不同水氮管理对蔬菜地硝态氮淋洗的影响

 通过3年（1999～2001）的田间定位试验研究了中国北方露地蔬菜种植中不同水氮管理方式对蔬菜地NO3--N淋洗的影响。结果表明，在蔬菜生长期内，通过减少灌溉水量不但能够降低蔬菜地水分渗漏量，而且明显降低蔬菜地NO3--N淋洗量。减少施氮量同样明显降低蔬菜地NO3--N淋洗量。说明在蔬菜生产中将施氮量降低到传统施氮量的20%～40%，土壤含水量保持在蔬菜生长的有效土壤含水量的50%～80%，能够明显降低NO3--N的淋洗风险，且蔬菜产量未受到影响。     

A simulation model-assisted study on water and nitrogen dynamics and their effects on crop performance in the wheat-maize system I: The model

Based on data collected from field experiments, a comprehensive model was built on the Ithink (a registered trademark of iSee Systems) platform to simulate the dynamics of water and nitrogen, and crop performance in the winter wheat-summer maize double cropping system of the North China plain. The model, consisting of seven sub models, i.e. weather generator, phenology, biomass, dry matter partitioning, water balance, nitrogen balance, and nitrogen absorption and partitioning, well reflects water and nitrogen use and their relationship with crop yield under field conditions. A vertical water movement equation is employed in the water balance sub model to account for movement between layers. Crop transpiration and soil evaporation are simulated separately according to potential evaporation, crop cover and a soil water deficit coefficient. Soil evaporation is from the surface layer only while crop transpiration comprises the total amount of water absorbed by the root system from all soil layers. The model considers that nitrogen transformations, transfers and uptake are fulfilled by root systems. Transformation of nitrogen as mineralization, fixation and denitrification are responsive to soil moisture and temperature. Nitrogen movement is simulated with a convection-dispersion equation with nitrate as the soil solute. Nitrogen absorption and partitioning sub model includes the effects of water and nitrogen supply, crop nitrogen demand and nitrogen content in various crop organs. The model can be used to simulate crop yield, water-and nitrogen-use efficiencies and water-nitrogen leaching to specific soil layers in different water and nitrogen management practices.     

稻田中氮素流失的田间试验与数值模拟研究

在上海青浦农田水利试验站进行田间试验,研究了淹灌稻田在排水条件下的氮素流失规律。在试验的基础上提出了氮素运移与转化的数学模型,对氮素的淋失动态进行了模拟研究。分析表明, 淹灌稻田的淹水层和剖面土壤溶液中氮素的主要形态为ＮＨ４＋ － Ｎ; 施肥后淹水层中氮素浓度衰减呈指数消退; 水稻生长期间, 氮肥损失的主要途径是气体损失,而淋失量相对较小。氮素损失与农田灌溉排水条件有关,因此应合理进行水位管理与调控。     

不同水氮处理对棉田氮素平衡及土壤硝态氮移动的影响

 【目的】探讨不同水氮管理策略对高产棉田氮素平衡及氮素移动的影响。【方法】设置田间小区试验,研究了常规灌水＋常规施氮、优化灌水＋优化施氮、常规灌水＋优化施氮、优化灌水＋优化施氮、常规灌水+不施氮处理条件下的棉田氮素平衡和土壤硝态氮动态。【结果】在常规水氮管理条件下,收获后表观损失量高达163—294 kg?hm-2,60—200 cm土层中硝态氮含量较播前有大幅增加,增量与表观损失的比值达到0.39—0.69;优化水氮管理条件下表观损失量仅为19—87 kg?hm-2;常规水氮处理不同层次土壤剖面上均呈现出硝态氮的积累,而且随灌水量加大累积峰下移,优化水氮管理土壤剖面硝态氮累积程度较小。【结论】在常规施氮体系中氮素的表观损失率达52%—68％,氮素随水移动到根层以下是重要的损失途径之一;本试验中采用的优化水氮管理方法显著减少了硝态氮的淋移损失。     

Modelling impacts of precision irrigation on crop yield and in-field water management

Precision irrigation technologies are being widely promoted to resolve challenges regarding improving crop productivity under conditions of increasing water scarcity. In this paper, the development of an integrated modelling approach involving the coupling of a water application model with a biophysical crop simulation model (Aquacrop) to evaluate the in-field impacts of precision irrigation on crop yield and soil water management is described. The approach allows for a comparison between conventional irrigation management practices against a range of alternate so-called ‘precision irrigation’ strategies (including variable rate irrigation, VRI). It also provides a valuable framework to evaluate the agronomic (yield), water resource (irrigation use and water efficiency), energy (consumption, costs, footprint) and environmental (nitrate leaching, drainage) impacts under contrasting irrigation management scenarios. The approach offers scope for including feedback loops to help define appropriate irrigation management zones and refine application depths accordingly for scheduling irrigation. The methodology was applied to a case study in eastern England to demonstrate the utility of the framework and the impacts of precision irrigation in a humid climate on a high-value field crop (onions). For the case study, the simulations showed how VRI is a potentially useful approach for irrigation management even in a humid environment to save water and reduce deep percolation losses (drainage). It also helped to increase crop yield due to improved control of soil water in the root zone, especially during a dry season.     

氮肥运筹对小麦-玉米轮作农田无机氮淋失的影响

以冬小麦品种石新616,夏玉米品种浚单20为试验材料,采用田间定位试验和原位淋溶装置的方法,研究了河北省山前平原高产农田不同氮肥措施对冬小麦-夏玉米轮作农田0～100 cm土体中氮素淋失的影响。结果表明:不同施氮处理0～100 cm土层的NO3--N淋溶量和累积量均随施氮量的增加而增大;不同施氮措施对0～100 cm土体中无机氮分布和累积量的影响顺序为OPT+N处理>FP处理>FP-S处理>OPT处理>OPT-N处理>CK,其中OPT处理的小麦和玉米产量显著增加,且小麦和玉米收获后土壤的无机氮累积量明显降低;小麦季硝态氮主要分布在20～40 cm土层,玉米季硝态氮主要分布在表层和深层土体中;过量施氮是造成土壤氮素淋失和累积的主要来源。综合考虑经济效益和生态效益,在秸秆还田条件下,施氮量减少20%的施肥措施(OPT处理)是值得推荐的施氮措施。     

模拟强降雨条件下硝态氮在土壤剖面的累积及淋溶研究

[目的]为了探讨硝态氮在土壤中累积和淋溶水平。[方法]采用野外冬小麦田间试验,选定不同降雨强度和施肥水平,分析土壤不同深度水分含量和硝态氮含量。[结果]降雨强度和土壤施肥水平是有效影响土壤氮素在土壤中运移和淋溶的重要因素,表现在:土壤降雨强度越大,施肥水平越高,会造成土壤中主要氮素类型硝态氮明显的流失。此外,土壤质地类型也是造成土壤氮素流失的重要因素,表现为土壤质地砂性越强,其淋溶效果越明显。[结论]土壤施肥水平和降雨强度是影响土壤氮素流失的重要因素。     

Evaluation of methods to determine residual soil nitrate zones across the northern Great Plains of the USA

A four-year study was conducted from 2000 to 2004 at eight field sites in Montana, North Dakota and western Minnesota. Five of these sites were in North Dakota, two were in Montana and one was in Minnesota. The sites were diverse in their cropping systems. The objectives of the study were to (1) evaluate data from aerial photographs, satellite images, topographic maps, soil electrical conductivity (EC_a) sensors and several years of yield to delineate field zones to represent residual soil nitrate and (2) determine whether the use of data from several such sources or from a single source is better to delineate nitrogen management zones by a weighted method of classification. Despite differences in climate and cropping, there were similarities in the effectiveness of delineation tools for developing meaningful residual soil nitrate zones. Topographic information was usually weighted the most because it produced zones that were more correlated to actual soil residual nitrate than any other source of data at all locations. The soil EC_a sensor created better correlated zones at Minot, Williston and Oakes than at most eastern sites. Yield data for an individual year were sometimes useful, but a yield frequency map that combined several years of standardized yield data was more useful. Satellite imagery was better than aerial photographs at most locations. Topography, satellite imagery, yield frequency maps and soil EC_a are useful data for delineating nutrient management zones across the region. Use of two or more sources of data resulted in zones with a stronger correlation with soil nitrate.     

Variable Rate Nitrogen Fertilisation of Winter Wheat Based on a Crop Density Sensor

Site-specific nitrogen fertilisation is important in precision agriculture. Based on positive results from a mechanical sensor (pendulum-meter) for the indirect measurement of existing plant mass in cereals, late nitrogen fertilisation in a farm scale strip trial was tested in the growing seasons of the year 2000 in one field and 2001 in two fields. The pendulum-meter was mounted at the front of a tractor. For site-specific fertilising, a tractor-mounted spreader which included an on-board computer was modified. The fertiliser rate was varied according to plant growth. In parts of the plots with low plant mass, the application rate was reduced and in parts with high mass increased. The result of site-specific fertilising was that, for the three fields calcium–ammonium–nitrate (CAN) could be saved in the range of 10–12% without reducing yields. The grain quality was not significantly influenced by low or high fertiliser rates.     

Sustainability of irrigated farming systems in a Tunisian region: A recursive stochastic programming analysis

The aim of this study was to evaluate the sustainability of farm irrigation systems in the Cébalat district in northern Tunisia. It addressed the challenging topic of sustainable agriculture through a bio-economic approach linking a biophysical model to an economic optimisation model. A crop growth simulation model (CropSyst) was used to build a database to determine the relationships between agricultural practices, crop yields and environmental effects (salt accumulation in soil and leaching of nitrates) in a context of high climatic variability. The database was then fed into a recursive stochastic model set for a 10-year plan that allowed analysing the effects of cropping patterns on farm income, salt accumulation and nitrate leaching. We assumed that the long-term sustainability of soil productivity might be in conflict with farm profitability in the short-term. Assuming a discount rate of 10% (for the base scenario), the model closely reproduced the current system and allowed to predict the degradation of soil quality due to long-term salt accumulation. The results showed that there was more accumulation of salt in the soil for the base scenario than for the alternative scenario (discount rate of 0%). This result was induced by applying a higher quantity of water per hectare for the alternative as compared to a base scenario. The results also showed that nitrogen leaching is very low for the two discount rates and all climate scenarios. In conclusion, the results show that the difference in farm income between the alternative and base scenarios increases over time to attain 45% after 10 years.     

种植玉米与休闲对土壤水分和矿质态氮的影响

【目的】研究不同种植模式下，农田土壤水分和矿质态氮的动态及其相互关系，对优化作物种植方式和养分资源管理，调控农田土壤硝态氮淋溶有重要意义。【方法】在黄土高原南部有大量氮素残留背景的田块上，研究了夏季多雨季节，种植作物与休闲对土壤水分与矿质氮的影响。【结果】在降水（含灌水82 mm）364 mm的夏季，休闲可使0～200 cm土层的贮水量达到600 mm，比播种前高204 mm，比种植作物高39 mm。种植作物的土壤水分可下渗至180 cm深的土层，休闲土壤中则可下渗到260 cm深处。种植作物时0～200 cm土层的硝态氮残留量为78 kg·ha-1，比休闲时减少89 kg·ha-1，且硝态氮主要分布在60 cm以上的土层。休闲时硝态氮却被淋到了220 cm深的土层。【结论】硝态氮向下层土壤的移动显著滞后于水分，夏季种植玉米可有效防止硝态氮向下层土壤的淋移。     

不同施氮水平下深层土壤硝态氮淋失特征研究

通过GeoprobeR深层取土18m,分析了不同施氮水平下厚不饱和层土壤中NO3--N的迁移变化。发现不同施氮处理下NO3--N在一个生育期的淋失变化主要体现在0～4m土体内,土壤中硝态氮累积峰下移深度为0.2～0.6m,高施肥土体中,深层土壤6.7～8m和13～15m土体中也有少量硝态氮淋失,施氮量越高,淋失量和累积量也越高;不同施肥处理下,厚不饱和层土壤中NO3--N累积量变化主要体现4m土体特别是根区土层中,在2m土体内,土体中NO3--N的累积量与施入的氮肥量呈极显著线性关系,根区以下不饱和层中NO3--N累积量超过1800kg/hm2。     

农业生态系统中氮素造成的非点源污染

施入农业生态系统（土壤）中的氮素,除一部分被作物吸收外,其余大部分经径流、淋溶、农田排水等形式流失。畜禽养殖场所排废水中的氮素也主要进入地表水和地下水中。氮素流入对水域的污染为非点源污染,主要导致地表水的富营养化、地下水硝酸盐含量过高等。解决途径是确定合理施肥量和平衡施肥,并对畜禽粪便进行处理利用。     

不同管理模式下农田水氮利用效率及其环境效应

 【目的】定量化不同水氮管理模式下的农田水氮利用效率和环境效应,为制定优化的水肥管理措施提供理论指导。【方法】在华北平原北部的冬小麦-夏玉米轮作区,设置了农民习惯和基于土壤水分养分实时监测的优化管理两种水氮管理模式。首先,应用田间系统的观测数据（2004年10月至2006年9月）对水氮管理模型进行了校验,然后应用校验后的模型计算得到了两种水氮管理模式下的作物产量、农田水分渗漏、氮素淋失、气体损失和水氮利用效率等。【结果】2年内农民习惯和优化管理下的灌水量差别不大,而优化管理的施肥量（540 kg N·hm-2）仅为农民习惯施肥量（1 100 kg N·hm-2）的一半。农民习惯和优化管理模式下的作物年平均产量分别为11 579和11 748 kg·hm-2;两者的水分利用效率分别为1.65和1.72 kg·m-3;氮素利用效率分别为15和24 kg·kg-1 N。氮素淋失和氨挥发是氮素损失的主要途径,农民习惯和优化管理下的氮素淋失分别为407和68 kg N·hm-2;氨挥发分别达到了282和104 kg N·hm-2。【结论】优化管理下的作物产量和水氮利用效率都高于农民习惯管理的,并且氮素损失明显低于农民习惯管理。因此,为了保证该地区的农业可持续发展,必须改进当前农民习惯的水氮管理措施。     

根层调控对小麦-玉米种植体系氮素利用及土壤硝态氮残留的影响

【目的】针对华北平原冬小麦-夏玉米轮作区高产田水肥资源利用效率低、氮素累积严重的问题,探索不同根层调控措施对作物氮素利用及土壤NO₃^--N残留的影响。【方法】以华北平原高产粮田为对象,设置传统水氮、水氮调控、调控+土壤调理剂（Agh）、调控+CRU（用含量为43%的缓释尿素代替氮肥）和调控+植物生长调节剂（GGR）田间小区试验,采集测定土壤、植株及根系样品,分析不同根层调控措施对氮素利用的效果。【结果】在控水减氮前提下,调理剂和GGR处理的小麦玉米周年产量、吸氮量均高于传统水氮。小麦拔节期GGR处理80-100 cm土层根系分布较多,表明GGR能促进中下层根系的发育;玉米大喇叭口期,藁城调理剂和大名GGR处理20-50 cm土层的根长密度均明显高于传统水氮。第一个轮作季,藁城和深州GGR的0-200 cm土体各土层硝态氮残留量均显著低于传统水氮,尤其在60-100 cm土层硝态氮的残留最低;第二个轮作季,藁城调理剂和大名GGR处理各土层硝态氮的残留量显著低于传统水氮。第一个轮作季的调理剂和第二个轮作季的GGR（藁城）的氮素表观亏缺量较大,说明根层调控促进了作物对土壤累积氮素的利用。根层调控措施能够达到经济和生态的双赢,灌溉水分利用效率（WUE）和氮偏生产力（PFP_N）较传统水氮平均提高了2.47 kg·m^-3和18.08 kg·kg^-1,平均增收258.43元/667 m²。【结论】在华北平原高产田,不同根层调控措施的小麦、玉米单季及周年的产量较传统水氮平均分别提高了8.58%、5.99%和7.13%;两季作物收获后0-100 cm土层中土壤硝态氮残留量较传统水氮平均分别降低了70.73和59.44 kg·hm^-2,明显降低了土壤硝态氮的残留,减缓了向土体深层的淋溶损失;促进了小麦、玉米关键生育期根系的发育。总之,通过在控水减氮的基础上添加土壤调理剂和植物生长调节剂（GGR）可以显著提高作物产量,能使其充分挖掘土壤累积氮素,实现节本增效,提高水肥利用效率。     

Agricultural management practices: Effects on soil properties,root growth and sesame yield

The influence of agricultural management practices, such as organic fertilisation and plant densities on soil properties, root growth, and sesame yield were investigated. Soil samples (depth of 0–20 cm) were taken from a field study with sesame (Sesamum indicum L.) cultivated on a Chromic Luvisol, which was conducted to explore the effects of six fertilisation systems [Non-fertilisation (Control); Mineral fertilisation (Min); Organic fertilisation with 2 (Org-1) and 3 Mg ha^–1 (Org-2) of commercial organic fertiliser Organus B; and with 1 (Tak 1) and 2 Mg ha^–1 (Tak-2) of commercial organic fertiliser Takamix] and two plant densities [111111 (Pdens1) and 55555 (Pdens2) plants ha^–1), in a factorial design (6 × 2) with four blocks. The highest values of soil organic carbon, total nitrogen, root density and sesame yield were found in the Org-2 fertilisation and Pdens1 treatments. We found that organic fertilisation combined with Pdens1 significantly increased root growth. Organic fertilisation treatments were able to maintain 80% of sesame roots distributed at a soil depth of 0–10 cm, whereas the last 20% were distributed at a soil depth of 10.1–20 cm. In conclusion the utilization of commercial organic fertilisers as an organic matter source enhanced soil organic carbon, total nitrogen, and root density that contributed to increase sesame yield. Our findings also suggest that inputs of organic matter source with a correct plant density might change positively soil organic carbon and total nitrogen, root growth, root distribution and sesame yield.     

深翻、有机无机肥配施对稻田水分渗漏和氮素淋溶的影响

【目的】针对我国长江中下游地区稻麦轮作区常年浅耕与不合理施肥导致的土壤犁底层增厚与土壤板结的问题,研究深耕（打破部分犁底层）与施肥方式对稻田土壤容重、土壤紧实度、土壤水分渗漏量、氮素淋溶量及氮素形态的影响,阐明稻田氮素淋溶量与耕作、施肥方式的响应机制,为稻田合理耕层构建提供理论依据。【方法】（1）基于2015年安徽省舒城县设置两种耕作方式（旋耕12 cm、深翻20 cm）、3种等氮量施肥方式（仅施化肥处理T1、秸秆还田配施化肥处理T2、有机与无机肥配施处理T3）的田间定位试验,2019—2020年监测土壤容重与紧实度以及稻季水分渗漏与氮素淋溶量。（2）通过原状土柱模拟试验,研究深翻30 cm（打破犁底层）对稻田水分渗漏量的影响。【结果】（1）田间试验结果表明,深翻20 cm较旋耕12 cm降低了耕层土壤容重与紧实度,但没有显著增加水稻生育期的水分渗漏量,仅在分蘖期增加7.4%,孕穗期之后无显著影响。（2）土柱试验结果显示,深翻30 cm（打破犁底层）水分渗漏量较旋耕12 cm和深翻20 cm显著增加,淹水时分别增加19.0%与11.0%,非淹水时分别增加23.0%与21.5%。（3）田间试验水分渗漏液中的氮素主要以硝态氮的形式存在,T3较T1和T2处理在水稻进入孕穗期后显著降低渗漏液中硝态氮的浓度;各施肥处理间铵态氮浓度差异不显著。（4）从整个水稻生育期看,两种耕作方式对氮素淋溶量影响不显著,而3种施肥方式下氮素淋溶量存在明显差异,T3处理降低了氮素淋溶量。深翻条件下T1、T2与T3处理氮素淋溶量分别为10.69、11.74和9.14 kg N·hm^-2,旋耕条件下分别为9.83、11.21和8.58 kg N·hm^-2。【结论】深翻20 cm可以改善土壤物理性状,但不会增加土壤水分渗漏及氮素淋溶;相同耕作方式下,有机与无机肥配施不会增加土壤水分渗漏与氮素淋溶。因此,在长江中下游黏质且犁底层厚（如红黄壤型）的水稻土区,部分打破犁底层,有机与无机肥配施,可构建深厚肥沃的耕作层,且不会增加水分渗漏和氮素的淋溶。     

Inverse meta-modelling to estimate soil available water capacity at high spatial resolution across a farm

Geo-referenced information on crop production that is both spatially- and temporally-dense would be useful for management in precision agriculture (PA). Crop yield monitors provide spatially but not temporally dense information. Crop growth simulation modelling can provide temporal density, but traditionally fail on the spatial issue. The research described was motivated by the challenge of satisfying both the spatial and temporal data needs of PA. The methods presented depart from current crop modelling within PA by introducing meta-modelling in combination with inverse modelling to estimate site-specific soil properties. The soil properties are used to predict spatially- and temporally-dense crop yields. An inverse meta-model was derived from the agricultural production simulator (APSIM) using neural networks to estimate soil available water capacity (AWC) from available yield data. Maps of AWC with a resolution of 10 m were produced across a dryland grain farm in Australia. For certain years and fields, the estimates were useful for yield prediction with APSIM and multiple regression, whereas for others the results were disappointing. The estimates contain ‘implicit information’ about climate interactions with soil, crop and landscape that needs to be identified. Improvement of the meta-model with more AWC scenarios, more years of yield data, inclusion of additional variables and accounting for uncertainty are discussed. We concluded that it is worthwhile to pursue this approach as an efficient way of extracting soil physical information that exists within crop yield maps to create spatially- and temporally-dense datasets.     

填闲作物消减蔬菜生产棚室土壤硝态氮潜力研究

为了明确填闲作物对棚室蔬菜土壤NO₃^--N的消减潜力, 揭示不同填闲作物消减土壤剖面累积NO₃^--N的特征, 并为探索阻控棚室蔬菜土壤氮素淋溶损失机制及预防地下水污染提供理论依据, 本研究以华北平原传统的棚室蔬菜轮作体系作为研究对象, 在蔬菜休闲期采用种植深根型填闲作物甜玉米、甜玉米+牛膝间作和白菊花的田间原位修复技术。结果表明:甜玉米和甜玉米+牛膝处理的总含氮量和吸氮量较高, 分别为20.11、19.62 t·hm^-2和240.34、287.56 kg·hm^-2, 显著高于白菊花的5.81 t·hm^-2和57.13 kg·hm^-2;根长密度和根干重均随土壤剖面深度的加深而降低, 其中白菊花处理的根长密度与根干重在0~30 cm土层显著高于其他处理, 30 cm土层以下的根干重在各处理间无差异, 根长密度在数值上表现为间作甜玉米> 甜玉米> 白菊花> 间作牛膝;甜玉米对土壤剖面0~200 cm土层的消减量高达907.87 kg·hm^-2, 显著高于白菊花的891.16 kg·hm^-2和甜玉米+牛膝间作的879.93 kg·hm^-2。因此, 在蔬菜作物轮作的间歇期, 种植填闲作物能有效地降低硝态氮在土壤中的累积, 控制土壤剖面硝态氮向下淋溶。     

大冲流域不同土地利用类型土壤的氮素淋溶模拟研究

为了解氮素在不同土地利用类型土壤中的淋溶过程,以具有代表性的、封闭的大冲流域不同土地利用类型土壤为研究对象,通过原状土柱试验,模拟806.4mm降雨量对其氮素淋溶过程的影响。结果表明:1)在不同土地利用类型土壤中,总氮、硝态氮和氨态氮淋溶总量的大小顺序分别为菜园地>坡耕地>梯平地>水稻田>杉木林地>混交林地>疏林地、菜园地>梯平地>坡耕地>疏林地>水稻田>杉木林地>混交林地和菜园地>杉木林地>疏林地>梯平地>水稻田>混交林地>坡耕地,其淋溶量的空间变异以坡耕地最大,水稻田最小。2)影响不同土地利用类型土壤氮素淋溶的因素有水解氮、全氮、自然含水量、比重、无定形铁和全钾等。结论:菜园地的氮素淋溶总量高于其他利用类型土壤,因此,在进行蔬菜种植时必须采取相应措施防止氮素淋溶损失造成水体污染。