豫中地区的两个品种玉米临界氮稀释曲线模型及氮营养指数,可以很好地诊断和评价玉米植株氮素营养状况。不同氮利用率品种间临界氮浓度稀释曲线模型参数存在差异,氮高效的品种具有较低的单位生物量氮浓度和较高的曲线斜率,其各时期临界氮浓度低于氮利用率低的品种。     

Key variable for simulating critical nitrogen dilution curve of wheat: Leaf area ratio-driven approach

Nitrogen (N) dilution curves, a pivotal tool for N nutrition diagnosis, have been developed using different winter wheat (Triticum aestivum L.) tissues. However, few studies have attempted to establish critical nitrogen (N_c) dilution curves based on the leaf area ratio (LAR) to improve the monitoring accuracy of N status. In this study, three field experiments using eight N treatments and four wheat varieties were conducted in Jiangsu Province of China from 2013 to 2016. The empirical relationship of LAR with shoot biomass (expressed as dry matter) was developed under different N conditions. The results showed that LAR was a reliable index, which reduced the effects of wheat varieties and years compared with the traditional indicators. The N nutrition index (NNI) based on the LAR approach (NNI-LAR) produced equivalent results to that based on shoot biomass. Moreover, the NNI-LAR better predicted accumulated N deficit and best estimated the relative yield compared with the other two indicator-based NNI models. Therefore, the LAR-based approach improved the prediction accuracy of N_c, accumulated N deficit, and relative yield, and it would be an optimal choice to conveniently diagnose the N status of winter wheat under field conditions.     

膜下滴灌微咸水棉花临界氮稀释曲线模型与氮肥用量推荐

为了优化膜下滴灌微咸水条件下棉花生产氮素管理。于2017–2019年在新疆库尔勒市开展3 a定位施氮试验,以新陆中棉花为试验材料,设置施氮水平0（NF0）、150（NF1）、250（NF2）、300（NF3）、350（NF4）、450（NF5）kg/hm²,各试验处理灌水量均为487.5 mm,分析施氮量对棉花地上部干物质量、氮素累积吸收量、产量和氮肥利用效率的影响,构建了膜下滴灌微咸水棉花临界氮浓度稀释曲线模型。结果表明：棉花氮素累积吸收量随生育期进程的推进而增大,棉花临界氮浓度与最大地上部干物质量符合幂函数关系。氮肥农学利用率和表观利用率均与施氮量呈二次多项式变化关系,氮肥生理利用率和偏生产力均与施氮量呈线性关系。氮浓度稀释曲线模型参数a和b分别为3.967和-0.227。NF1、NF2和NF3处理的氮素营养指数均小于1,表明氮素营养供应不足,棉花生长受到氮素限制。NF4和NF5处理的氮素营养指数接近于1,说明棉花氮素营养状况较好,但NF5产量和氮素利用效率较低,NF4获得最高产量和较高的氮素利用效率。因此,350 kg/hm²为南疆膜下滴灌微咸水棉花生育期推荐施氮量,该研究构建的临界氮浓度稀释曲线模型对田间施氮管理具有重要意义。     

Mineral‐nutrient synergism and dilution responses to nitrogen fertilizer in field‐grown maize

Nitrogen (N)‐fertilizer applications to field‐grown maize may result in a dilution response whereby essential mineral‐element concentrations in shoots would decrease as shoot‐dry‐matter accumulation increased. To investigate this, the effect of N‐fertilizer treatments (no N or fertilizer rate based upon 5.3 or 8.5 t ha^–1 yield goal) on maize (Zea mays L.) shoot dry weight and shoot mineral concentrations (N, P, K, S, Mg, Ca, and Mn) at the sixth leaf (V6), twelfth leaf (V12), and tassel (VT) development stages were investigated in a 2‐year study conducted at Brookings, South Dakota (USA). With increasing N‐fertilizer application rates, shoot dry weight was greater and shoot P and K concentrations decreased. A possible explanation of this dilution response is that planting‐time P and K fertilizers, which were applied in a band near the seed furrow, may have enhanced the uptake of P and K in a manner that was independent of N‐fertilizer treatments. Increased shoot‐dry‐weight production due to the application of N fertilizers, if P and K uptake were similar across N‐fertilizer treatments, would lead to decreased shoot P and K concentrations in N‐sufficient compared with N‐deficient plants. Conversely, N‐fertilizer‐induced increases in shoot dry weight were accompanied by increased shoot concentrations of N, Ca, and Mn. This synergistic response between dry‐weight accumulation and shoot N concentration was present at all leaf developmental stages studied, while that for Ca was present only at VT. Thus, N fertilizer applications that increase shoot dry weight can affect the dilution and synergistic responses of specific mineral nutrients in maize shoots. Crop developmental stage as well as the location of these specific mineral nutrients in the soil profile might play important roles in mediating these responses.     

Determining a critical nitrogen dilution curve for sugarcane

Adequate measurements of the nitrogen (N) concentration in the aboveground biomass of sugarcane throughout the growth cycle can be obtained using the critical N dilution curve (CNDC) concept, which provides an N‐nutrition index (NNI). The aim of this work was to determine the CNDC value for Brazilian sugarcane variety SP81‐3250, establish the critical concentration of N, and determine the NNI in the aboveground biomass throughout the cane plant and first ratoon crop cycles. The study was performed in three experimental areas located in São Paulo, Brazil, during the crop cycles of 2005/2006 (18‐month cane plant) and 2006/2007 (first ratoon). The plant cane crop was fertilized with treatments of 40, 80, or 120 kg N ha^–1 and a control treatment without N. After the plant cane harvest, rates of 0, 50, 100, or 150 kg N ha^–1 were applied to the control plot and the 120 kg N ha^–1–treatment plot in a split‐plot experimental design with four repetitions. Throughout both sugarcane cycles, measurements of aboveground biomass were used to determine the dry‐mass (DM) production and N concentration for each treatment. CNDC varied between the growth cycles, with a higher N concentration observed in the initial stages of the first ratoon and a lower N dilution observed throughout the plant cane cycle. The NNI value indicated excessive N storage in the initial stages and limiting concentrations at the end of the growth cycle. CNDC and NNI allow for the identification of the N‐nutrition variation rate and the period in which the nutrient concentration limits the production of aboveground biomass. The equations for the critical N (Ncr) level obtained in this study for plant cane (Ncr = 19.0 DM^–0.369) and ratoons (Ncr = 20.3 DM^–0.469) can potentially be used as N‐nutritional diagnostic parameters for sugarcane N nutrition.     

Partitioning of biomass in water‐ and nitrogen‐stressed cotton during pre‐bloom stage

The partitioning of biomass between aboveground parts and roots, and between vegetative and reproductive plant parts plays a major role in determining the ability of cotton (Gossypium hirsutum L.) to produce a crop in a given environment. We evaluated the single and combined effects of water and N supply on the partitioning of biomass in cotton plants exposed to two N supply levels, 0 and 12 mM of N, and two water regimes, well irrigated and water‐stressed at an early reproductive stage. The N treatments began when the third true leaf was visible, while water deficit treatments were imposed over the N treatments when the plants were transferred into controlled‐environment chambers at a leaf area near 0.05 m². Both water deficits and N deficits inhibited total biomass accumulation and its partitioning in cotton. Water deficit alone and N deficit alone inhibited the growth of leaves, petioles, and branches, but did not inhibit growth of the stem and enhanced the accumulation of biomass in squares. When water deficit was superimposed on N deficit, leaf growth was inhibited, although to a lesser extent than when it was the sole stress factor, and the accumulation of biomass in squares was also inhibited. Yet, the dry weight of squares in plants exposed to water and N deficits was greater than that of non‐stressed plants. Water and N deficits, either alone or in combination, did not inhibit the growth of the tap root. Growth of lateral roots was not inhibited either by water deficit alone or in combination with N deficit, but was enhanced when plants were exposed to N deficit alone. Exposure to water deficit alone or in combination with N deficit decreased the shoot:root ratio through the inhibition of shoot growth. Exposure to N deficit alone decreased the shoot:root ratio through the combination of shoot growth inhibition and root growth enhancement.     

华北平原夏玉米临界氮稀释曲线的验证

The concept of critical N concentration （Nc） has been widely used in agronomy as the basis for diagnosis of crop N status, and allows discrimination between field situations of sub-optimal and supra-optimal N supply. A critical N dilution curve of Nc= 34.0W-0.37, where W is the aboveground biomass （Mg DM ha-1） and Nc the critical N concentration in aboveground dry matter （g kg-1 DM）, was developed for spring maize in Europe. Our objectives were to validate whether this European critical N dilution curve was appropriate for summer maize production in the North China Plain （NCP） and to develop a critical N dilution curve especially for summer maize production in this region. In total 231 data points from 16 experiments were used to test the European critical N dilution curve. These observations showed that the European critical N dilution curve was unsuitable for summer maize in the NCP, especially at the early growth stage. From the data obtained, a critical N dilution curve for summer maize in the NCP was described by the equation of Nc = 27.2W-0.27, when aboveground biomass was between 0.64 and 11.17 Mg DM ha-1. Based on this curve, more than 90% of the data for the N deficiency supply treatments had an N nutrition index （NNI） 〈 1 and 92% of the data for the N excess supply treatments had an NNI 〉 1.     

基于临界氮浓度的水稻氮素营养诊断研究

【目的】 依据水稻品种的氮素营养特征计算其氮营养指数 (NNI) 和氮素亏缺 (N_and) 值,可实现作物氮素状况的精确定量调控。本研究比较了杂交稻和常规稻在不同氮水平下的NNI和N_and值,为该诊断方法的精准使用提供依据。 【方法】 本研究选用超级杂交稻 (Y两优一号、超优千号) 和常规稻 (粤农丝苗、金农丝苗) 为对象进行田间试验。设施氮水平0、40、80、120、160、200、240 kg/hm2(分别以N0、N40、N80、N120、N160、N200、N240表示),分析测定了水稻移栽后15、30、45、60、75天和成熟期地上部干物质量及其氮浓度,构建临界氮浓度变化曲线,利用该曲线计算了不同品种在不同时期的临界氮浓度、氮营养指数和氮亏缺值。 【结果】 杂交稻地上部干物重在N0、N40、N80、N120、N160处理间差异显著,N200、N240处理间差异不显著,但显著高于其他处理;常规稻地上部干物质重在N0、N40、N80、N120处理间差异显著,N160、N200、N240处理间差异不显著,但显著高于N0、N40、N80、N120处理。水稻植株氮浓度均随着施氮水平的提高而增加,但随生育期的延长和地上部干物重的增加,水稻植株氮浓度均呈下降趋势。根据地上部干物质重与其氮浓度变化关系构建水稻临界氮浓度 (Nc) 变化曲线,杂交稻为N_c=3.36DM–0.31(R2=0.91),常规稻为N_c=2.96DM–0.25(R2=0.86)。基于临界氮浓度曲线,计算不同水稻品种的NNI和N_and,其中杂交稻和常规稻NNI变化范围分别为0.73～1.05和0.78～1.11,N_and变化范围分别为–9.8～117.8 kg/hm2和–25.4～90.3 kg/hm2。 【结论】 常规稻品种临界氮浓度高于相同生育期的杂交稻品种,但杂交稻的干物质量生产能力大于常规稻。在本试验条件下,依据N_and计算结果,杂交稻临界氮浓度下的氮素积累量大于常规稻,其中杂交稻和常规稻适宜施氮量分别为200 kg/hm2左右和160～200 kg/hm2。      

东南烟稻轮作区烤烟临界氮浓度稀释曲线的建立与验证

  【目的】  建立东南烟稻轮作区烤烟临界氮稀释曲线,探讨氮素营养指数用于诊断和评价烤烟氮营养状况的可能性,为实现烤烟合理施用氮肥提供理论依据。  【方法】  两年两地共3个田间氮肥用量试验,每个试验共设6个氮水平 (N 0、45、90、135、180 和300 kg/hm2),分析不同施氮量对移栽后不同天数烤烟地上部和叶片干物质积累量的影响。利用不同时期植株氮浓度和干物质积累量,建立地上部和叶片的临界氮浓度稀释曲线方程和干物质积累方程。结合基于无人机可见光谱平台的烤烟氮浓度无损测定方法,计算氮营养指数,判断烤烟氮营养丰缺情况。  【结果】  施用氮肥明显增加了烤烟地上部和叶片干物质积累量,不同氮肥处理间差异明显,烤烟地上部和叶片氮浓度随烤烟生长进程而降低;东南烟稻轮作区烤烟地上部及叶片的临界氮素浓度和干物质积累量符合幂指数的关系;模型进行独立验证时,氮限制组的数据均在临界氮素稀释曲线以下,而不受氮限制组的数据均在临界氮素稀释曲线附近。模型拟合的临界氮浓度和植株实际临界氮浓度呈线性相关,地上部和叶片的RMSE值分别为0.55和0.44,标准化均方根误差n-RMSE分别为25%和17%,模型具有较好的稳定性;烤烟氮素营养状况的判定可以通过应用临界氮浓度稀释曲线计算氮营养指数(NNI)实现。随着施氮水平的提高,叶片氮营养指数逐步升高,在氮施用量达到135 kg/hm2,叶片氮营养指数可在1以上,处于氮盈余状态。  【结论】  东南烟稻轮作区烤烟叶片临界氮素稀释曲线模型(N_c = 3.2339 × DM_leaves–0.475)和叶片氮营养指数能够诊断评价该区域烤烟氮营养状况,从而为优化烤烟的氮素管理提供指导。     

基于叶面积指数构建滴灌玉米营养生长期临界氮稀释曲线

明确宁夏引黄灌区基于叶面积指数(leaf area index,LAI)的滴灌玉米临界氮稀释曲线模型及其适用性,探讨以氮营养指数(nitrogen nutrition index,NNI)为监测指标对滴灌水肥一体化模式下玉米氮素营养状况诊断的可行性。该研究于2017-2018年开展了不同施氮量(0~450 kg/hm^2)下4个田块的试验,采用系统分析和统计建模的方法,分析了LAI和植株氮浓度(plant nitrogen concentration,PNC)的定量关系,构建和验证基于LAI的临界氮稀释曲线模型,并建立理论框架,将基于LAI的临界氮曲线与基于植株干物质(plant dry matter,PDM)的临界氮浓度曲线关联,比较基于LAI和PDM的临界氮曲线之间的差异。结果表明,玉米营养生长期临界氮和LAI符合幂函数关系,拟合模型的评价指标均方根误差(root mean square error,RMSE)和标准化均方根误差(normalized RMSE,n-RMSE)的结果分别为0.09和4.13%,模型具有较好的稳定性。在试验氮素水平范围内,不同生育时期NNI随施氮量的增加而增加,变化范围为0.53~1.34,NNI可以准确地反映滴灌玉米氮素营养状况。在非限氮处理下,玉米植株氮素吸收与LAI成正比,LAI与PDM的异速生长参数接近理论值2/3。构建的基于LAI的临界氮曲线可以有效地识别玉米拔节期至吐丝期植株所需的氮状态,为宁夏滴灌玉米氮肥精确管理提供了一种新的评价方法。     

平水年和欠水年渭北旱地冬小麦临界氮浓度稀释曲线构建

降雨波动大和过量施氮是限制渭北旱地冬小麦生产中氮肥高效利用和高产稳产的主要因子。该研究旨在构建2种降雨年型下冬小麦临界氮浓度稀释曲线,分析氮营养指数诊断冬小麦氮素营养状况的可行性,为考虑降雨条件下旱地冬小麦精准施氮提供理论依据。于2017—2021年在陕西合阳县开展4 a定位施氮试验,以晋麦47为试验材料,设置0、60、120、180、240 kg/hm² 5个施氮水平,其中2017—2018年和2020—2021年为平水年,2018—2019和2019—2020年为欠水年。研究2种降雨年型下施氮量对冬小麦氮素利用、产量及产量构成因素的影响,基于2种降雨年型下地上部生物量与植株氮浓度之间的关系,构建临界氮浓度稀释曲线模型和氮营养指数(nitrogen nutrition index,NNI)优化施肥方案。结果表明:1)施氮量、降雨年型及其二者互作效应对穗数、千粒质量、产量影响显著或极显著。2)2种降雨年型下冬小麦临界植株氮浓度和地上部生物量均符合幂函数关系,但模型参数之间存在差异(模型参数a在平水年和欠水年分别为3.33、2.79 g/kg,参数b在平水年和欠水年...     

作物临界氮浓度稀释模型研究述评

作物临界氮浓度是作物达到最大生长的植株最小氮浓度.临界氮浓度随地上部植株干物质积累量增加而下降,可以用幂函数模型Nc=a×Wmax-b表示.已建立了数十种作物临界氮稀释模型,根据作物收获器官的特点,分为收获籽粒、收获鲜果实、收获块根块茎和收获地上部营养体4类,不同类型临界氮浓度稀释模型在模型参数和氮素诊断应用方面各有特...     

不同水分条件下葡萄临界氮稀释曲线模型的建立及氮素营养诊断

以1a生葡萄植株“红提”为试材,在Venlo型试验温室内进行土壤水分和施氮量双因素区组试验。试验设置4个灌水水平,分别为正常灌溉量W1（田间最大持水量的70%～80%）、轻度水分胁迫W2（60%～70%）、中度水分胁迫W3（50%～60%）和重度水分胁迫W4（30%～40%）;设置4个施氮水平,分别为1.5倍推荐施氮量（N1,25.5g plant-1）、正常推荐施氮量（N2,17g plant-1）、0.5倍推荐施氮量（N3,8.5g plant-1）和不施用氮肥（N4,0g plant-1）。每10d观测一次植株体内氮浓度和植株地上部生物量,利用不同水分条件下葡萄植株在一定生长时期内所获最大生物量时对应的最小氮浓度值即临界氮浓度（Nc）构建葡萄临界氮浓度稀释曲线模型,并在此基础上建立氮素吸收模型（Nupt）和氮素营养指数模型（NNI）,对不同水分条件下葡萄氮营养状况进行定量诊断。结果表明：设施葡萄植株临界氮浓度与地上部生物量存在幂函数关系,随着灌水量的增加,葡萄植株临界氮浓度值增大,氮素吸收量及地上部生物量也呈增加趋势;在W1、W2水分条件下,葡萄植株生物量随施氮量增加而增加,而W3和W4处理葡萄生物量随施氮量增加呈先增后降的趋势;在相同水分条件下,氮浓度随施氮量增加而增加,随葡萄生长进程而降低;利用Nupt和NNI模型可对植株体内氮营养元素亏缺与否进行有效诊断。     

滴灌番茄临界氮浓度、氮素吸收和氮营养指数模拟

作物的氮浓度随生物量的增加而下降,临界氮浓度是指在一定的生长时期内获得最大生物量时的最小氮浓度值。该文在滴灌条件下,基于3a不同的氮素水平试验,构建了加工番茄地上部生物量的临界氮浓度稀释曲线模型。结果表明,临界氮浓度与地上部最大生物量之间符合幂指数关系,相关系数为R~2=0.947,加工番茄最高(%Nmax)、最低(%Nmin)临界氮浓度稀释模型亦符合幂指数关系,相关系数分别为R~2=0.959、R~2=0.925。基于临界氮浓度建立了加工番茄氮素吸收模型(Nupt)、氮素营养指数模型(NNI),可作为加工番茄氮素营养状况的判别指标,氮素吸收和氮营养指数模型对新疆北疆加工番茄种植区的适宜施氮量诊断结果一致,均以300kg/hm2为最佳施氮量。该研究所建立的临界氮浓度稀释曲线模型较前人建立的模型更具机理性,因此,该模型所得出的分析结果是合适和可靠的,并且可用于指导加工番茄动态精准施肥及为氮素优化管理的建立提供参考。     

CRITICAL NITROGEN CURVE AND NITROGEN NUTRITION INDEX FOR SPRING MAIZE IN NORTH-EAST CHINA

The study was conducted at three sites during 2008 and 2009 in the North-East China Plain (NECP). Field experiments consisted of five or six nitrogen (N) fertilization rates (0–350 kg N ha^?1). Shoot biomass and N concentration (N_c) of spring maize (Zea mays L.) were determined on six sampling dates during the growing season. Nitrogen application rate had a significant effect on aerial biomass accumulation and Nc. As expected, shoot Nc declined during the growing period. A critical N dilution curve (N_c = 36.5 W ^?0.48) was determined in China, which was a little different from those reported for maize in France and Germany. Besides, the N nutrition index (NNI) calculated from this critical N dilution curve was significantly related to relative grain yield, which can be expressed by a linear with plateau model (R² = 0.66; P < 0.001). NNI can be used as a reliable indicator of the level of N deficiency during the growing season of maize.     

Critical nitrate levels for squash,cucumber and melon plants

Abstract

Squash (Cucurbita pepo), cucumber (Cucumis sativus) and sweet melon (Cucumis dudain) plants were grown in sand culture with N as the variable and were harvested at the early flowering stage. The plants at this time showed a definite gradation of symptoms from severe to no deficiency of N. The tops were separated into leaves and stems. Leaves were separated into young, mature and old and then subdivided respectively into petioles and blades. The petioles were analyzed for NO₃‐N. The critical NO₃‐N concentration for squash, cucumber and melon on a dry basis was 1000, 2000 and 3000 ppm, respectively. A relatively high concentration of NO₃‐N in the nutrient solution decreased the growth of squash and cucumber plants significantly, but had no effect on melon plants. Melon plants can tolerate relatively high concentrations of N0,‐N in the plant tissues, while squash and cucumber cannot.     

A New Critical Nitrogen Dilution Curve for Rice Nitrogen Status Diagnosis in Northeast China

In-season diagnosis of crop nitrogen(N) status is crucial for precision N management. Critical N(N_c) dilution curve and N nutrition index(NNI) have been proposed as effective methods to diagnose N status of different crops. The N_c dilution curves have been developed for indica rice in the tropical and temperate zones and japonica rice in the subtropical-temperate zone, but they have not been evaluated for short-season japonica rice in Northeast China. The objectives of this study were to evaluate the previously developed N_c dilution curves for rice in Northeast China and to develop a more suitable N_c dilution curve in this region. A total of17 N rate experiments were conducted in Sanjiang Plain, Heilongjiang Province in Northeast China from 2008 to 2013. The results indicated that none of the two previously developed N_c dilution curves was suitable to diagnose N status of the short-season japonica rice in Northeast China. A new N_c dilution curve was developed and can be described by the equation N_c = 27.7 W~(-0.34) if W ≥ 1 Mg dry matter(DM) ha~(-1) or N_c = 27.7 g kg~(-1) DM if W 1 Mg DM ha~(-1), where W is the aboveground biomass. This new curve was lower than the previous curves. It was validated using a separate dataset, and it could discriminate non-N-limiting and N-limiting nutritional conditions. Additional studies are needed to further evaluate it for diagnosing N status of different rice cultivars in Northeast China and develop efficient non-destructive methods to estimate NNI for practical applications.     

关中平原夏玉米临界磷浓度稀释曲线构建与磷营养诊断

  【目的】  通过分析不同施磷水平下夏玉米地上部生物量与其植株磷浓度的变化关系,构建临界磷浓度稀释曲线模型,为夏玉米磷素优化管理及磷营养诊断提供理论基础。  【方法】  2019—2020年在陕西关中平原,以两个玉米品种郑单958和豫玉22为试验材料进行田间定位试验。共设4个施磷量处理 (P₂O₅):0、60、120、180 kg/hm2。在夏玉米拔节期、抽雄期、灌浆期和成熟期进行地上部取样,分析夏玉米地上部干物质量、全磷含量以及产量。利用2019年试验数据构建夏玉米临界磷浓度稀释曲线模型和磷素营养指数,利用2020年数据对模型进行验证。  【结果】  增施磷肥能显著提高夏玉米产量、地上部生物量和植株磷浓度,两个品种之间没有显著差异。随施磷水平的提高,夏玉米产量表现为先增加后减少,P120处理可获得最高产量,产量效应方程显示两年两个品种夏玉米平均理论最高产量对应的施磷量为110.2 kg/hm2。由产量构成要素看出,施磷对穗数没有显著影响,但能显著提高穗粒数和百粒重,且施磷对玉米穗粒数的影响大于对百粒重的影响。地上部生物量表现为P0c) 变化曲线:P_c = 8.11DM?0.22 (R2 = 0.886)。模型拟合的植株磷浓度和2020年玉米实际磷浓度线性相关,稀释曲线模型的RMSE和n-RMSE分别为1.146和18.23%,说明模型具有较好的稳定性。基于临界磷浓度稀释曲线计算磷营养指数 (PNI),各生育时期PNI值随磷肥用量增加而增大,随生育进程推进呈现先升高后降低趋势。PNI与相对吸磷量 (RP_upt)、相对地上部生物量 (RDW) 和相对产量 (RY) 均呈极显著相关。  【结论】  本研究建立的夏玉米临界磷浓度稀释曲线和磷营养指数 (PNI)模型能够很好地预测植株不同生育时期的磷素盈亏状况,对指导夏玉米生长季磷素营养诊断及最佳磷肥施用量具有可行性。     

Effects of nitrate‐, ammonium‐, and organic‐nitrogen‐based fertilizers on growth and yield of tomatoes

Mineral and organic fertilizers contain different forms and amounts of nitrogen (N), which can affect yield and product quality. The aim of this study was to determine appropriate amounts of N applied as nitrate (NO ), ammonium (NH ), and organic N (a mixture based on chicken manure) for optimal growth and quality of tomatoes. A pot experiment with sand as substrate was established in a greenhouse with six‐week‐old tomato plants (Lycopersicon esculentum Mill. cv. “Armada”). Nitrogen was applied in nutrient solutions at different NO : NH ratios combined with different chloride levels (NO ‐dominated, NO = NH at low Cl^–, NO = NH at high Cl^–, and NH ‐dominated, respectively) or as organic N at four N‐application rates (250, 500, 750, 1000 mg N plant^–1 week^–1). No significant differences in shoot biomass and yields of red tomatoes were observed between NO ‐ or NH ‐fed plants. Nitrogen rates above 750 mg N plant^–1 week^–1 did not significantly increase marketable fruit yield, but enhanced shoot‐biomass production. The NH ‐N‐dominated treatments (which also had high Cl^– concentrations) showed increasing incidence of blossom‐end‐rot (BER)‐infected fruits. In the organic‐N treatments, shoot‐biomass production and yields were lower than in the inorganic‐N treatments, but fruit quality was good with few BER‐infected fruits. The results show that with a total N supply below 750 mg N plant^–1 week^–1, NH can be used as equivalent N source to NO , resulting in equivalent yields of marketable fruit under the conditions in this experiment.     

Nitrogen Uptake,Leaf Nitrogen Concentration,and Growth of Saskatoons in Response to Soil Nitrogen Fertility

ABSTRACT

Nutrient requirements of the saskatoon (Amelanchier alnifolia: Rosaceae), a relatively new horticultural crop on the Canadian prairies, are unknown. In this study, two-year old saskatoon plants of the cultivar ‘Smoky’ were grown in a greenhouse in pots under four different soil nitrogen (N) regimes (20, 40, 60, and 80 mg N L^?1). Half the plants were harvested after one growing season. After a five-month period of dormancy, the remaining plants were grown for a second growing season under the same soil N regimes. At harvest, plant growth, dry weight biomass, and leaf N concentration were measured, and soil N uptake was calculated. In both years, leaf N concentration and plant N uptake were strongly positively correlated (first year r = 0.93; second year r = 0.95) and increased linearly with an increase in soil N. Stem diameter and new shoot growth increased in both years of the study in response to additional N. The soil N treatments had no significant effect on plant biomass during the first growing season. In the second year, stem, root, total shoot and total plant biomass increased with increasing soil N.