Azodyn: a simple model simulating the date of nitrogen deficiency for decision support in wheat fertilization

A dynamic soil–crop model was developed to predict the date on which N deficiency occurs for winter wheat crops in the temperate climate of Northwest Europe. It is based on the daily simulation of soil N supply and crop N requirement for the period during which N-fertilizer is usually applied to wheat crops, the end of winter until flowering. The soil sub-model was derived from the `balance-sheet method' used in France for nitrogen fertilization recommendations. It describes the net mineralization of various sources of organic matter (soil humus, crop residues, organic products). The crop sub-model simulates crop biomass production and its nitrogen content using a radiation use efficiency model and a critical dilution curve for nitrogen content. Both soil and crop sub-models require few parameters and inputs, most of which are readily available on commercial farms, together with daily climatic data. The model tested with various rates and timings of N application in three experiments accurately simulated the date on which nitrogen deficiency began in wheat crops. The interest in using the model for tactical and strategic approaches is discussed.     

华北地区冬小麦产量潜力分布特征及其影响因素

利用华北地区农业气象观测站作物资料,验证APSIM-Wheat作物模拟模型区域尺度有效性,结合1961-2007年47年逐日气候资料,分析冬小麦潜在产量、水分限制产量和水氮限制产量时空分布特征,明确了气候因素对冬小麦不同等级产量潜力分布特征的影响程度。对APSIM-Wheat模型在华北地区区域尺度上进行验证,结果显示区域化模型在华北地区有较好的适用性。华北地区冬小麦各层次产量在时间上总体呈下降趋势,空间上呈带状分布,不同层次产量空间分布特征有所差别：冬小麦潜在产量从东北向西南减少,水分限制产量从东南向西北递减,水氮限制产量从东向西先增加后降低在山东济宁地区达到最大;河北省为冬小麦潜在产量和水氮限制产量的高值区,同时为水分限制产量的低值区,增加灌溉是提高其产量的主要途径;山东省为冬小麦潜在产量和水分限制产量的高值区,水氮限制产量的低值区,增施氮肥是提高其产量的主要途径;河南省为冬小麦潜在产量的低值区,辐射是其主要限制因素。决定冬小麦潜在产量时空分布特征的最主要气候要素为生长季内总辐射,总辐射与潜在产量呈极显著正相关关系;决定冬小麦水分限制产量分布特征的最主要气候要素为冬小麦生长季内降水量,呈极显著正相关关系;气候要素对于冬小麦水氮限制产量空间分布特征的解释方差较小,仅为0.48,故土壤等其他因素对其空间分布影响较大。气候变化背景下,如不改变作物品种,冬小麦各级产量潜力呈下降趋势,造成其下降的主要原因为总辐射下降以及随积温增加冬小麦生长季缩短,决定冬小麦产量潜力空间分布的主要因素为总辐射和降水量。     

遥感信息应用于水分胁迫条件下的华北冬小麦生长模拟研究

由于初始土壤水分、灌溉量等变量的空间分布不易获得,区域尺度水分胁迫条件下作物生长模拟存在一定难度。本文在WOFOST模型本地化和区域化的基础上,采用调控型方法,重点探讨了利用MODIS数据反演的地表蒸散在大范围内估算土壤水分平衡过程中的参数或变量初始值,以实现水分胁迫条件下作物模型区域模拟的可行性。2002年模拟结果显示,引入遥感信息优化获得初始土壤有效含水量、返青期生物量及抽穗期灌溉量后,土壤水分的模拟效果得到改善;32个农业气象试验站点模拟产量的相对均方根误差（RRMSE）由0.63降至0.20;华北冬小麦模拟产量的空间分布与实际产量分布更加接近,产量低估的情况得到较好改善;河北、河南、山东3省平均产量的模拟误差分别为－4.9%、4.3%和8.6%。初步结果表明,结合卫星遥感信息通过优化方法在大范围内估算作物模型的相关参变量,以实现水分胁迫条件下作物模型的区域应用是行之有效的。     

不同质地土壤不同林龄巴旦木叶片及土壤养分动态变化研究

为探明新疆莎车县巴旦木主栽区不同土壤质地下巴旦木土壤养分和叶片营养水平分布特征,笔者分别以沙土和壤土质地巴旦木幼树林和盛果期林为研究对象,测定叶片及0~20、20~50cm深度土壤的有机质和养分含量,分析莎车县巴旦木不同土壤质地、不同发育阶段、不同生长时期土壤肥力状况及对矿质营养元素利用需求模型。结果显示：沙质土壤巴旦木园土壤碱解氮、有效磷、有机质水平较低,土壤速效钾、有效硫与钙含量丰富,镁浓度适中;壤土巴旦木园土壤有机质含量缺乏,速效磷、速效钾、有效硫与钙、镁含量丰富,微量元素中有效锌缺乏;壤质土全氮、有效磷、镁、铜、铁含量均高于沙质土,沙质土微量元素铜、锌、铁、锰含量均缺乏;而巴旦木不同发育期对土壤养分含量影响几乎一致;巴旦木不同树龄叶片在展叶期-果实膨大期-采收期的营养元素含量变化趋势大致相同,巴旦木对大量元素的吸收主要发生在果实膨大期和采收期;展叶期主要以吸收全氮、速效钾为主,膨大期主要吸收速效氮和有机质为主;对微量元素的吸收主要集中在果实采收期,并且主要以吸收铁、锰元素为主,锌次之;膨大期以硼为主,其它微量元素吸收较少。根据平衡施肥的原则得出：巴旦木果实膨大期和硬核期以增施氮磷肥为主,在硬核期以增施钾肥为主,期间适当补充树体所需的微量元素,在采收后或次年年初施足有机肥和氮肥。     

基于ALMANAC的山西省冬小麦模拟

为了准确的监测山西省冬小麦动态长势和预测产量,本研究使用ALMANAC作物生长模型对山西省洪洞县高、中、低产田的冬小麦产量进行了模拟。收集了模型需要的作物属性、土壤、气象及田间管理措施等众多参数并根据实际情况对参数进行了调整,结果表明：冬小麦模拟产量的相对误差(RE)为-7.8%~5.7%,叶面积指数的RE为-12.5%~13.6%,水地最大叶面积指数最大;与背景态相比生育期提前,叶面积指数水地变化不大,旱地低较多,温度主要是对生育期的影响,而水分则对叶面积指数产生较大影响。冬小麦的产量和叶面积指数的动态变化能够被ALMANAC模型较好地模拟;而且模型能够模拟不同水分条件下冬小麦的叶面积指数及气候变化对冬小麦影响。     

微生物菌剂与耕作方式对冬小麦土壤化学性状的影响

为了解不同的耕作方式和微生物菌剂施用下土壤化学性状的动态变化特征,在玉米秸秆还田的基础上,于冬小麦季通过田间小区试验,研究了旋耕和深耕2种耕作方式以及添加不同外源微生物菌剂条件下,冬小麦不同生育期土壤速效磷、速效钾、土壤微生物量碳氮的动态变化特征。结果表明,2种耕作方式下对土壤速效磷、速效钾、微生物量碳氮含量差异不显著,但小麦季不同生育期对这些的影响达到显著水平。旋耕方式下,施用（沼液+根际促生菌）和EM菌分别对土壤速效磷、土壤速效钾效果最明显;深耕方式下,施用（沼液 根际促生菌）和沼液分别对土壤速效磷、土壤速效钾效果最好;2种耕作方式下施用根际促生菌降低了土壤碳氮比值,有利于秸秆的腐解。土壤速效钾在小麦季收获期根区较非根区含量分别增加了44.31%（旋耕）和32.61%（深耕）。2种耕作方式下的根区土壤微生物量碳、氮显著高于非根区,且添加EM菌均能提高土壤微生物量碳、氮含量。     

Ergebnisse zur Ertragsbildung bei ökologisch orientiertem Winterweizenanbau auf Lößschwarzerdeböden in trockenen Lagen

Results of yield formation at ecological oriented winter wheat cultivation on Calcic Chernozem soil in arid areas
The influence were examined in field experiments of wheater elements (air temperature, precipitation), nitrogen fertilization, sowing rate and irrigation on the yield and yield formation of winter wheat stands. The average level of yields amounts to 81.3 dt/ha (76…93.8 dt/ha). Limiting factor for yields is the availability of water in the soil. In humide seasons 9…12 % higher yields were obtained then in dry seasons. Without nitrogen fertilization yields of winter wheat are lower by 18 % than with nitrogen fertilization. At very high level of N fertilization only vegetative biomass increases, and the water use efficiency decreases.
Increase in plants/m² caused a rise of vegetative biomass and of ears/m², kernels per ear strongly decreased in the same time. At winter wheat cultivation in low input farming systems without nitrogen fertilization high yields will be obtained with 320…370 plants/m² and 15,000 kernels/m². Nitrogen uptake from the soil amounts to 180 kgN/ha. Because of great amounts of inorganic in the soil (70…200 kgN/ha) sufficient nitrogen is available until heading of the wheat plants. The nitrogen supply of wheat plants in later stages of development is influenced by wheater conditions.     

Assessing innovative sowing patterns for integrated weed management with a 3D crop:weed competition model

Weed dynamics models are needed to design innovative weed management strategies. Here, we developed a 3D individual-based model called FlorSys predicting growth and development of annual weeds and crops as a function of daily weather and cropping practices: (1) crop emergence is driven by temperature, and emerged plants are placed onto the 3D field map, depending on sowing pattern, density, and emergence rate; plants are described as cylinders with their leaf area distributed according to height; (2) weed emergence is predicted by an existing submodel, emerged weed seedlings are placed randomly; (3) plant phenology depends on temperature; (4) a previously developed submodel predicts available light in each voxel of the canopy; after emergence, plant growth is driven by temperature; when shaded, biomass accumulation results from the difference between photosynthesis and respiration; shading causes etiolation; (5) frost reduces biomass and destroys plants, (6) at plant maturity, the newly produced seeds are added to the soil seed bank. The model was used to test different sowing scenarios in an oilseed rape/winter wheat/winter barley rotation with sixteen weed annuals, showing that (1) crop yield loss was negatively correlated to weed biomass averaged over the cropping season; (2) weed biomass was decreased by scenarios allowing early and homogenous crop canopy closure (e.g. reduced interrows, increased sowing density, associated or undersown crops), increased summer fatal weed seed germination (e.g. delayed sowing) or, to a lesser degree, cleaner fields at cash crop sowing (e.g. sowing a temporary cover crop for “catching” nitrogen); (3) the scenario effect depended on weed species (e.g. climbing species were little affected by increased crop competition), and the result thus varied with the initial weed community (e.g. communities dominated by small weed species were hindered by the faster emergence of broadcast-sown crops whereas taller species profited by the more frequent gap canopies); (4) the effect on weed biomass of sowing scenarios applied to one year was still visible up to ten years later, and the beneficial effect during the test year could be followed by detrimental effects later (e.g. the changed tillage dates accompanying catch crops reduced weed emergence in the immediately following cash crop but increased seed survival and thus infestation of the subsequent crops). This simulation showed FlorSys to predict realistic potential crop yields, and the simulated impact of crop scenarios was consistent with literature reports.     

灌溉量对小麦氮素吸收和运转的影响

在田间遮雨棚中研究了两种灌溉模式和两个冬小麦品种的氮素吸收和运转规律,在本试验条件下,开花期吸收的氮来自土壤的占75.77%～83.09%,到成熟期为79.31%～83.74%。灌浆期间灌水增加植株各器官吸收肥料氮的比例,而降低了吸收土壤氮素的比例。小麦籽粒氮素的67.47%～83.37%来自开花前营养器官的贮存氮,虽然叶片的总含氮量     

接种丛枝菌根真菌对麦秆分解和旱稻生长的影响

为探究丛枝菌根真菌对还田秸秆分解和作物生长的作用,以旱稻和麦秆为试验材料,利用盆栽试验研究接种AM真菌对麦秆分解率、氮素释放率、土壤酶活性以及旱稻叶绿素含量、根系活力、生物量的影响。结果显示:AM真菌的菌根定殖率为27.17%～28.53%。与秸秆还田不接菌处理相比,还田同时接种AM真菌处理显著促进了麦秆的分解率和氮素释放率,而且土壤蛋白酶、脲酶和纤维素酶的活性显著增加;秸秆还田同时接种AM真菌显著提高了旱稻第60天的根系活力和第90天叶片的总叶绿素含量,显著促进了地上部分和根系生物量的累积。在旱稻田接种AM真菌能有效促进麦秆的分解和土壤酶的分泌、增加旱稻的根系活力,有利于旱稻生物量的积累。     

不同冬季覆盖作物轮作对农田土壤碳氮影响

风蚀是干旱区农田生态系统中土壤质量降低的关键因素,冬季作物覆盖可有效减少农田的土壤风蚀。通过探究河西灌区不同冬季覆盖作物轮作复种绿肥对农田土壤碳氮影响,以期为构建合理的周年覆盖轮作模式提供理论依据。本研究在热量一熟有余两熟不足的河西灌区春小麦种植区把冬小麦、冬油菜两种冬季覆盖作物和绿肥还田处理嵌套种植形成：（1）春小麦—冬油菜—箭筈豌豆(WCP)、（2）春小麦—冬小麦—箭筈豌豆(WWP)、（3）春小麦—箭筈豌豆(WP)、(4)春小麦—春小麦(W,CK)不同种植模式,在360 kg/hm² (N2)、270 kg/hm² (N1)、0 kg/hm² (N0) 3个施氮水平下,研究不同轮作模式对农田土壤碳、氮含量的提升效应。结果表明：在同一种植模式下土壤有机碳、土壤可溶性有机碳、热提取态有机碳、硝态氮、氨态氮、微生物量碳氮含量随施氮量的增加而增加,但在氮肥减量(N1)的条件下,与常规施氮(N2)相比较WCP轮作模式土壤有机碳、土壤可溶性有机碳、热提取态有机碳含量及微生物量氮无显著降低。相同施氮条件下,轮作模式间差异不显著,但与CK间差异显著;其中,0~10 cm土层,WCP轮作模式土壤有机碳、土壤可溶性有机碳、土壤热提取态有机碳、硝态氮、氨态氮、微生物量碳氮含量平均较CK提高5.42%、9.78%、10.96%、20.51%、15.76%、18.94%;10~30 cm土层,提高9.54%、7.06%、12.99%、20.12%、16.51%、18.16%。因此,春小麦轮作冬油菜复种绿肥模式在氮肥减量条件下仍对农田土壤碳氮有明显的提升效应,为河西灌区良好的周年覆盖作物轮作模式。     

两种根系采样方法的对比及冬小麦根系的分布规律

用挖坑冲洗法和改良根钻法研究了耕层（0~30cm）和1m土体内冬小麦根系生物量及其空间分布。研究结果表明,用根钻在垄上、垄间和与垄相切3个位置取样的采样方法较挖坑冲洗法优越。冬小麦根系总量一般在抽穗前后达到最大,一般为2.5~3.5 t/hm2。收获期的总根量一般为2.0 t/hm2左右。严重的氮素短缺、干旱和盐分胁迫条件下,灌浆期的根总量明显减少,但深层根系比例相对较大。然而,从单穗平均根量来说,并不一定减少,连续5季不施氮肥条件下的单株根量甚至可能是水肥充足处理单株根量的1.5~2.0倍。水肥适宜条件下,抽穗期以后根系在土壤剖面中的分布从上而下大致每10cm减少一半,总根量可用公式 （R为总根量,y1为0~10cm土层的根量,单位：t/hm2）近似表示。     

基于升尺度方法的华北冬小麦区域生长模型初步研究 Ⅰ.潜在生产水平

作物生长模型是在田间尺度上开发的,而区域尺度上的作物生长信息更受决策部门的关注。作物模拟从单点研究发展到区域应用需要解决升尺度连接（Scaling-up）等一系列技术问题。本文利用以经纬度为权重的IDW空间插值法对气象数据和与温度有关的作物参数进行空间插值;根据华北冬小麦的品种地带性分布特点进行了冬小麦品种参数     

油菜光合作用与干物质积累的动态模拟模型

以生理生态过程为基础,构建了油菜光合作用与干物质积累的模拟模型。模型针对油菜特有的生态冠层结构,采用“三层模型”法,即通过对花、角果、叶三层分别计算光能截获和光合作用,利用高斯积分法计算每层的光合量而得出每日的冠层总同化量。模型充分量化了油菜生理年龄、温度、氮素、水分等因子对最大光合速率的影响,同时考虑了维持呼吸与生长呼吸的消耗。利用不同品种、不同播期、不同氮素水平下的干物质积累动态对模型进行了初步验证,结果表明模拟值与观测值吻合度较好,模型具有较强的机理性和预测性。     

Simulating winter wheat yields under temperate conditions: exploring different management scenarios

This paper describes a methodology for analysing management strategies to find best agronomic practices using a crop simulation model (CERES-Wheat). The study area is the estate of Imperial College at Wye, in the Stour Catchment, Kent, UK, an area highly suited to winter wheat production. The model is validated using historic crop performance data. Yield responses to differing sowing rates (range 200–450 seeds m⁻²), sowing dates and rates of nitrogen application (between 100 and 220 kg ha⁻¹) with soil types of medium to heavy texture were simulated under water-limited conditions using historical daily weather data. In model validation, observed yields ranged between 6.9 and 7.4 t ha⁻¹, while simulated ranges were between 6.9 and 7.8 ha⁻¹. The RSMD of the difference was small (0.24 t ha⁻¹) and non-significant. Optimum management practices (in terms of planting date, seed density and nitrogen application) were thereby defined. Also, simulations of potential yield (i.e. yield with no water and nutrient stress) were run for comparison. Results of this study reveal that the calibrated and validated CERES-Wheat model can be successfully used for the prediction of wheat growth and yield under conditions appropriate to Western Europe.     

Growth dynamics of winter wheat in the field with daily fertilization and irrigation

In a field experiment with fertilized and irrigated winter wheat the above-ground crop was sampled once a week. Phenological development, plant density and canopy height were recorded and the green surface areas of leaves, stems and ears were measured. Soil mineral nitrogen was sampled and the field climate monitored. There were four treatments. The daily irrigated/fertilized (IF) and daily irrigated (I) treatments were both irrigated by a drip-tube system. Liquid fertilizer was applied to IF following a logistic function according to calculated plant uptake. A total of 200 kg N ha⁻¹ was applied. Treatment I, control (C) and drought (D) were all fertilized once in spring with 200 kg N ha⁻¹. In treatment D transparent screens were used to divert rainwater. Dry matter production ranged between 1400 in D and 2352 g m⁻² in IF. The corresponding amount of nitrogen uptake ranged between 15.8 and 24.6 g m⁻². After harvest, soil mineral nitrogen was lowest in IF.
An increase in the availability of nitrogen and water enhanced total biomass production as well as grain yield and leaf area. The daily supply of nitrogen according to crop demand delayed nitrogen uptake and increased total uptake. The results suggest that when the nitrogen is supplied in accordance with crop demand, the efficiency with which the applied fertilizer is utilized increases and the risk for nitrogen leaching decreases.     

长期施用有效微生物肥对冬小麦-夏玉米生长和产量的影响

在多年连续定位试验研究的基础上,研究了不同施肥方式对冬小麦、夏玉米生长和产量的影响。结果表明:EM微生物堆肥能明显增加冬小麦和夏玉米的产量。EM微生物堆肥处理的年均总产比等量传统堆肥增产8.3%~8.9%,其中冬小麦增产8.3%,夏玉米增产8.2%~9.4%。EM微生物堆肥能在一定程度降低土壤容重,增加土壤含水量,改善作物的生长环境。EM微生物堆肥处理的冬小麦、夏玉米总光合势比等量传统堆肥分别高5%~36%,5.2%~14.3%,比化肥处理分别高19%~72%,19.6%~46.4%,随EM微生物堆肥施用量的增加差异更明显。EM微生物堆肥比较高的光合势加快了干物质的积累速度,从而提高了冬小麦、夏玉米的群体生长速率。     

六种稻田土壤冬季种植黑麦草功能效应研究

选取我国亚热带地区6种主要成土母质发育的水稻土,通过定位试验研究了黑麦草产量、碳氮环境效应和土壤微生物量变化。结果表明,6种稻田土壤冬季均适合生长黑麦草,黑麦草地上部和根系干物质产量,在河沙泥田表现最好,分别为11 324.8 kg hm^-2和8 227.3 kg hm^-2。6种稻田土壤黑麦草地上部和根系碳蓄积量均存在显著差异(P＜0.05),地上部分碳蓄积量在河沙泥田最高,为4 495.3 kg hm^-2;根系碳蓄积量在河沙泥田和麻沙泥田表现最好,分别为2 799.6 kg hm^-2和2 711.8 kg hm^-2;黄泥田最低,为1 852.9 kg hm^-2。而黑麦草氮蓄积量,在河沙泥田最高,地上氮蓄积量为238.1 kg hm^-2,地下氮蓄积量为60.1 kg hm^-2。6种稻田土壤微生物量碳和土壤微生物量氮,在种草区和冬闲田间差异均达到了显著水平(P＜0.05),除灰泥田外种草区均大于冬闲田,冬季种植黑麦草增加了土壤微生物商。     

Performance of DSSAT-Nwheat across a wide range of current and future growing conditions

Crop models are widely used in agricultural impact studies. However, many studies have reported large uncertainties from single-model-based simulation analyses, suggesting the need for multi-model simulation capabilities. In this study, the APSIM-Nwheat model was integrated into the Decision Support System for Agro-technology (DSSAT), which already includes two wheat models, to create multi-model simulation capabilities for wheat cropping systems analysis. The new model in DSSAT (DSSAT-Nwheat) was evaluated using more than 1000 observations from field experiments of 65 treatments, which included a wide range of nitrogen fertilizer applications, water supply (irrigation and rainout shelter), planting dates, elevated atmospheric CO₂ concentrations, temperature variations, cultivars, and soil types in diverse climatic regions that represented the main wheat growing areas of the world.DSSAT-Nwheat reproduced the observed grain yields well with an overall root mean square deviation (RMSD) of 0.89 t/ha (13%). Nitrogen applications, water supply, and planting dates had large effects on observed biomass and grain yields, and the model reproduced these crop responses well. Crop total biomass and nitrogen uptake were reproduced well despite relatively poor simulations of observed leaf area measurements during the growing season. The low sensitivity of biomass simulations to poor simulations of leaf area index (LAI) were due to little changes in intercepted solar radiation at LAI >3 and water and nitrogen stress often limiting photosynthesis and growth rather than light interception at low LAI.The responses of DSSAT-Nwheat to temperature variations and elevated atmospheric CO₂ concentrations were close to observed responses. When compared with the two other DSSAT-wheat models (CERES and CROPSIM), these responses were similar, except for the responses to hot environments, due to different approaches in modeling heat stress effects.The comprehensive evaluation of the DSSAT-Nwheat model with field measurements, including a comparison with two other DSSAT-wheat models, created a multi-model simulation platform that allows the quantification of model uncertainties in wheat impact assessments.     

Barley–hairy vetch mixture as cover crop for green manuring and the mitigation of N leaching risk

Adopting mixtures of legumes and non-legumes can be an efficient tool to merge the advantages of the single species in the fall-sown cover crop practice. Cover crop mixtures are supposed to provide an additional benefit in reducing N leaching risks as compared to pure legume thanks to the N trapping skill of the non-legume companion, but to our knowledge no data are available on the effect of mixed cover crops on N leaching. For this reason, in a three-year study we investigated the effect of barley (Hordeum vulgare L.) and hairy vetch (Vicia villosa Roth.) grown in 100% pure stands or in 50:50 mixtures on the N leaching below the rooting zone as compared to the bare soil. The NO₃-N concentration in the soil solution was monitored by suction cup lysimeters placed at 0.9 m depth during the whole growing cycle and after cover crop incorporation into the soil and the amount of leached N was calculated on the basis of estimated drainage.The mixture showed variable biomass accumulation and proportion in the biomass accumulated by companion species across years, but a rather constant N accumulation, with a biomass C/N ratio intermediate between those of the pure crops. In all years, the N trapping effect of the mixture was clear as it decreased NO₃-N leaching at the same level of pure barley, both during its own growing cycle and after cover crop incorporation into the soil. Pure vetch showed the highest N source potential as green manure but no NO₃-N leaching mitigation effect as compared to the bare soil. Thus we demonstrate here that a mixture of barley and vetch, which was already known to be a “self-buffered system” able to guarantee a good and rather stable N accumulation, is also a “buffering system” for the agroecosystems in the Mediterranean conditions by acting as a N trapping crop able to reduce N leaching.