An improved technique for agricultural implement draught analysis

Agricultural implement draft requirements show considerable spatial variability due to variations in soil properties and fracturing of soil. A large sample size is necessary to obtain a representative mean draft value for a given soil type and condition because of this variability. Moreover, empirical polynomial/multi-linear regression models for implement draft are often subjected to multi-collinearity problems. Proper design of experiments can assist in the complete elimination of these multicollinearity problems. An implement test procedure has been developed which addresses the problems of soil variability and multi-collinearity. Proper choice of values for independent variables in the experimental design phase can assist in transforming these variables to an orthogonal domain which completely overcomes multi-collinearity problems. The orthogonal regression technique using transformed variables and the conventional polynomial/multi-linear regression techniques using real variables were used to analyze draft data for a moldboard plow in a Capay clay soil to illustrate advantages of the orthogonal technique.     

微波干燥黄桃内部质热传递过程的模型

在Ｆｉｃｋ扩散模型和传导模型基础上考虑热湿扩散、水分直接蒸发及内热源的影响，获得了微波干燥黄桃时内部质热传递模型。模型模拟采用显式有限差分求解，计算值与实测值基本吻合。     

平衡施肥对马铃薯产量及品质的影响

通过平衡施肥对马铃薯产量和品质影响的研究,结果表明:在当地条件下,马铃薯最佳经济施肥量为N141 15kg/hm2,P2O5104 55kg/hm2,K2O198 90kg/hm2,施用比例1 0 74 1 41,最佳产量31845 30kg/hm2,施肥利润3306 90元/hm2,投产比1 3 63。采用平衡施肥能增加马铃薯产量,降低薯块硝酸盐和还原糖含量,并能增加淀粉含量,从而提高马铃薯产品品质,增加效益。马铃薯硝酸盐含量随氮肥施用量增加而增加,施用磷钾肥能明显降低硝酸盐含量。我区马铃薯生产重金属污染均未超标,符合国家食品卫生标准。     

农业用水及其生态社会效应的研究

研究建立了农业用水水资源城市人口非线性动力学模型,并探讨了农业用水的生态效应和有关稳定性问题。研究结果表明水资源城市人口 农业用水三者之间关系是非常复杂的非线性关系,盲目、超规模的农业用水将使城市城镇化抑或城镇农村化;稳定的城市人口与农作物生物总量成线性关系,低灌溉效率下农业用水的增加非但不能使农业增产,还将导致农作物生物总量的减少和城市规模的减小;为达到增加农业用水时既可使农业增产,又支持城市扩大的目的,惟一途径是提高农业灌溉效率     

微灌系统田间管网设计的一种模拟模型

微灌系统田间管网的设计是系统设计的中心环节,计算繁琐。本文利用常用的微灌系统水力学公式建立了一种实用的田间管网设计模拟模型。它适用于各种微灌系统的辅助设计。     

江西省生态农业发展对策

简析了江西省生态农业建设现状、生态农业主要模式及效益,并提出发展对策。     

种植作物条件下粉砂壤质土壤水盐运移的数值模拟研究

利用大型水盐运动模拟土柱研究了在田间气候作用下作物 (小麦 玉米连茬种植 )生长对土壤水盐运移的影响。研究并建立了土壤水盐运移的数学模型 ,就模型所需的饱和导水率、水力传导度、水分特征曲线、水动力弥散系数进行了室内外测定 ,并对数学模型进行了数值求解。对四个土柱的模拟结果与实测结果进行了数据分析和对比。结果表明 :数值模拟结果和实测数据比较 ,除个别点有一定偏离之外 ,模拟计算结果与实测值拟合效果比较理想 ,说明该模型用于模拟种植作物条件下粉砂壤质土壤的水盐运移是实际可行的。     

黑河流域生态环境建设分区研究

分区是实现区域合理配置的基础和前提,以可持续发展理论和《全国生态环境建设规划》为原则,以自然地理分异规律,现代生态学和经济学理论为依据,在原有各类专题分区和区域规划基础上结合当地自然经济状况,建立了新的生态环境建设分区指标体系。依据SPSS软件聚类分析结果,将黑河流域生态环境建设划分为3个大区4个亚区,并分析了各类型区特点,提出生态环境建设模式。     

Prioritisation of Philippine Island avifaunas for conservation: a new combinatorial measure

Given the ubiquitous fact that resources for preserving whole faunas are limited, prioritisation of areas is called for. The popularity of the complementarity approach for setting priorities derives from their representing the maximum number of species of a taxon with a minimum number of areas, e.g. islands in an archipelago like the Philippines. While the logic of the approach is impeccable, it lacks dynamism. Here a new approach to prioritisation is exemplified with avifaunas in the Philippines. A combinatorial, linear model permits assigning to each island avifauna a priority index that allows ranking of islands in terms of prioritisation. The model is (1) dynamically proactive in that it takes into account the island-specific ongoing and future dieback of the avifaunas at stake; by applying the well-established species-area relationship to the remaining forests as the new islands; (2) it is accountable by operationalising the weighting of its parameters by introducing the new quantity ‘opportunity for choice’; (3) it is combinatorial, being thereby more realistic. The model's results for the six largest Philippine islands were reasonably well validated based on a ranking of island-specific number of endangered endemics. The results lead to assigning the Greater Negros faunal region (Negros, Panay) top priority, similar to more species-rich Greater Luzon and Greater Mindanao, thus substantially changing the ranking of islands derived from the rather static one-parameter complementarity approach.     

Rates of decomposition of plant residues and available nitrogen in soil, related to residue composition through simulation of carbon and nitrogen turnover

The dynamics of inorganic N in soil following the application of plant residues depends on their composition. We assumed that all plant materials are composed of similar components, each decomposing at a specific rate, but differ in the proportions of the various components. The NCSOIL model that simulates C and N turnover in soil was used to link the rates of residue decomposition to their composition, defined as soluble, cellulose-like and lignin-like C and N, and thereby integrate short and long-term effects of residues on available N dynamics in soil. Five plant residues in a wide range of C:N ratios were incubated in soil for 24 weeks at 30 °C, during which C and N mineralization were measured. The materials with large C:N ratios (corn, rice hulls and wheat straw) were also incubated with NH₄⁺-N to avoid N deficiency. The residues were analyzed for total and soluble C and N. The partitioning of insoluble C and N between cellulose- and lignin-like pools was optimized by best fit of simulated C and N mineralization to measured results. The decomposition rate constants of the soluble and lignin-like pools were assumed to be 1.0 and 10⁻⁵ d⁻¹, respectively, and that of the cellulose-like pool, obtained by model optimization against mineralization of cellulose with NH₄⁺-N in soil, was 0.051 d⁻¹. The optimized, kinetically defined lignin-like pool of all residues was considerably larger than lignin contents normally found in plant residues by the Van Soest procedure. Gross N mineralization of tobacco and rape residues was similar, but N recovery from tobacco was larger, because a larger fraction of its C was in the lignin-like pool. N in rice hulls, corn and wheat residues was mostly recalcitrant, yet rice hulls did not cause N deficiency, because most of its C was recalcitrant too. The soluble components of the residues had strong short-term effects on available N in soil, but the cellulose-like pool was equally important for short and medium-term effects. Soluble and cellulose-like C were 29 and 42% of total C, respectively, in corn and 7 and 50% in wheat. Maximal net inorganic N losses, measured in both residue treatments after 2 weeks, were 42 mg g⁻¹ C applied as corn and 31 mg g⁻¹ C applied as wheat, or 84 and 110 mg g⁻¹ decomposed C of corn and wheat, respectively. Rice hulls immobilized N slowly, but by the end of 24 weeks all three residues immobilized 26-27 mg N kg⁻¹ C applied. The different dynamics of N immobilization demonstrated the need to determine the decomposability of C and N rather than their total contents in plant residues.