不同施氮量对加工番茄生长及土壤氮素平衡的影响

【目的】 研究不同施氮量对加工番茄生长及土壤氮素平衡的影响。【方法】 基于临界氮浓度模型的施肥方案,设置不施氮(N₀)、施氮200 kg/hm²(N₁)、施氮300 kg/hm²(N₂)和施氮400 kg/hm²(N₃)4个处理,测定加工番茄各生育期的生长、产量和土壤氮素等指标。【结果】 (1)在苗期阶段,各处理对加工番茄的生长无显著差异;坐果期后,N₂处理较其他处理可有效促进加工番茄的生长。2018年,红熟期N₂处理下的加工番茄株高为85.5 cm,显著高于其他处理,同期N₂处理下的茎粗为18.40 mm,显著高于N₀处理,但与其他施氮处理无显著差异,且2019年有同样变化趋势。(2)各处理土壤硝态氮主要分布在20-40 cm土层中,各土层中硝态氮含量随施氮量的增加而增加;2018年在拉秧期N₃处理下的硝态氮含量主要残留在40 cm以下土层中,占总硝态氮含量的54.72%,且2019年有同样趋势,淋洗风险较大;N₂处理下的土壤硝态氮分布较均衡,可以有效降低土壤氮素的残留,提高氮肥利用率。(3)土壤剖面中硝态氮盈余量随施氮量的增加呈增加趋势;N₀、N₁、N₂处理下的氮素主要以作物吸收的方式带出土壤,N₃处理下的氮素主要残留在土壤中;N₁处理可降低氮素在土壤中的残留量,但也降低了氮素的利用率,N₂处理有利于提高氮肥表观利用率,降低氮肥表观残留率,N₃处理促进了作物对氮素的吸收,但加大了氮素在土壤中的残留,降低了氮素利用率。【结论】 在基于加工番茄临界氮浓度模型的氮素运筹方案下,加工番茄苗期阶段,按N₁处理施44 kg/hm²减氮施肥,在开花期以后,施氮按N₂处理施234 kg/hm²的氮运筹可促进植株生长,且土壤氮素残留相对较少,保证了较高的氮肥利用率和经济效益。     

松嫩平原地下水氮污染空间变异性及健康风险评价

为探明松嫩平原地下水污染现状及氮污染影响,利用地统计学软件分析了“三氮”(硝态氮、亚硝态氮和铵态氮)含量的特征,采用ArcGIS绘制了地下水硝态氮的变异函数图和空间分布图,并应用健康风险评价模型进行了氮污染对人体的潜在健康风险评价。上述研究表明,该区地下水污染物以“三氮”最为突出,其中硝态氮污染最重,变异系数为1.686,属于强变异,含量分布与二阶球状模型拟合最好,块金值和基底效应分别为2.423和0.575,其含量的空间异质性是结构性因素及随机性因素共同造成的,随机性因素稍强;硝态氮污染高风险区占总面积的88.78%,主要分布在东中部高平原区,这一区域大部分为III类水,对人体健康存在较高的风险,应引起关注。     

科尔沁沙地不同土地利用结构硝酸盐氮淋失规律

采用小型回填式土柱动态淋溶实验方法,研究了科尔沁沙地不同土地利用结构耕层土壤硝酸盐氮淋失规律。结果表明,科尔沁沙地草地、林地和沙荒地结构淋溶液硝酸盐氮浓度平均值低于地下水Ⅰ类水质标准(2.0mg·L-1),农田结构淋溶液硝酸盐氮浓度平均值大于地下水Ⅰ类水质标准。农田结构是造成地下水硝酸盐氮污染的重点区域。科尔沁沙地不同土地利用结构硝酸盐氮淋失强度依次为:农田(96.54kg·hm-2·a-1)>沙荒地(32.84kg·hm-2·a-1)>林地(28.66kg·hm-2·a-1)>草地(15.48kg·hm-2·a-1)。农田是科尔沁沙地氮素营养管理的重点结构,硝酸盐氮淋失强度与土壤硝态氮含量呈极显著正相关。     

秸秆还田和氮肥用量对冬小麦产量和氮素利用的影响

【目的】在陕西关中小麦-玉米轮作区通过连续7年田间定位试验,探索秸秆还田配施化学氮肥对冬小麦产量、籽粒蛋白质含量、地上部吸氮量、收获期土壤硝态氮残留量及土壤氮素平衡的影响,为小麦增产及氮素高效利用提供科学依据。【方法】试验采用裂区设计,主处理为玉米秸秆还田和不还田,副处理设置5个施氮水平,分别为0（N0,不施用氮肥）、84 kg·hm^-2（N84,当地推荐氮肥用量的一半）、168 kg·hm^-2（N168,当地推荐氮肥用量）、252 kg·hm^-2（N252,高氮肥用量）、336 kg·hm^-2（N336,超高氮肥用量）。【结果】与秸秆不还田处理相比秸秆还田未提高冬小麦籽粒产量,施用氮肥较不施氮肥小麦增产18%—29%,而超高氮肥用量较推荐氮肥用量有减产风险。秸秆还田和氮肥用量对小麦产量有交互效应。与秸秆不还田处理相比,秸秆还田在氮肥用量为252和336 kg·hm^-2时,公顷小麦穗数增加5%—7%,产量平均增加5%—6%。秸秆还田对小麦籽粒蛋白质含量无显著影响,施用氮肥的籽粒蛋白质含量较不施用氮肥增加16%—33%。秸秆还田对小麦地上部吸氮量无显著影响,施用氮肥的地上部吸氮量较不施用氮肥增加36%—72%。秸秆还田和氮肥用量对小麦地上部吸氮量有交互效应。与秸秆不还田处理相比,秸秆还田在氮肥用量为252和336 kg·hm^-2时地上部吸氮量平均增加5%—8%。与秸秆不还田相比,秸秆还田使土壤硝态氮残留量平均增加18%,增加的硝态氮含量主要分布在70—170 cm土层。N168处理在秸秆不还田条件下土壤氮处于亏损状态,秸秆还田后有效地弥补了氮亏缺,进一步增加氮肥用量,将大幅增加土壤氮盈余量。相对于秸秆还田,氮肥用量对土壤氮盈余量的影响更大。【结论】秸秆还田配施高氮肥用量能增加小麦产量和地上部吸氮量,但同时增加了土壤硝态氮残留量和氮盈余量。综合考虑小麦籽粒产量、土壤硝态氮残留和土壤表观氮平衡等,秸秆还田配施168 kg·hm^-2氮肥更利于维持小麦产量和保护生态环境。     

Nitrogen best management practice for citrus trees: II. Nitrogen fate,transport, and components of N budget

Soils in central Florida citrus production region are very sandy, hence are vulnerable to leaching of soluble nutrients and chemicals. The objective of this study was to develop nitrogen (N) and irrigation best management practices for citrus in sandy soils to maintain optimal crop yield and quality, and to minimize N leaching below the rootzone. A replicated plot experiment was conducted in a highly productive 20+ year-old ‘Hamlin’ orange [Citrus sinensis (L.) Osbeck] trees on ‘Cleopatra mandarin’ [(Citrus reticulata Blanco)] rootstock grove located on a well drained Tavares fine sand (hyperthermic, uncoated, Typic Quartzipsamments) in Highland County, FL. Nitrogen rates (112–280 kg ha⁻¹ year⁻¹) were applied as fertigation (FRT), water soluble granular (WSG), a combination of 50% FRT and 50% WSG, and controlled release fertilizer (CRF). Tensiometers were used to monitor the soil moisture content at various depths in the soil profile as basis to optimize irrigation scheduling. Fruit yield and quality and nutritional status of the trees were reported in a companion paper. Soil solution was sampled at 60, 120, and 240 cm depths under the tree canopy using suction lysimeters. Concentrations of NO₃-N in the soil solution at 240 cm deep, which is an indicator of NO₃-N leaching below the tree rootzone, generally remained below the maximum contaminant limit (MCL) for drinking water quality (10 mg L⁻¹) in most samples across all N sources and rates, but for few exceptions. Total N in the fruit was strongly correlated with fruit load, thus, at a given N rate N removal by the fruit was lower during years of low fruit yield as compared to that during the years of high fruit yield. Furthermore, there was a strong linear relation between N and K in the fruit. This supports the need to maintain 1:1 ratio between the rates of N and K applications. In a high fruit production condition, the N in the fruit accounted for about 45% of the total N input on an annual basis. Fifteen percent of the total N input at 280 kg N ha⁻¹ year⁻¹ was not accounted for in the citrus N budget, which could be due to leaching loss. This estimate of potential leaching was very close to that predicted by LEACHM simulation model. The improved N and irrigation management practices developed in this study contributed to an improved N uptake efficiency and a reduction in N losses.     

不同施肥处理对作物产量及土壤中硝态氮累积的影响

通过4a定位试验研究了小麦-玉米轮作制度下不同施肥处理对作物产量及硝态氮(NO3--N)在土壤中累积和分布的影响。结果表明:长期大量施用氮肥,会造成土壤NO3--N的累积,且土体NO3--N的含量随施氮量的增加呈直线上升趋势;在土壤空间差异不显著的情况下,NO3--N在400cm土体中的分布呈一定的规律性,分别在60cm和200cm左右存在累积峰;配合施用磷肥、钾肥可以降低土壤剖面NO3--N的含量,尤其是钾肥可显著降低土壤上层NO3--N的含量,但作物无法吸收的NO3--N却有整体下移的趋势。提出华北山前平原高水肥投入地区NPK合理施用量为:N肥200kg/(hm2·a),P肥32.5kg/(hm2·a),K肥150kg/(hm2·a)。     

华北地区小麦-玉米种植制度下硝态氮淋失量研究

应用水量平衡法计算土壤水的下渗量,通过suction cup采集土壤溶液并测定其中硝态氮含量,不同施肥处理下不同作物的硝态氮淋失量分析结果表明:2001~2002年,冬小麦生长季硝态氮的淋失损失严重,其中施N量200,400,800 kg/(hm2.a)3个施肥处理180 cm土层淋失的硝态氮量分别为0,22,110 kg/hm2。玉米生长季也存在硝态氮的淋失,上述3施肥处理180 cm层次淋失的硝态氮量分别为2,16,50 kg/hm2。     

Influences of feedstock and pyrolysis temperature on the nitrate adsorption of biochar

Biochar (BC), charcoal produced through the pyrolysis of biomass, is reported to adsorb dissolved nitrate-nitrogen (NO₃-N). The NO₃-N adsorption properties of BC differ depending on the feedstock and the pyrolysis conditions, and the influences have not been systematically clarified. Therefore, we evaluated the dependence of feedstock and pyrolysis temperature on the NO₃-N adsorption properties of BC. Wood chips [Japanese cedar [Cryptomeria japonica] (CE) and Japanese cypress [Chamaecyparis obtusa] (CY)], moso bamboo [Phyllostachys edulis] chips (MB), rice [Oryza sativa] husks (RH), sugarcane [Saccharum officinarum] bagasse (SB), poultry manure (PM) and domestic wastewater sludge (WS) were air-dried and heated in a batch-type carbonization furnace at pyrolysis temperatures of 400, 600 and 800°C, with a hold time of 2 h. Among the BC produced from each feedstock, the one produced at 800°C had the greatest NO₃-N adsorption. The NO₃-N adsorption by BC produced from wood-based biomass at 800°C was significantly higher than that of the BC produced from non-wood-based biomass at 800°C. Therefore, BC made from wood-based biomass at higher temperature can be adequate as soil amendment material for adsorption of NO₃-N.     

不同棉田暗管布置方式对氮素流失影响的模拟分析

为了研究不同棉田暗管布置方式对暗管排水中硝态氮流失量的影响,结合2007—2009年在湖北荆州丫角排灌试验站的控制排水试验,采用DRAINMOD田间水文模型进行数值模拟。结果表明,暗管出口高程和暗管间距对暗管排水中的硝态氮流失量均有极显著的影响,是进行农田控制排水设计的关键因素。具体而言,暗管排水中硝态氮的流失量随着暗管出口高程的减小而减小,随着暗管间距的增大而减小。因此,在进行农田控制排水设计时,应根据当地的环境要求以及作物的具体生长要求,调整暗管的出口高程和暗管间距,做到作物高产和环境保护的统一。     

容重对土壤水氮垂直运移特性影响

为研究不同土壤容重下红壤土与黄土中水分与硝态氮垂直一维入渗运移特性差异,提高红壤与黄土地区水肥利用效率,以江西壤黏土与西安粉壤土为研究对象,采用垂直一维入渗方式模拟土壤容重对2种土壤中水分及硝态氮垂直运动规律的影响.结果表明:江西壤黏土与西安粉壤土的湿润锋运移距离及入渗速率均与土壤容重呈负相关;灌水结束时与再分布1 d后,2种土壤的含水率均与土壤容重呈负相关,西安粉壤土的含水率略大于江西壤黏土;土壤容重越大,硝态氮越集中于深层土壤中且其峰值越高,再分布过程中峰值下降,其中容重为1.25,1.35,1.40 g/cm³的峰值下降较大.灌水结束时土壤容重对40~50 cm土层内的硝态氮质量比在0.05水平下均具有统计学意义;再分布1 d后,2种土壤在0~30 cm土层内的硝态氮质量比相差甚小,在30~60 cm土层内的硝态氮质量比均较高,但西安粉壤土的硝态氮质量比更高.故江西壤黏土中硝态氮更容易淋溶,而西安粉壤土的持水持肥性较好.