Overlooked contribution of the biological pump to the Pacific Arctic nitrogen deficit

The nutrient-rich Pacific Ocean seawater that flows through the Bering Strait into the Chukchi Sea is generally considered to be the most important source of nutrients to the Arctic euphotic zone.The inflow is characterized by nitrogen deficit and low nitrate/phosphate(N/P)ratios;this is ascribed to sedimentary denitrification on the Chukchi shelf by preoccupant opinions.However,the Chukchi Sea also has high primary production,which raises the question of whether the biological pump may also significantly modulate nutrient properties of the throughflow.Here,we show that nitrate concentrations of the Pacific inflow gradually decrease northward in association with notable biological utilization.The phytoplankton N/P uptake ratio was 8.8±2.27,higher than the N/P ratio of Pacific inflow water(5-6).This uptake ratio,in combination with efficient vertical nitrogen export,serves to preferentially remove nitrogen(relative to phosphorus)from upper waters,thereby further intensifying the Arctic nitrogen deficit.Accordingly,as large as about 111.7×10^(9)mol N yr^(−1)of nitrate was extra consumed,according to the real N/P uptake ratio rather than the ratio of the Pacific inflow,which may be as great as half the nitrogen loss ascribed to sedimentary denitrification.Our findings suggest that besides sedimentary denitrification,biological disproportionate utilization of nutrients in the Chukchi Sea upper water is another important contributor to the nitrogen limitation and excess phosphorus in the upper Arctic Ocean.In the rapid Arctic change era,the predicted reinforced biological carbon pump could further impact the nutrient dynamics and biogeochemical process of the Arctic Ocean.

Effect of Deficit Irrigation Practice on Nitrogen Mineralization and Nitrate Nitrogen Leaching under Semi-Arid Conditions

Agricultural sector acts as a major consumer of water which accounts for 70 percent of global freshwater use. Water scarcity acts as an imminent threat to agriculture, there is a need to use those irrigation and management practices that could overcome this overwhelming situation of water scarcity. Lab incubation study was designed to evaluate the effect of different moisture levels (50%, 60%, 70%, 80%, 90%, and 100% FC) on nitrogen mineralization rate. Net nitrogen mineralization was shown at 60% and 80% FC levels. Two optimized irrigation levels (I0.6 and I0.8) along with four levels of dairy manure (10, 15, 20, and 25 Mg ha-1) were used in a lysimetric trial. Nitrate-nitrogen was measured at four depths (D1: 30 cm, D2: 60 cm, D3: 90 cm, and D4: 120 cm). Results showed strong interaction of irrigation and dairy manure at all depths. Mean maximum nitrate-nitrogen concentration was shown under full irrigation at 120 cm soil depth with the application of DM ®25 Mg ha-1. Under two levels of deficit irrigation, I0.8 has shown maximum nitrate-nitrogen concentration at 90 cm soil depth with the application of DM25, however, deficit irrigation level I0.6 restricted nitrate-nitrogen movement up to 60 cm soil depth, and high concentration was found at 30 cm soil depth. We concluded that deficit irrigation practice along with dairy manure resulted in more nitrate-nitrogen in the upper 60 cm layer of soil where it can be more available for the crops.

Physiological Mechanism of Nitrogen Mediating Cotton (<i>Gossypium hirsutum</i>L.) Seedlings Growth under Water-Stress Conditions

The objective of this investigation was to study the effects of nitrogen on tolerance to water-stress in cotton (Gossypium hirsutum L.) seedlings. Growth chamber studies with pots of washed sand were carried out in Fayetteville, USA, and Nanjing, Chinawith three water conditions (well-watered, drought-stressed, and waterlogging), and three nitrogen rates, low nitrogen (16 mM, approximately 224 mg N·l–1 water), medium nitrogen (24 mM, approximately 448 mg N·l–1 water) and high nitrogen (32 mM, approximately 672 mg N·l–1 water), respectively. The results showed that water-stress treatments reduced plant biomass, C/N ratio, root vigor and leaf photosynthesis (Pn). The plant response to water-stress resistance was affected by nitrogen, and was correlated with the activities of antioxidant enzymes. The changes of anti-oxidant enzymes was the highest in the low nitrogen rate in the drought-stressed and waterlogged cotton seedlings. Malondialdehyde (MDA) content increased significantly in the water-stress treatments, and was the lowest in the low nitrogen rate. There was a significant reduction of N accumulation under water stress. Low-nitrogen treatmentincreased C accumulation, while high-nitrogen treatment decreased N accumulation. Root vigor was decreased by water stress, and was highest in the low-nitrogen rate. After terminating the water stress, N application promoted root vigor, especially in waterlogged seedlings. The trends of Pn weresimilarto that of root vigor. These results suggested that low N application may contribute to cotton drought tolerance by enhancing the activity of antioxidant enzymes and conse-quently decreasing lipid peroxidation, and enhancing root vigor. However, higher N should be applied to waterlog- ging-stressed cotton seedlings after terminating waterlogging.

Quantification of Radiation Use Efficiency and Yield of Wheat as Influenced by Different Levels of Nitrogen and Water Stress under Semi-Arid Conditions of Faisalabad

Crop production is greatly influenced by water and nutrition stress in semi-arid areas. Nitrogen and water are two most important yield limiting factors which effect economic production of wheat. Drought initiates when large area of land suffers from absence of precipitation for temporary periods. Though, not only water scarceness but also low relative humidity and high temperature are other climate factors which induce drought condition. Whereas Effective nutrition (nitrogen) maintains crops metabolic activities and has the potential to lessen drought stress. According to study carried out to explore the influence of varying levels of potential soil moisture deficit (PSMD) and nitrogen, an experiment was planned at agronomy research area, University of Agriculture, Faisalabad. It was laid out in randomized complete block design (RCBD) with split plot arrangement, and replicated thrice. Two factors: potential soil moisture deficit levels (I1: irrigation at 50 mm PSMD, I2: irrigation at 75 mm PSMD and I3: irrigation at 100 mm PSMD) were randomized in main plots, while sub plot nitrogen levels {control (No nitrogen), 50, 100 and 150 kg N ha-1} were randomized. Adequate nitrogen application along with sufficient irrigation management gave highest yield. Under water deficit conditions adequate nitrogen application ameliorates the drought stress. Highest plant height (86.27 cm), number of productive tillers (320.0), grain·spike-1(49.73), test weight (50.55 g) and grain yield (6.72 t·ha-1) were observed with 75 mm PSMD and 150 kg·ha-1 application of nitrogen. While radiation use efficiency for dry matter accumulation of wheat ranged from 1.53 - 1.87 g·MJ-1 whereas, radiation use efficiency for grain yield ranged from 0.421 - 0.473 g·MJ-1. Results revealed that highest RUE obtained I3 (75 mm PSMD) and nitrogen application at 150 kg·ha-1. Judicial application of irrigation and fertilizer not only boosts the yield but also saves resource and increases former output.

Yield and Water Productivity of Drip-Irrigated Potato under Different Nitrogen Levels and Irrigation Regime with Saline Water in Arid Tunisia

Field studies were conducted on a sandy soil during autumn of 2010 and 2011 in an arid region of Tunisia to investigate the effects of nitrogen and irrigation regimes with saline water on yield and water productivity (WP) of potato (Solanum tuberosum L. cv. Spunta) and soil salinity. For the two years, irrigation treatments consisted in water replacements of cumulated crop evapotranspiration (ETc) at levels of 100% (I100, full irrigation), 60% (I60) and 30% (I30), when the readily available water in I100 treatment was depleted, while the nitrogen treatments (N) were 0, 100, 200, and 300 kg/ha (No, N100, N200, and N300). Results showed that soil salinity values remained lower than those of electrical conductivity of irrigation water (ECiw) and were the lowest under treatment I100 and the highest with I30 treatment. Relatively low ECe values were also observed under I60 treatment. The highest potato yields for the two years were obtained with I100 treatment. Compared to I100, significant reductions in potato yields were observed under I60 and I30 deficit irrigation treatments resulting from a reduction in tubers number/m2 and tuber weight. The water productivity (WP) was found to significantly vary among treatments, where the highest and the lowest values were observed for I30 and I100 treatments, respectively. Potato yield and WP increased with an increase in nitrogen rates. The rate of 300 kg N/ha was seen to give good yield and higher WP of potato under full (I100) and deficit (I60) irrigation treatments. However, application of N adversely affected potato yield and WP, when N level applied above 200 kg N/ha at I30. The WP was improved by N supply, but its effect decreased as the irrigation level increased. The IWP at I100, which produced the highest potato yield, was 8.5 and 9.9 kg/m3 with N300 but this increased to 11.9 and 15.6 kg/m3 at I30 with N200, in 2010 and 2011, respectively. These results suggested that potato in arid region could be cultivated with acceptable yields while saving irrigation water and reducing nitrogen supply but it was essential to exploit the interaction effect between these two parameters to maximize resource use efficiency.

Modeling the Effect of Planting Dates and Nitrogen Application Rates on Potatoes Water Productivity in Jordan Valley

Agricultural sector in Jordan is facing serious challenges in meeting the growing needs of food security because of its low water availability. Maintaining and enhancing agricultural water productivity under such prevailing environmental constraints are hard to achieve. Potatoes water productively in Jordan Valley was modeled using Decision Support System for Agrotechnology Transfer (DSSAT) under six nitrogen applications (0, 60, 80, 100, 120 and 140 kg/ha) and twelve planting dates every two weeks from October 1 to March 15 scenarios. The potatoes yield increased from 0% to 100% nitrogen treatment and then no considerable increase occurred. The potatoes’ crop yield increased from October 1st to January 15 and then decreased after which until the last day of planting date. The seasonal cumulative crop evapotranspiration for potatoes about doubled from 0% to 60% nitrogen treatment and then kept increasing gradually until the last treatment. The growing season cumulative crop evapotranspiration for potatoes increased gradually from October 1 to March 1. The water productivity increased from 0% nitrogen treatment to 100% and then decreased. The potatoes’ water productivity increased from October 1 until November 15 and then decreased to the end. From these results, we recommend that 100% of nitrogen requirements should be applied. The best window for potatoes’ planting date is the last two weeks in November.

水氮胁迫对春小麦产量与水分利用效率的影响

针对干旱地区水资源有限、小麦生产水肥投入过高和水分利用效率低的问题,探讨水氮亏缺对小麦水分利用效率的影响,为建立小麦水分高效利用理论提供一定的依据。2022年在甘肃省武威市设置试验,选定永良4号(YL4)和陇春41号(LC41)两个品种的春小麦作为研究对象,每个品种设置4个处理,包括两个水分处理即充分灌溉W_(1)处理(预测作物需水量)和调亏灌溉W_(2)处理(在拔节-孕穗期和灌浆-成熟期灌溉预测作物需水量的65%,其余生育期灌溉量为充分灌溉处理预测作物需水量的100%),两个氮肥处理即N_(1)处理(当地传统施氮量,220 kg/hm^(2))和N_(2)处理(减量施氮,110 kg/hm^(2)),重点研究节水减氮对于小麦耗水特性、水分利用效率的影响。研究结果表明,春小麦耗水量因水分亏缺和氮素亏缺而显著降低,减量施氮对耗水量的影响不显著,但降低了籽粒产量和水分利用效率。春小麦的水分利用效率受产量和耗水量调控且相关性呈抛物线关系,因此在干旱灌区可通过一定的水氮调控保持产量的同时提高水分利用效率。

亏缺灌溉对新疆不同品种春小麦产量和氮素利用的影响

【目的】在水肥一体化条件下,研究不同生育期不同亏缺灌溉水平对春小麦产量和氮素利用的影响,为优化新疆春小麦水肥管理、提高小麦生产水肥效益提供技术支撑。【方法】于2022、2023年在石河子大学农学院实验站进行了管栽试验和小区试验,灌溉方式为滴灌。采用裂区设计,主区为干旱敏感品种新春22号(XC22)和耐旱品种新春6号(XC6);副区为灌溉处理,设置全生育期充分灌溉对照[CK,土壤湿度为田间持水量(FC)的75%~80%];分蘖期轻度亏缺(T1,60%~65%FC)、中度亏缺(T2,45%~50%FC);拔节期轻度亏缺(J1,60%~65%FC)、中度亏缺(J2,45%~50%FC)5个处理。调查了开花前后春小麦茎鞘、叶、穗及籽粒干物重、氮素含量,及成熟期小麦产量和产量构成因素;计算了花前氮素积累与转运、花后氮素吸收量及氮素利用率。【结果】两品种小麦成熟期植株氮素积累量(166.15~238.87 kg/hm^(2))、成熟期营养器官氮素分配率、各器官花前氮素转运量(21.76~57.66 kg/hm^(2))及其贡献率(14.15%~31.66%)、植株花前氮素转运量(78.67~147.66kg/hm^(2))及贡献率(51.58%~81.11%)均表现为T2、J2处理低于T1、J1,而T2、J2处理下籽粒氮素分配率、植株花后氮素吸收量及贡献率则高于T1、J1。亏缺灌溉处理下,品种XC6各器官氮素积累与分配、各器官花前氮素转运量及贡献率、产量及产量构成因素总体上高于干旱敏感品种XC22。与CK处理相比,T1处理下耐旱品种(XC6)成熟期植株氮素积累量显著提高了9.98%,茎鞘花前氮素转运量及贡献率分别提高了24.06%、18.91%,植株花前氮素转运量及贡献率分别显著提高了19.21%、12.53%,产量显著提高了12.17%,氮素利用率提高了2.25%,氮肥生产效率显著提高了12.16%,氮素收获指数提高了3.71%。而干旱敏感品种XC22的各项指标在4个亏缺灌溉处理下均低于CK。【结论】在新疆灌溉绿洲农业区,分蘖期轻度亏缺灌溉(60%~65%FC)可显著提高耐旱型春小麦花前氮素的积累量和向籽粒的转运,提高氮素利用率和氮素收获指数,并有效提高产量,进而达到节水高产的效果;而干旱敏感型品种不适宜于任何时期的亏缺灌溉。

施氮对亏缺灌溉措施下棉花生长、养分吸收及产量的影响

研究节水灌溉措施结合氮肥管理对棉花干物质积累、生理响应、养分吸收和产量的影响,为干旱区棉花增产和水肥高效利用的农艺实践提供理论依据。以棉花‘新陆早72’为试验材料,研究了在2种灌溉处理下(正常灌溉,W1;亏缺灌溉,W2)不同施氮量(210 kg·hm^(-2),N1;300 kg·hm^(-2),N2;390 kg·hm^(-2),N3)对棉花干物质积累、光合生理特性、养分吸收、抗氧化防御、渗透调节及产量的影响。结果表明:与正常灌溉相比,亏缺灌溉通过降低干物质积累、净光合速率、抗氧化酶活性以及养分吸收降低了籽棉产量。与亏缺灌溉下进行适量施氮相比(W2N2),增加施氮量处理(W2N3)的净光合速率和叶面积指数分别提高12.5%和10.9%,抗氧化酶活性、渗透调节物质分别提高13.6%、42.6%,这些过程减轻了亏缺灌溉对棉花生长造成的伤害,促进养分吸收和干物质积累,最终籽棉产量提高5.6%。此外,与正常水肥管理处理(W1N2)相比,亏缺灌溉后增加施氮量(W2N3)并没有降低籽棉产量,反而通过改善冠层光合能力、抗氧化防御及渗透调节能力延长了干物质持续积累时间,使植株提前3~4 d结束生育进程。综上所述,在干旱区开展棉花节水灌溉措施时,建议在常规施氮量的基础上再增加30%,该施氮量可以在保证棉花不减产的同时节约更多的灌溉水,并且该措施对干旱区滴灌棉花生产中的节水增效和可持续生产具有重要意义。

持绿型小麦冠温特性及其对低氮和高温的适应性

【目的】研究持绿型小麦的冠温特性及其对高温和低氮的适应性,为小麦低温种质资源鉴选提供依据。【方法】以正常栽培条件为对照,对低氮和高温处理下冬小麦旗叶净光合速率、叶绿素荧光参数、茎鞘干物质量、产量、绿叶面积和冠层温度等进行测定。【结果】在不同生长条件下,持绿型小麦豫麦66和潍麦8均表现出较低的冠层温度和较高的绿叶面积。持绿型小麦旗叶的净光合速率及光化学淬灭系数都高于非持绿型小麦,非光化学猝灭系数低于非持绿型小麦,叶片吸收的光能较多地用于光化学反应,而以热能的形式辐射出来的较少。低氮和高温逆境下持绿型小麦茎鞘干物质转运率增加,收获指数提高,经济产量高。【结论】持绿型小麦冠层温度低,叶片衰老延迟,干物质累积多,具有良好的增产潜力,在低氮和高温逆境下更有优势,可用于筛选低温种质资源和创建具有更好生物学性状、高产的优良品种。

水肥亏缺下水稻叶片气孔导度与光合速率耦合模型

叶片气孔导度-光合速率的耦合模型是作物生理模拟的关键,是估算作物生长及水分利用动态的基础.采用盆栽试验实测资料,建立Leuning-Ball气孔导度模型及其耦合模型,考虑水肥因子对气孔导度、光合速率的影响,引入水稻叶片叶气温差、叶绿素相对含量修正气孔导度模型,并进行比较.结果表明,考虑叶气温差、叶绿素相对含量的气孔导度-光合速率耦合模型具有针对水肥限制条件下更高的模拟验证解释能力,针对气孔导度,最大相对误差由125.5%、128.8%分别降至98.2%和126.6%,针对光合速率,平均相对误差由32.3%、74.3%降至20.5%和39.3%,最大相对误差则由331.5%、327.9%降至177.1%和113.4%.

不同生育期水分亏缺及氮营养对冬小麦生长和产量的影响

利用管栽条件研究了不同施氮量条件下不同生育阶段水分有限亏缺对冬小麦生长及其产量的影响。结果表明:在冬小麦拔节期、开花期、灌浆期水分亏缺处理,其株高、根、冠干物质及植株总重差异达到极显著水平,无论任何生育阶段水分亏缺还是全生育期正常供水,株高、根、冠及植株总重都随施氮量的增加而增加,并且氮肥对地上部的促进作用要大于对地下部的促进作用。在拔节期、开花期水分亏缺对小麦的每穗粒数、千粒重、单株产量影响显著,灌浆期水分亏缺对千粒重有显著影响。在适中的施氮水平下苗期、灌浆期适当的水分亏缺对冬小麦的生长和产量没有显著的影响,而在高氮、低氮条件下影响较为显著。

玉米叶绿素、脯氛酸、根系活力对调亏灌溉和氮肥处理的响应

通过玉米盆栽试验,研究了调亏时期、施氮量和灌水水平对玉米生理指标的影响。结果表明,不同生育阶段的水分亏缺和施氮量对叶绿素、脯氨酸、根系活力影响显著。水分亏缺导致了叶绿素含量降低,施氮量和叶绿素含量呈正相关。叶绿素在拔节后期达到最大值,抽穗期开始降低。调亏灌溉会使玉米叶片脯氨酸含量增加,苗期增加较小,抽穗期达到最大。施氮会调亏灌溉的脯氨酸含量略有减少。持续干旱导致在抽穗期的脯氨酸含量增长受到限制。玉米根系活力随着生育时期进程先增后减。在水分亏缺条件下,根系活力降低,覆水后根系活力补偿效应明显;在相同水分条件下,施氮处理的根系活力较大。最佳的水氮组合为苗期亏水高氮处理。

基于无人机高光谱遥感的水稻氮营养诊断方法

氮亏缺量能够直接反映作物氮营养缺失程度,快速、大面积获取水稻氮亏缺量信息对实现水稻精准施肥具有重要意义。而现有的研究大都集中于利用无人机遥感监测水稻氮营养情况,对氮亏缺量本身的研究较少。本研究基于无人机高光谱遥感获取冠层光谱数据、通过田间采样获取水稻农学数据,研究东北地区水稻临界氮浓度曲线构建方法,在此基础上确定水稻氮亏缺量;以氮亏缺量约等于0状态下光谱为标准光谱,分别对光谱反射率进行比值、差值、归一化差值变换,通过竞争性自适应重加权采样法对原始光谱反射率与变换后光谱反射率进行特征波长提取,并以二者提取的特征波长为输入变量,氮亏缺量为输出变量,分别构建基于多元线性回归、极限学习机与蝙蝠算法优化极限学习机3种算法的水稻氮亏缺量反演模型。结果表明:基于田间数据构建东北地区水稻临界氮浓度曲线方程系数a、b分别为2.026与-0.460 3,和以往研究基本一致;相比其余变换方法,对水稻冠层光谱进行归一化差值变换与特征波长提取显著提高了冠层光谱反射率与水稻氮亏缺量的相关性,也提高了后续反演模型的反演结果;以归一化差值光谱为输入的蝙蝠算法优化极限学习机反演模型预测效果显著优于其余模型,验证集R^(2)为0.830 6,RMSE为0.814 1 kg/hm^(2),具有较好的氮亏缺量估测效果。

水氮耦合对干热区小粒咖啡产量和品质的影响

为探明干热区小粒咖啡优质高产的水肥管理模式,通过连续2 a大田试验研究旱季4个灌水水平（充分灌水W1和亏缺灌水W2、W3、W4,W2、W3和W4灌水量分别为W1的80%、60%和40%）和3个施氮水平（N1：140 g/棵、N2：100 g/棵和N3：60 g/棵,纯氮量）对小粒咖啡产量、品质及水分利用效率的影响,并通过主成分分析对综合营养品质进行评价。结果表明,与W4相比,提高灌水量可增加干豆产量42.8%~151.0%、生豆中绿原酸含量16.9%~31.5%,水分利用效率随灌水量的提高先增后减,W2的水分利用效率最大。与N3相比,提高施氮量增加干豆产量、水分利用效率、生豆中蛋白质和绿原酸含量分别为32.9%~42.6%、32.0%~45.8%、5.9%~9.7%和7.0%~12.6%,N2的干豆产量和水分利用效率最大。与W4N3相比,提高水氮用量能同时增加干豆产量和水分利用效率,分别增加22.0%~307.5%和18.2%~205.3%。W1N2处理获得2 a的最大均产,为5 587.42 kg/hm2。主成分分析结果表明,W2N2的综合营养品质最优,而水氮不协调会导致品质下降。与W4N3相比,W2N2显著提高干豆产量、水分利用效率和生豆中蛋白质和绿原酸含量,降低粗纤维含量。因此,从优质高产角度考虑,干热区小粒咖啡的水氮耦合模式为W2N2组合。

不同生育期水分亏缺灌溉和氮营养对玉米生长的影响

通过玉米盆栽试验,设置了全生育期土壤充分灌水、苗期亏水、拔节期亏水、灌浆期亏水、成熟期亏水5个水分处理和施氮量分别为0、0.1、0.30、.5 g/kg的4个施氮水平,依次以N0、N1、N2、N3表示。研究了不同生育期水分亏缺和氮营养对夏玉米生长的影响。结果表明:在不同施氮条件下,不同生育期亏水均对玉米的生长产生不同程度的抑制作用,其中对茎叶的抑制作用大于根系,根冠比增加。苗期亏水抑制了株高、叶面积和地上部物质的生长,复水后补偿效应明显;拔节期是缺水敏感期,拔节期亏水对株高、叶面积及干物质累积的影响差异极显著,复水后补偿效应不明显;灌浆期亏水对株高影响不明显,但对叶面积及干物质影响明显;成熟期亏水对玉米生长的各个指标没有显著的影响。施氮对玉米的生长及地下干物质的累积有一定的影响,在试验的土壤肥力水平下,表现为施纯N 0.1 g/kg的施氮水平对盆栽玉米的生长和发育最好,是适宜的施氮水平。水氮交互作用在拔节期和灌浆期对玉米地上部干重、根干重影响极显著,对根冠比分别达到极显著和显著水平,苗期和成熟期对各指标均无显著性影响。

春小麦调亏灌溉对土壤氮素养分的影响

本文对河西绿洲灌区春小麦调亏灌溉两年后的土壤碱解氮和全氮的变化进行了研究,并用配对样本t检验（双尾检验）对小麦收获时土壤氮素养分指标年际间的差异及其与全生育期调亏供水量间的关系进行了回归分析,旨在为该区春小麦调亏灌溉对土壤氮素养分的影响研究提供一些可靠的信息。结果发现,春小麦调亏灌溉对2003年和2004年两个试验年度0-20 cm、20-40 cm及0-40 cm土层土壤氮素养分有显著影响;而小麦收获时土壤氮素养分指标配对样本t检验发现,2004年0-20 cm土层土壤全氮、碱解氮,20-40 cm土层全氮,0-40 cm土层全氮显著高于2003年,然而20-40 cm土层碱解氮、0-40 cm土层碱解氮在2003年和2004年间差异不显著。0-40 cm土层土壤全氮量与小麦全生育期供水量呈线性负相关,而碱解氮则与全生育期供水量呈线性正相关。

基于临界氮浓度的宁夏玉米氮吸收与亏缺模型研究

以宁夏回族自治区当地玉米主栽品种天赐19为试验材料,设置6个氮素水平(0、90、180、270、360、450 kg/hm^2),研究滴灌玉米地上部生物量和氮累积动态变化,构建玉米临界氮稀释曲线模型,在此基础上构建氮吸收模型和氮累积亏缺模型,实现对滴灌玉米氮素营养状况的快速诊断。结果表明,滴灌玉米地上部干物质量增长和氮吸收累积均受施氮水平的影响,且随生育进程的推进呈上升趋势,氮累积量过高或过低均不利于产量形成,玉米植株存在氮奢侈消费现象;滴灌玉米临界氮浓度、最高和最低氮浓度与地上部干物质量之间均可用幂函数方程表示,其平均决定系数R^2分别为0.976、0.903和0.941,均达到极显著水平;基于临界氮浓度构建的氮吸收模型和氮累积亏缺模型对滴灌玉米生育期内氮素营养诊断结果一致,综合施氮量与产量的拟合曲线,推荐宁夏引黄灌区滴灌玉米施氮量以270~311 kg/hm^2为宜。研究结果可为宁夏引黄灌区滴灌玉米实现精准施肥和优化氮素管理提供理论参考。

不同生育期水分亏缺和施氮对冬小麦产量及水分利用效率的影响

【目的】研究不同生育期土壤水分亏缺和施氮对冬小麦产量及水分利用效率的影响,探讨小麦生长的水分亏缺敏感期和合理施氮量。【方法】以冬小麦小偃22为试验材料,设置4个氮肥水平和11个水分亏缺处理,采用盆栽试验,研究不同生育期水分亏缺和施氮水平对冬小麦水分利用效率、产量及其构成要素的影响。【结果】不同生育期土壤水分亏缺和施氮水平对冬小麦产量和水分利用效率有一定影响。与全生育期不亏水处理相比,返青期水分亏缺处理冬小麦干物质显著降低了7.70%,产量、水分利用效率显著增加了4.95%和7.56%;拔节期、抽穗期水分亏缺处理冬小麦干物质显著降低了13.69%,15.88%,产量显著降低了5.69%,8.06%,且对有效穗数、穗粒数也有显著降低作用;灌浆期水分亏缺对冬小麦产量影响不显著,但耗水量显著减少了5.44%,水分利用效率显著增加了8.02%。与全生育期不亏水处理相比,返青期+拔节期、返青期+抽穗期、返青期+灌浆期、拔节期+抽穗期、拔节期+灌浆期、抽穗期+灌浆期水分亏缺处理冬小麦干物质和产量均有显著降低,其中返青期+拔节期、拔节期+抽穗期水分亏缺处理冬小麦干物质显著降低了17.44%,17.57%,产量显著降低了11.60%和14.52%,水分利用效率显著降低了8.02%和7.56%,且对有效穗数、穗粒数也有显著降低作用。施氮对冬小麦产量和水分利用效率有显著促进作用。中氮处理(0.3 g/kg,N2)冬小麦产量最高,耗水量较低,水分利用效率较高。【结论】冬小麦对拔节期、抽穗期、返青期+拔节期、拔节期+抽穗期水分亏缺很敏感,中氮处理具有最高的产量和较高的水分利用效率。

调亏灌溉和施氮对玉米叶片保护系统的影响

通过盆栽试验,研究了不同生育期亏水和氮肥处理对春玉米叶片丙二醛(MDA)含量、可溶性糖(SS)含量、过氧化物酶(POD)和超氧化物歧化酶(SOD)活性的影响。结果表明,调亏灌溉可使玉米叶片MDA和SS含量明显升高,而使POD和SOD活性有所降低。施氮处理能保证叶片在抽雄期前SS含量、SOD和POD活性处于较高水平。MDA含量与灌水和施氮水平呈负相关,拔节后期达最大值,之后减小。从苗期到拔节后期,调亏灌溉施氮处理的可溶性糖含量较高,而高氮持续亏水处理可导致可溶性糖含量降低。POD活性到拔节后期达到最大,抽雄期有所降低。亏水处理明显降低了叶片POD活性,复水后补偿效应明显。施氮可适当提高POD活性,但抽穗亏水和全生育期亏水高氮处理在抽雄期的酶活性降低。SOD活性的变化趋势和POD相似。苗期亏水处理在复水后各生理生化指标补偿效果较好,拔节期亏水处理次之。高氮处理不宜在抽雄期调亏灌溉。调亏灌溉和施氮的最佳处理组合为苗期调亏低氮处理。