Monitoring forage production for farmers’ decision making

Objective management of grazing livestock production systems needs monitoring of forage production at the managerial unit level. Our objectives were to develop a system that routinely estimates forage above-ground net primary production (ANPP) at the spatial and temporal resolution required by farmers in the Pampas of Argentina, and to facilitate adoption of the system by end users as a managerial support tool. Our approach was based on the radiation use efficiency (RUE) logic, which proposes that ANPP is determined by the amount of photosynthetically active radiation absorbed by the canopy (APAR), and the efficiency with which that energy is transformed in above-ground dry matter (radiation use efficiency, RUE). APAR is the product of incoming photosynthetically active radiation (PAR) and the fraction absorbed by the canopy (fPAR). We estimated fPAR as a non-linear function of MODIS normalized difference vegetation index (NDVI). RUE was empirically estimated for the two principal forage resources of the region, yielding the following relations: ANPP = 0.6 × APAR + 12, (R² = 0.86; p < 0.001; n = 18) for the upland sown pastures, and ANPP = 0.27 × APAR + 26, (R² = 0.74; p < 0.001; n = 18) for the lowland naturalized pastures, with ANPP in g/m²/60 days and APAR in MJ/m²/60 days. The models were able to predict independent ANPP values with acceptable accuracy. Computational procedures were automated and run in a Relational Data Base Manager System that stored and managed all the information. The system is currently monitoring 212,794 ha in 83 farms and provides monthly ANPP values for the previous month and a history of the last 6 years. The data so generated show ANPP differences between the two major forage resources, considerable variability of a given month’s ANPP among years and paddocks, and contrasting among-farm differences in the efficiency of conversion of ANPP and forage supplements into beef production. The system was well accepted by end users who utilize it mainly for making near real time decisions according to last month ANPP, and explaining results of previous production cycles by incorporating ANPP as an explicative variable. However, there were differences among farmers in the degree of utilization, apparently related to the advisor’s attitude toward this new technology. Our results indicate that (1) forage production of large extensions can be monthly monitored at the paddock level by a small laboratory with capabilities in geographic information systems, and (2) advisors and farmers apply this information to their managerial decisions.     

荒漠化预警模型及其应用研究

分析了土地生产潜力的影响因子及其计算方法，从机理上分析各因子给未来荒漠化的发展趋势可能造成的影响，并从土地生产潜力退化基本原理出发，建立了荒漠化顸警模型。以疏勒河流域为背景，在GIS平台支持下，应用预警模型分析了该流域昌马灌区农业综合开发后的荒漠化趋势，对灌区荒漠化的发展趋势和潜在危险性进行了分析判断。     

Quality and maximum profit of industrial tomato as affected by distribution uniformity of drip irrigation system

The tomato industry reformed its system of payment by weight of tomato, introducing a corrective system based on percent level of fruit dry matter produced. Such a decision implies significant changes in the management of irrigation systems, with a need to emphasize the technological quality of the marketable product. Three levels of distribution uniformity of the irrigation system are analysed, and related production functions of crop yield and percent of dry matter are presented as well as their use on the optimisation of dry matter, expected revenues and seasonal applied water. Results are critically influenced by the distribution uniformity. They demonstrate the inter-relationship between crop production, percent fruit dry matter and irrigation management, and the importance of considering non-uniformity in the economic analysis of industrial tomato production. Decreases in uniformity lead to a reduction in dry matter production per unit land. Decreases in dry matter are also observed with increasing levels of seasonally applied water, with the optimal level always lower than the required for maximum yield. Such interaction suggests a continuous and inverse relationship between profit and water applied. However, due to the corrective system of payment, by levels of percent of dry matter produced, for some uniformity, the expected revenue follows the yield-water production function instead of the dry matter function. This fact introduces disturbances in the optimal water applied inducing higher than expected levels of water applied for profit maximisation. The simulated data also show that incentives to switch to new systems or management practices able to raise the distribution uniformity result more from profit losses than increases in water price.     

Determining crop-water production functions using yield–irrigation gradient algorithms

Crop-water production functions (CWPFs) are a useful tool for irrigation planning, but derivation of CWPFs by field experimentation is expensive, and traditional analytical techniques are not well suited to derivation of CWPFs. Physiologically based crop models provide a useful tool for simulation of agricultural experiments, but they have not been extensively applied to the task of CWPF determination. A new algorithm type based upon differential crop yield response to irrigation (“yield–irrigation gradients” [YIG]) is presented that uses these crop models to determine planning-level irrigation schedules and CWPFs. Three specific algorithms are developed within this type, varying in complexity, performance, and computational costs. Performance of the YIG methods is compared against a standard reference evapotranspiration method. In particular, the randomized iterative YIG (RIYIG) algorithm provides near-optimal results but at the highest computational costs of all the methods specified. All of the techniques presented have general applicability and are not limited to any one crop or location.     

试论农业机械化在建设社会主义新农村中的重要作用

建设社会主义新农村,是党中央从贯彻落实科学发展观、构建社会主义和谐社会的全局出发作出的重大战略部署,农业机械化发展必须适应农业现代化和建设社会主义新农村的需要,为我国实现农业现代化、解决“三农”问题,建设社会主义新农村作出农业机械化应有的贡献。     

基于Landsat数据的条件植被温度指数升尺度转换方法

以陕西省关中平原为研究区域,应用点扩散函数、混合像素面积权重法和中值像素变异权重法将基于Landsat卫星遥感数据反演的分辨率为30 m的条件植被温度指数(VTCI)干旱监测结果上推至930 m的干旱监测结果,并与Aqua MODIS数据反演的分辨率为930 m的VTCI干旱监测结果进行对比分析,以期为两种空间尺度的干旱监测结果的综合应用提供技术支持。以MODIS数据反演的VTCI为参考,应用相关系数、均方根误差、半变异函数的估计值和图像纹理特征等对尺度上推的VTCI进行评价。结果表明,点扩散函数和混合像素面积权重法的尺度上推效果均较好,而中值像素变异权重法的尺度上推效果较差,说明点扩散函数和混合像素面积权重法均适用于研究区域VTCI干旱监测结果的尺度转换,且点扩散函数的数据处理过程更为简单。典型样点VTCI的尺度上推结果表明,空间异质性越小,尺度上推的结果越好。     

机动车驾驶员疲劳状态的仿真分析研究

通过对驾驶员的驾驶操纵过程进行分析,应用传递函数这一经典控制理论工具,构建了驾驶员的行为操纵模型,并在MATLAB/Simulink仿真环境下实现,通过对机动车驾驶员的正常状态和疲劳状态进行仿真比较分析,表明驾驶员在疲劳状态时比正常状态时需要更长的操纵时间才能跟随着道路环境的变化,其果断性和灵敏性、实时性均下降很多,为进一步研究机动车驾驶员的疲劳状态奠定了理论基础。     

旋耕机整机试验模态分析

以试验模态分析为手段，研究ＩＧ－１８０Ａ旋耕机整机振动模态特征，讨论了模态参数和频响函数分析用于旋耕机设计的问题，提出了旋耕机减重设计中应综合考虑强度可靠性和刚度可靠性的观点，并指出了补偿整体刚度的几种途径。     

论农业机械化在新农村建设中的重要作用

以新农村建设带给农机化新的发展机遇为主线,结合武汉市以实施农村"家园建设行动计划"为抓手,建设社会主义新农村的实际,论述农业机械化在新农村建设中发挥的重要作用。     

温度对不同育成地水稻品种的生长及其物质生产的影响

以原产温带的日本晴三粳稻品种和原产热带的IR8两籼稻品种为材料,观察了16—30℃恒温对其生长和物质生产的影响。结果:在试验温度范围内,各个品种的植株均随温度升高而增高;但两类品种的株高感温指数有差异,IR8两品种的较低,日本晴三品种的较高。IR8两品种在30℃下分蘖数最大,日本晴三品种则是在25℃下,较有利于它们的分蘖。IR8两品种的CGR和NAR,以30℃下最大,日本晴三品种则以25℃下的最大,干物质生产量亦呈此趋势。所有供试品种都是在25℃下出叶最少,出叶间隔天数则以在20℃下为最快。