Potassium (K) is a primary limiting macronutrient for plant growth. Inappropriate K application decisions can lead to reduced yield and potassium use efficiency (KUE). Given the scarcity and non-renewable nature of K resources, developing an indicator for critical K input is essential. The apparent K balance is a simplified method calculated from fertilizer inputs and crop K uptake, enabling straightforward agronomic evaluation. Here, we hypothesize that the apparent K balance serves as a valuable indicator for determining critical K input. A twelveyear field trial with six K treatments (0, 30, 60, 90, 120, and 150 kg K ha-1 per year) was conducted to assess grain yield response to apparent K balance, establish a K input-output framework, and determine critical K input in a winter wheat-summer maize rotation system in North China. The crop yield, K uptake, and K fertilizer recovery efficiency initially increased but then declined with increasing K fertilizer rates, likely due to excessive Kinduced nutrient imbalance and salt stress. The K balance threshold can be determined based on the target yield to be pursued. A K balance of 0 -9.77 kg K ha-1 per year achieved optimal yield and maintained soil fertility. The K input-output framework provided a clear visualization of the K balance and KUE relationships. The critical K input range of 56.6 -62.5 kg K ha-1 achieved high yields with KUE improving to 85 -100 %, while sustaining high levels of soil available K and organic matter. Overall, optimizing K input within appropriate K balance thresholds enhances crop yield, KUE and soil quality simultaneously. This study provides new insights for determining critical K balance and K input, offering guidance for field-scale K management.

Phosphorus (P) is a nonrenewable resource and a critical element for plant growth that plays an important role in improving crop yield. Excessive P fertilizer application is widespread in agricultural production, which not only wastes phosphate resources but also causes P accumulation and groundwater pollution. Here, we hypothesized that the apparent P balance of a crop system could be used as an indicator for identifying the critical P input in order to obtain a high yield with high phosphorus use efficiency (PUE). A 12-year field experiment with P fertilization rates of 0, 45, 90, 135, 180, and 225 kg P2O5 ha-1 was conducted to determine the crop yield, PUE, and soil Olsen-P value response to P balance, and to optimize the P input. Annual yield stagnation occurred when the P fertilizer application exceeded a certain level, and high yield and PUE levels were achieved with annual P fertilizer application rates of 90-135 kg P2O5 ha-1. A critical P balance range of 2.15-4.45 kg P ha-1 was recommended to achieve optimum yield with minimal environmental risk. The critical P input range estimated from the P balance was 95.7-101 kg P2O5 ha-1, which improved relative yield (>90%) and PUE (90.0-94.9%). In addition, the P input-output balance helps in assessing future changes in Olsen-P values, which increased by 4.07 mg kg-1 of P for every 100 kg of P surplus. Overall, the P balance can be used as a critical indicator for P management in agriculture, providing a robust reference for limiting P excess and developing a more productive, efficient and environmentally friendly P fertilizer management strategy.

IntroductionHumic substances (HSs), components of plant biostimulants, are known to influence plant physiological processes, nutrient uptake and plant growth, thereby increasing crop yield. However, few studies have focused on the impact of HS on overall plant metabolism, and there is still debate over the connection between HS’ structural characteristics and their stimulatory actions.MethodsIn this study, two different HSs (AHA, Aojia humic acid and SHA, Shandong humic acid) screened in a previous experiment were chosen for foliar spraying, and plant samples were collected on the tenth day after spraying (62 days after germination) to investigate the effects of different HSs on photosynthesis, dry matter accumulation, carbon and nitrogen metabolism and overall metabolism in maize leaf.Results and discussionThe results showed different molecular compositions for AHA and SHA and a total of 510 small molecules with significant differences were screened using an ESI-OPLC-MS techno. AHA and SHA exerted different effects on maize growth, with the AHA inducing more effective stimulation than the SHA doing. Untargeted metabolomic analysis revealed that the phospholipid components of maize leaves treated by SHA generally increased significantly than that in the AHA and control treatments. Additionally, both HS-treated maize leaves exhibited different levels of accumulation of trans-zeatin, but SHA treatment significantly decreased the accumulation of zeatin riboside. Compared to CK treatment, AHA treatment resulted in the reorganization of four metabolic pathways: starch and sucrose metabolism, TCA cycle, stilbenes, diarylheptanes, and curcumin biosynthesis, and ABC transport, SHA treatment modified starch and sucrose metabolism and unsaturated fatty acid biosynthesis. These results demonstrate that HSs exert their function through a multifaceted mechanism of action, partially connected to their hormone-like activity but also involving hormoneindependent signaling pathways.

IntroductionMaize has a high demand for nitrogen during the growth period. The study of metabolic changes in maize can provide a theoretical basis for rational nitrogen nutrition regulation.MethodsIn order to investigate the changes of different metabolites and their metabolic pathways in maize leaves under nitrogen stress, we used ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) for metabolomic analysis of maize leaves under different nitrogen treatments at three critical growth stages (V4, V12 and R1) in a pot experiment under natural conditions.Results and discussionThe results showed that nitrogen stress significantly affected sugar metabolism and nitrogen metabolism, and affected carbon and nitrogen balance, and the effects of stress on maize leaves metabolism increased with the growth process. Metabolic pathways such as the TCA cycle and starch and sucrose metabolism were mainly affected at the seeding stage (V4). The stress response to nitrogen deficiency also showed significant upregulation of flavonoids such as luteolin and astragalin during the booting stage (V12) and anthesis-silking stage (R1). During R1 stage, the synthesis of tryptophan and phenylalanine and the degradation of lysine were significantly affected. Compared with nitrogen stress, the metabolic synthesis of key amino acids and jasmonic acid were intensified and the TCA cycle was promoted under nitrogen sufficiency conditions. This study initially revealed that the response mechanism of maize to nitrogen stress at the metabolic level.

Nitrogen (N) fertilizer application has revolutionized agricultural productivity, but excessive N fertilizer application has resulted in low N use efficiency (NUE) and high N accumulation, increasing the risk of N losses. Here, we hypothesize that the apparent N balance can be used as an indicator to identify the N input for obtaining high yield with a high NUE. Thus, a 12-year field experiment involving seven N treatments (0, 120, 240, 360, 480, 600, and 720 kg N ha-1 per year) in a typical winter wheat-summer maize rotation system in North China was conducted to investigate the response of crop yield and NUE to the N balance under different N application rates and to identify the N input-output framework. The annual yield increased in a linear-platform and NUE decreased with increasing N fertilizer application. The N balance and yield are strongly correlated to predict changes in yield, and a critical N balance of 44.4-64.9 kg N ha-1 per year was recommended for optimal yield with minimal risk of N loss. The N balance and NUE can be presented in the framework of N input-output, and the critical N input estimated from the N balance of 217-252 kg N ha-1 could obtain high productivity with high NUE (74.3-79.6 %). Overall, the apparent N balance could be used as a key indicator for optimizing N input, providing a strong reference for limiting N excess in intensive production areas and evaluating agronomic and environmental performance in N management. Data Availability: The datasets generated during and analyzed during the current study are available from the corresponding author on reasonable request.

基于叶绿素计测定的SPAD值与植物叶片叶绿素和氮浓度的关系,详细综述了用叶绿素计在玉米、小麦、水稻以及其他作物上进行氮素营养诊断的研究进展.第一,"相对SPAD值"、"氮饱和指数"或"归一化SPAD"等指标能够消除或减小品种、生育期及区域年际间的误差;第二,不同生育期应选择理想指示叶作为诊断目标;第三,不同叶位间的SPAD差值与氮素营养的关系较为稳定可靠.总结了基于SPAD的作物营养诊断和推荐施肥技术规范、不同作物种类SPAD值及其衍生参数的筛选、模型的稳定性和普适性,除氮素外其他营养元素与SPAD的响应关系等方面存在的问题和不足.在此基础上提出了利用叶绿素计开展植物氮素营养诊断与施肥需要进一步研究的方向:一是建立基于SPAD的不同作物氮素营养诊断的技术规范;二是确定基于叶片SPAD值的作物氮营养丰缺指标;三是建立基于叶片SPAD值的作物施肥模型;四是开发基于SPAD的施肥决策支持系统;五是开展钾、镁、铁、锰等与叶绿素合成有关的其他营养元素与SPAD值的关系研究.

[目的]研究冬小麦–夏玉米轮作体系下砂质潮土长期施磷的作物产量效应、磷肥利用效率、土壤有效磷农学阈值及有效磷对土壤磷素盈亏的响应关系,为农田磷素养分管理提供依据.[方法]磷肥长期定位试验自2008年起在河北廊坊进行,种植制度为冬小麦–夏玉米轮作,供试土壤为砂质潮土,设置6个施磷(P2O5)水平(0、45、90、135、180、225?kg/hm2),依次表示为P0、P45、P90、P135、P180、P225.在2020年(试验的第12年)测定作物产量、作物吸磷量、土壤有效磷含量,分析了周年产量和土壤有效磷演变特征、作物有效磷农学阈值、土壤有效磷与累积磷盈亏的关系.[结果]施磷显著提高了冬小麦–夏玉米周年产量和作物吸磷量,产量与吸磷量随施磷水平提高先升高后降低.达到最高周年产量(14627?kg/hm2)的施磷量为152?kg/hm2.以该最高产量的90％为实际生产目标,适宜施磷量为90?kg/hm2.磷肥利用率随轮作周期延长而提高,12年平均磷素表观利用率和累积利用率变幅分别为36.98％～98.10％和26.26％～71.85％.周年施磷量超过90?kg/hm2时,施磷对作物吸磷量影响不显著,且磷肥表观利用率、累积利用率显著降低.P0～P225处理表观磷盈余12年平均值分别为–11.30、–7.38、0.94、20.05、37.21、57.68?kg/hm2;至2020年累积磷盈亏分别为–144.92、–88.57、11.33、240.56、446.48、692.15?kg/hm2.砂质潮土有效磷含量随累积磷盈余量的变化呈现两段线性关系,拐点出现在土壤累积磷盈余量P?218.81?kg/hm2.低于此值时,土壤每盈余P?100?kg/hm2,有效磷含量上升0.48?mg/kg;当土壤累积磷盈余高于此值时,土壤每盈余P?100?kg/hm2,有效磷含量上升3.37?mg/kg.冬小麦、夏玉米有效磷农学阈值分别为10.20、5.93?mg/kg,施磷量为90?kg/hm2时,冬小麦、夏玉米季土壤有效磷含量最接近农学阈值.[结论]在作物秸秆还田条件下,砂质潮土冬小麦–夏玉米轮作体系周年施磷量为90?kg/hm2,可以兼顾冬小麦–夏玉米轮作周年对磷素的需求,维持土壤磷素的表观平衡,在保证产量的前提下实现磷素平衡和磷肥高效施用.砂质潮土磷的储存阈值为218.81?kg/hm2,当土壤磷累积量低于该阈值时,施磷提高土壤有效磷含量的效果较低;而当磷累积量高于该阈值时,施磷可显著提升土壤磷的有效性.

本研究以两个不同玉米品种(冀玉5817和郑单958)为研究对象,同步获取其关键功能叶片(玉米生育前期为最上部完全展开叶、吐丝后为穗位叶)氮含量和光谱反射率,分析不同施氮水平下两个品种关键功能叶片氮含量的响应特征和产量反应.研究表明,不同品种在整个生育期的叶片氮含量的变化整体趋势一致,两个玉米品种最优氮处理均为180 kg/hm2,冀玉5817氮含量在成熟期之前普遍高于郑单958,两个品种对不同氮处理响应有所差异.本研究建立基于优化处理的氮素丰缺诊断指标,即氮胁迫指数(NSI)和氮胁迫光谱指数(NSSI).基于光谱参数NVI(570,670)构建的NSSI对缺氮响应比较敏感,并且对两个品种均适用.该方法及其构建的参数通过与同条件下优化处理进行比较,避免了氮素营养的光谱诊断受品种和生育期的影响,并且光谱参数可实时、快速和无损地获取,为玉米生育期内氮肥的优化调控提供了依据.

The purpose of this study were to explore an accurate model of nitrogen accumulation factoring in temperature and light meteorological conditions from 2018 to 2019, as well as the pattern of nutrient absorption and utilization in transplanted Yongyou No. 15 rice under different conditions of nutrient application, i.e., different ratios of nitrogen, phosphorus and potassium.Using Yongyou No. 15 rice as the experimental material, five groups of samples that received different fertilization treatments and one group of samples that was not treated with fertilizer (N0P0K0) were established under field conditions for two sequential years to study the dynamic changes in rice yield and nitrogen accumulation, as well as the influence of efficiency of fertilizer used under different ratios of nitrogen, phosphorus and potassium. The principal results is that the dynamic change in nitrogen accumulation under optimal fertilization conditions could be expressed by the Gompertz model: y = 178.60 *exp(-exp[2.05-0.0884x]) (R2 =0.985, x represents the number of days after rice transplanting, and y represents nitrogen accumulation). The OPT demonstrated superiority in nitrogen accumulation in Yongyou No. 15 rice, and the days of gradual growth stage (21.78 d) and rapid growth stage (21.75 d) were all higher than those of other treatments. The Gompertz model is suitable for simulating the dynamics of nitrogen accumulation in rice under different nutrient distribution ratios In addition, the analytical method of the accurate model was used to quantitatively describe the dynamic variation of total nitrogen accumulation (TNA) in Yongyou No. 15 rice and explain the mechanism of optimal treatment (OPT) for high yields. The Gompertz model can simulate all the dynamic characteristics of the variation of nitrogen accumulation in rice plants after transplanting. The parameters i.e., N accumulation amount and the precise time to reach it, determined by the models provide a basis to accurately nitrogen regulation in the period of gradual increase and rapid increase in nutrient absorption, which is especially beneficial for the nutrient management in digital agriculture.

【Objective】This paper explored the dynamic prediction model and characteristic parameters of dry matter and nitrogen accumulation in summer maize with different nitrogen supply levels based on effective accumulated temperature, in order to provide a theoretical basis for using effective accumulated temperature to predict summer maize dry matter and nitrogen accumulation.【Method】This study was based on a two-year field experiment in Langfang, Hebei Province (2019-2020), using Zhengdan 958 as the test material, and using the normalization method to fit the dry matter and nitrogen accumulation of summer maize with different nitrogen supply levels through model screening. Based on the normalized Gompertz model of effective accumulated temperature after sowing, and using the growth rate curve and its characteristic parameters, the dry matter and nitrogen accumulation characteristics of summer maize were quantitatively analyzed.【Result】(1) Under the experimental conditions, when the amount of phosphorus and potassium fertilizer was appropriate, the maximum dry matter and nitrogen accumulation of summer maize continued to increase with the increase of nitrogen application rate. (2) The normalized Gompertz model of summer maize dry matter and nitrogen accumulation established with effective accumulated temperature as the independent variable had the good biological significance. The coefficients of determination of the equation were 0.9962-0.9988 and 0.9887-0.9922, respectively. Using the second-year data for model verification, the correlation coefficients of the simulated and measured values were 0.9933-0.9959 and 0.9830-0.9923, and the standardized root mean square errors were 6.64%-16.86% and 7.31%-12.68%, respectively. The prediction effect was good. (3) The growth rate of dry matter and nitrogen accumulation of summer maize at different nitrogen supply levels all showed a “single peak curve”, and its change was closely related to the nitrogen supply level. The performance between treatments was: under the condition of moderate fertilization, the growth rate curve had the characteristics of fast rising and falling, and the growth rate curve of weight loss treatment had the characteristics of slow rising and falling. (4) The effective accumulated temperature ranges of dry matter and nitrogen accumulation during the rapid increase period of summer maize after sowing were 709.35-1 722.54 and 482.50-1 507.61 ℃·d, respectively, and the effective accumulated temperature required for the maximum rate showed that nitrogen accumulation (995.05 ℃·d) was less than dry matter accumulation (1 215.94 ℃·d). Nitrogen supply level obviously affected the accumulation of dry matter and nitrogen in summer maize to enter the accumulation temperature required for the rapid increase period, the accumulated temperature required for the slow increase period, the accumulated temperature required for the maximum increase rate, the maximum increase rate, and the average increase rate during the rapid increase period. Compared with nitrogen fertilizer treatment, the effective accumulated temperature required for summer maize to enter each critical period was significantly reduced, and the growth rate during the critical period increased significantly.【Conclusion】The normalized Gompertz model could not only simulate and predict the dynamic changes of summer maize dry matter and nitrogen accumulation with effective accumulated temperature with different nitrogen supply levels, but also clarify the quantitative relationship between effective accumulated temperature and dry matter and nitrogen accumulation. The Gompertz model based on effective accumulated temperature could be used to predict crop growth and optimal fertilization period, and had strong application value..

[目的]探究基于有效积温的不同氮磷钾处理夏玉米株高和叶面积指数(LAI)的生长动态预测模型及其特征参数,以期为利用有效积温定量模拟夏玉米生长发育动态提供理论依据.[方法]在河北廊坊两年大田试验(2019-2020年)基础上,以郑单958为试验材料,分为氮、磷、钾3个单因素肥效试验,每个因素设4个水平,分别为不施肥、低肥、适量肥和高肥处理.采用Logistic模型拟合不同氮磷钾营养水平下夏玉米株高和叶面积指数基于有效积温的动态方程,并利用增长速率曲线及其特征参数定量分析了夏玉米生长发育特征.[结果](1)在本试验条件下,与其他处理相比,适量施肥处理(N2、P2和K2)夏玉米株高最大值均为最大.过量施用钾肥对夏玉米最大株高有显著的抑制作用.适量施肥处理夏玉米株高进入平台期所需积温为952.43-958.83℃·d.适量施肥能有效增加夏玉米叶面积指数,养分过量或过少均影响叶面积的形成.适量施肥处理夏玉米叶面积指数进入平台期所需积温为849.18-952.43℃·d.(2)各施肥处理条件下以有效积温为自变量建立的夏玉米株高和叶面积指数方程的拟合度R2分别为0.9949-0.9970和0.9840-0.9939,方程均达到极显著水平,具有生物学意义.基于有效积温的株高拟合方程得出的模拟值和实测值的相关系数(r)在0.9961-0.9983;基于有效积温的叶面积指数拟合方程的模拟值和实测值的r在0.9815-0.9981.(3)各施肥条件下,夏玉米株高和叶面积指数增长速率均表现为"单峰曲线",适量施肥处理条件下,增长速率曲线呈现上升快下降也快的特点,不施氮肥、不施磷肥和不施钾肥处理增长速率曲线呈现上升慢下降也慢的特点.(4)适量施肥处理条件下夏玉米株高进入快增期积温、进入缓增期积温和达到最大增长速率积温分别为394.17、776.63和585.40℃·d,均与NO、P0和K0处理差异显著,株高最大增长速率和快增期平均增长速率分别为0.4907和0.4302 cm·(℃·d)-1,均与NO、P0和K0处理差异不显著.(5)适量施肥处理条件下夏玉米叶面积指数进入快增期积温、进入缓增期积温和达到最大增长速率积温分别为609.69、855.08和732.38℃·d,叶面积指数最大增长速率和快增期平均增长速率分别为0.0135和0.0118℃·d.[结论]养分供应不足能够增加夏玉米株高和叶面积指数进入平台期所需有效积温.基于有效积温的Logistic模型能够很好地模拟和预测不同氮磷钾处理下夏玉米株高和叶面积指数的动态变化.适量施肥条件下方程的拟合度和稳定性优于养分过量或过少的拟合方程.不施肥处理相比适量施肥处理,夏玉米株高和LAI达到关键期所需积温(进入快增期所需积温、进入缓增期所需积温、最大增长速率所需积温)明显增加,关键期增长速率(最大增长速率、快增期平均增长速率)明显减小.本研究为有效积温定量模拟夏玉米生长发育动态提供了理论依据.

Maximizing grain yields with effective fertilization technologies and minimizing nitrogen losses is essential in agroecosystems. In this research, we conducted a two-year field experiment to explore whether dripline spacing and fertilization rate would affect maize grain yield. Two dripline spacings (i.e., one drip line per row of maize with a row space of 60 cm and one drip line per two rows of maize) and two fertilization rates (i.e., high fertilization level: N, 180 kg ha −1 ; P 2 O 5 , 90 kg ha −1 ; and K 2 O, 90 kg ha −1 and low level: N, 139.5 kg ha −1 ; P 2 O 5 , 76.5 kg ha −1 ; and K 2 O, 76.5 kg ha −1 ) were employed in this research. The results showed that maize yield was significantly affected by both dripline spacing and fertilization rate. The maize yield was 10.2% higher in the treatment with one drip line per two rows than that in the treatment with one drip line per row. Maize yield increased by 10.9% at the high fertilization level compared to that at the low fertilization level. The quantity of cumulative ammonia volatilization was reduced by 15.1% with one drip line per two rows compared to that with one drip line per row, whereas it increased by 26.9% at the high fertilization level compared with that at the low fertilization level. These results indicated that one drip line per two rows with a high fertilization rate increased the yield and could reduce the environmental burden, which may be economically beneficial and environmentally sound for maize fertigation for green agricultural development.

[目的]作物叶片颜色反映土壤养分的供应状况.研究作物叶片氮素相关的特征光谱信息与土壤无机氮含量的关系,以建立基于叶片光谱信息的土壤无机氮含量诊断模型,实现利用高光谱技术对作物和土壤进行实时监测.[方法]在两年(2017—2018)的玉米(郑单958)田间试验中,设置6个施氮水平,施氮量分别为0、60、120、180、240、300 kg/hm2.在玉米的拔节期、大喇叭口期、开花吐丝期、灌浆期测定叶片高光谱反射率,对植株和土壤样品进行采集,分析土壤无机氮含量的变化,明确叶片光谱反射率与土壤无机氮含量的关系,利用光谱参数和偏最小二乘回归法(partial least squares regression,PLSR)建立诊断模型并进行模型精度的评价.[结果]施氮处理土壤无机氮含量显著高于不施氮处理,随着生育期的推移,土壤无机氮含量呈递减趋势,追肥可显著提高土壤无机氮含量.拔节期和开花吐丝期叶片光谱反射率与土壤无机氮含量在可见光波段呈负相关关系,在近红外波段呈正相关关系;大喇叭口期两者在可见光波段呈负相关关系,灌浆期两者无明显相关关系.在光谱参数模型中,4个生育期土壤无机氮含量预测的最佳光谱指数分别为RVI-2、RSI(534,726)、RSI(567,519)和RVI-2,其回归模型验证集的R2分别为0.642、0.749、0.696、0.540.在PLSR预测模型中,利用PLSR建立的诊断模型验证集的R2分别为0.876、0.838、0.765、0.595,RPD(ratio of percent deviation)分别为2.140、2.077、2.002、1.369.[结论]基于叶片光谱反射率建立的PLSR估算模型,在玉米的拔节期、大喇叭口期、开花吐丝期均能很好地预测土壤无机氮含量.因此,利用叶片光谱特征诊断土壤无机氮含量具有一定的可行性.

[目的]研究不同层位玉米叶片氮素指标的变化,确定在不同生育时期进行营养诊断的最佳叶片,以便能够及时、准确地进行氮素营养光谱诊断,实现玉米高产和肥料高效益.[方法]设置两年(2017和2018)的盆栽试验,共设6个施氮水平,分别在玉米的关键生育时期(拔节期、大喇叭口期、开花吐丝期和灌浆期)按叶片层位取样,分析叶片生理生化指标(叶片氮含量、叶绿素含量、可溶性蛋白质含量、可溶性糖含量、叶片厚度和净光合速率)的变化及其与SPAD值的关系,确定利用SPAD值对叶片氮含量进行估算的最佳叶片.[结果]1)叶片氮含量、叶绿素含量、可溶性蛋白质含量、叶片厚度及净光合速率随着氮肥增施呈现先增加后平稳的趋势,与叶片SPAD值呈正相关关系;可溶性糖含量随着氮肥增施呈先减少后平稳的趋势,与SPAD值呈负相关关系.2)叶片氮含量、叶绿素含量、可溶性蛋白质含量、叶片厚度、净光合速率及SPAD值垂直分布上均表现为上层叶片>下层叶片;可溶性糖含量表现为下层叶片>上层叶片.3)SPAD值与叶片氮含量之间建立的线性回归模型均达极显著水平,拔节期和灌浆期的上层叶片、大喇叭口期和开花吐丝期的中层叶片氮含量与SPAD值回归决定系数(R2)较高,分别为0.768、0.865、0.893、0.924.[结论]生育期、氮水平和叶片层位显著影响玉米叶片中与氮素营养相关的生理生化指标,呈现一定的空间异质性,在玉米拔节期和灌浆期利用SPAD值进行叶片氮含量营养诊断时应考虑测定上层叶片(顶两片、三片完全展开叶),而在大喇叭口期和开花吐丝期应测定中层叶片(中两片完全展开叶、穗位叶及以下两片叶).

从食物链营养的角度提出植物健康营养理论,即在不影响植物正常生长发育的条件下,通过调节供给植物的营养元素而生产出符合特定需求的产品,提高植物栽培的功能性和经济价值.我们把这种同时注重植物营养和产品功能的人工栽培植物的营养理论称为植物健康营养理论,这里将不具备植物营养功能,但对整个食物链特别是对人和饲养动物有营养作用的元素称为健康元素.根据矿质元素的作用对象,可将健康元素分为营养健康元素和非营养健康元素两类.营养健康元素是指它本身是植物必需营养元素,同时又对食物链上端生物也有重要健康作用.非营养健康元素是指其对植物本身的生长发育没有营养作用,仅对食物链上端的生物有健康作用.把通过植物吸收矿质元素的方式以达到食物链促进健康的栽培管理方式称为健康栽培.本文还定义了植物健康营养理论的学科边界,指出:"奢侈吸收"与动物健康的关系研究,健康元素在植物体内的代谢,健康元素在食物链中的传递形式,植物体内健康元素的含量阈值,健康元素的高效施用与管理都是植物健康营养理论的研究范畴.

自化学肥料出现以来,极大地保证了世界的粮食安全.由于化学肥料可使粮食单产大幅提高,从而节省了大量的农田,使得不适宜农耕的土地大量被用于生态建设.所以,化学肥料在一定程度上保证了生态环境的健康发展.化学肥料的大量使用也会带来一定的负面作用,如水体富营养化等生态健康问题,然而解决这些问题的措施是合理施用化学肥料,而不是拒绝使用化学肥料.现代农业离不开化学肥料,生态健康也离不开化学肥料.

本文分析了近200年来,国际上植物营养研究特别是有关植物营养理论研究的发展过程,从早期对植物营养的研究开始,论述了腐殖质营养理论的形成与发展以及腐殖质营养理论的具体内容;论述了植物营养矿物质理论的发现过程及李比希否定腐殖质营养理论的理由与事实;介绍了李比希对矿质营养理论的论述与完善过程,分析了矿质营养理论早期的争议及争议的原因;评价了矿质营养理论对农业的贡献.本文还针对目前出现的有机营养理论及碳营养进行质疑,指出了小分子有机物质对植物生长发育的作用.

[目的]探明 γ-聚谷氨酸(γ-PGA)促进夏玉米生长和养分吸收利用的调控机制,为其在玉米生产中的科学使用提供技术指导和理论依据.[方法]以玉米品种郑单958为试材,于2017和2018年在河北廊坊进行了田间试验.在两个氮肥水平下,即常规用量(N 180 kg/hm2)和减量30％(N 126 kg/hm2),分别喷施 γ-PGA或谷氨酸两种增效剂(剂量分别为0、37.5、150 g/hm2),共10个处理.在玉米5个关键生育期采集植株样品,测定植株干物质积累和氮磷钾养分含量,并于收获期测定了玉米籽粒产量.[结果]1)两种增效剂处理的夏玉米穗粒数、产量、干物质和养分积累量存在显著差异,喷施 γ-PGA效果显著优于喷施谷氨酸.与清水对照相比,喷施γ-PGA可通过提高穗粒数来实现增产,干物质积累总量显著增加,且主要促进开花前后的干物质积累,氮磷钾积累总量也有显著增加,两个剂量间无明显差异.喷施谷氨酸与清水对照的效果无明显差异.2)常规施氮水平下,与清水对照相比,喷施低量 γ-PGA干物质积累总量显著增加5.08％,但增产作用不明显;而喷施高量 γ-PGA的处理虽然干物质积累总量增加不明显,但穗粒数明显增加,产量显著增加3.42％,两剂量处理氮磷钾积累量均显著增加,增幅分别为5.20％～6.97％、7.29％～10.85％、3.48％～5.27％;减氮30％ 水平下,喷施高量 γ-PGA处理穗粒数提高,产量显著增加3.07％,而低量处理的穗粒数和百粒重均有明显提高,并显著增产,两剂量下干物质和钾积累总量分别显著增加6.48％～7.93％、4.36％～6.12％,而低量处理氮磷积累量分别显著增加8.41％、11.94％,显著高于高量处理.两种施氮水平下,谷氨酸处理各指标与对照均无明显差异.3)高产年份(2017年),喷施高量 γ-PGA显著增产2.54％,低量处理增产不明显,两个喷施剂量均显著增加干物质和氮磷钾积累总量;低产年份(2018年),两个剂量 γ-PGA处理的产量均显著增加,增幅分别达4.37％、4.14％,低量处理均显著增加干物质和养分积累量,且显著高于高量处理.对谷氨酸处理而言,仅在2018年低量处理通过增加百粒重使得产量显著增加,但效果低于 γ-PGA处理.[结论]喷施 γ-PGA促进夏玉米开花前后干物质积累,提高干物质和养分积累总量,增加穗粒数提高产量,而喷施谷氨酸无明显效果.可见,γ-PGA的增产增效并非主要是由于分解的谷氨酸起作用.减氮30％ 水平下喷施 γ-PGA的增产增效作用大于常规施氮,且常规施氮水平下喷施高量 γ-PGA的增产效果更好,而减氮30％ 水平下喷施低量 γ-PGA的效果更好,表现为喷施低量 γ-PGA处理>常规施氮对照>减氮30％ 对照,说明减氮30％ 下喷施低量 γ-PGA能达到减肥增效的目的.

[目的]通过研究华北地区中低产土壤条件下不同氮、磷、钾肥施用量在滴灌夏玉米上的肥料效应,从而优化滴灌施肥系统,为夏玉米高效滴灌施肥提供理论依据,推进水肥一体化技术.[方法]通过两年田间试验,以郑单958为供试品种,滴灌带设置为一管带两行,氮磷钾分别设4个处理,其中氮肥处理为0、144、1 80、216kg·hm-2(记为N0、N1、N2、N3),磷肥处理为0、72、90、108 kg·hm-2(记为P0、P1、P2、P3),钾肥处理为0、72、90、108 kg·hm-2(记为K0、K1、K2、K3),氮磷钾肥料分4次滴施,以研究不同处理对夏玉米产量及不同生育时期干物质积累的影响,分析不同处理下肥料的利用率.[结果](1)华北地区中低产田条件下夏玉米产量随施氮磷肥的用量呈抛物线性变化,当施氮量为180 kg·hm-2,施磷量为90 kg·hm-2时,作物产量最高;当氮磷肥施用量超过最高产量施肥量时,作物产量随施氮磷用量的提高呈下降趋势,但氮肥处理的下降程度差异不显著,而磷肥施用量超过90 kg·hm-2时,作物产量随施磷量的提高显著下降(P＜0.05);在本处理中,夏玉米产量随施钾量的提高,均呈增加趋势.(2)不同施肥处理对夏玉米生育前期干物质积累几乎没有影响,在灌浆期与收获期时干物质积累与施氮量、施磷量均呈抛物线性变化,变化趋势与产量基本相同.(3)不同处理的氮磷钾肥利用率不同,分别为33.39％-58.44％、14.15％-28.88％、54.70％-65.75％,当夏玉米产量最高时的氮、磷、钾肥利用率两年平均为51.21％、28.88％、65.75％;在最高产量条件下,氮、磷、钾肥的平均农学效率分别为8.08、11.41和8.83 kg·kg-1;偏生产力分别为59.88、119.75和100.65 kg·kg-1.[结论]在华北地区中低产土壤滴灌施肥条件下,最适宜的氮磷施用量分别为180 kg·hm-2和90 kg·hm-2,当施氮量超过180 kg·hm-2、施磷量超过90 kg·hm-2时,夏玉米产量会出现下降,但随施钾量的提高,产量有增加的趋势.滴灌施肥可获得较高的氮磷钾肥利用率,分别为51.21％和28.88％和65.75％.

In order to clarify the location of nitrogen nutrient diagnosis of maize leaves at different growth stages, and to establish an accurate and robust model to diagnose maize's nitrogen nutrition, which aims to guide rational fertilization and improve recovery rate, in this experiment, a single factor pot experiment was designed, and maize (Zhengdan 958) was used as the research object to study the distribution and variation of nitrogen content in different layers of leaf under different nitrogen nutrition levels. The distribution and variation of N content and the spectral response characteristics of maize leaves were analyzed. And the correlation relationship between nitrogen content and spectral reflectance of different layers leaves at different growth stages was investigated. Moreover, the regression relationship between the leaf nitrogen content and the ratio spectral index (RSI) which was composed of any two bands between 400 similar to 2 000 nm was explored. According to these analyses, leaf layer, optimal RSI and estimation models were initially determined at different stages for nitrogen nutrition diagnosis by spectral technique. The main results are as follows: The results indicate that the maize's nitrogen content in different layers is as follows: the upper layer>the middle layer>the lower layer; and that as the stages of growth forward, leaves' nitrogen content in upper layer, under the condition of low-nitrogen, appears to first decrease and then increase (after manuring) and decrease again while keeping the tendency of decrease under the condition of high-nitrogen, with the leaves' nitrogen content in the levels of middle and low appearing to decrease. At the Six-leaf stage, the lower layer of leaves has a larger sensitivity range and a stronger correlation coefficient. At Nine-leaf and Filling stage, spectral reflectance of the upper layer maize leaves was more sensitive and correlated. At the flowering and silking stage, spectral reflectance of the middle layer leaves was more sensitive and relevant. SO the lower leaves were selected as the diagnosis target at the Six-leaf stage, and the optimal ratio spectral index RSI (1 811, 1 842) was selected to establish the linear estimation model. The upper leaves were selected as the diagnostic target at the Nine leaf stage and the Filling stage, and the optimal ratio spectral indices were RSI (720, 557), RSI (600, 511) to establish the linear estimation model, respectively. The middle leaves were selected as the diagnostic target during the anthesis-silking stage, and the RSI (688, 644) spectral index was selected to establish the estimation model. The research results could provide a theoretical basis for rapid and accurate nitrogen nutrition spectrum diagnosis method in maize or other crop.