二极管反向漏电流特性测试仪的设计

设计了一款在0~100℃和反向电压VR为0~1 000 V条件下,能够测试二极管反向漏电流特性的测试仪.它采用桥式输入I、CL7650组成的高精度放大电路、ADC0804和AT89S51完成了高压到低压的转换、信号的放大、采样、量化及显示,通过编程软件对测试结果进行修正,提高系统的测量精确度.对二极管IN4007的测试结果表明:所得反向漏电流分辨率达0.1 nA,准确度达1.79%.     

Growth,yield and water productivity of dry direct seeded rice and transplanted aromatic rice under different irrigation management regimes

Sustainability of traditionally cultivated rice in the rice-wheat cropping zone (RWCZ) of Pakistan is dwindling due to the high cost of production, declining water resources and escalating labour availability. Thus, farmers and researchers are compelled to find promising alternatives to traditional transplanted rice (TPR). A field study was conducted in Punjab, Pakistan, in 2017 and 2018 to explore the trade-offs between water saving and paddy yield, water productivity and economics of two aromatic rice varieties under dry direct seeded rice (DDSR) and TPR. The experiment was comprised of three irrigation regimes on the basis of soil moisture tension (SMT) viz., continuous flooded (>−10 kPa SMT), alternate wetting and drying (AWD) (−20 kPa SMT) and aerobic rice (−40 kPa SMT), maintained under TPR and DDSR systems. Two aromatic rice verities: Basmati-515 and Chenab Basmati-2016 were used during both years of study. In both years, DDSR produced higher yields (13–18%) and reduced the total water inputs (8–12%) in comparison to TPR. In comparison to traditional continuous flooded (CF), AWD under DDSR reduced total water input by 27–29% and improved the leaf area index (LAI), tillering, yield (7–9%), and water productivity (44–50%). The performance of AWD with regard to water savings and increased productivity was much higher in DDSR system as compared to AWD in TPR system. Cultivation of DDSR with aerobic irrigation improved water savings (49–55%) and water productivity (22–30%) at the expense of paddy yield reduction (36–39%) and spikelet sterility. With regard to variety, the highest paddy yield (6.6 and 6.7 t ha⁻¹) was recorded in DDSR using Chenab Basmati-2016 under AWD irrigation threshold that attributed to high tiller density and LAI. The economic analysis showed DDSR as more beneficial rice establishment method than TPR with a high benefit-cost ratio (BCR) when the crop was irrigated with AWD irrigation threshold. Our results highlighted that with the use of short duration varieties, DDSR cultivation in conjunction with AWD irrigation can be more beneficial for higher productivity and crop yield.     

兴电灌区主要带田养分循环与平衡研究

以兴电灌区6种主要带田种植模式为对象,采用田间实地调查,在典型地块划定小区按籽粒、秸秆和根茬三部分测重并取样分析化验的方法,研究了各模式的养分输入与输出状况及其养分循环与平衡特征。结果表明:除小麦/黄豆带田出现氮亏空外,其它5种带田种植模式的氮、磷、钾循环都是良好的,但其平衡条件是有足够的农家肥投入和有豆科作物的共生固氮。农家肥提供了总氮量4.62%~8.93%、总磷量17.34%~22.31%、总钾量72.61%~82.07%的养分;豆科作物提供了总氮量14.08%~42.45%的养分;化肥氮和磷占其养分输入总量的52.27%~76.06%和61.40%~70.91%;由降水和灌水携入的N,P,K分别占其养分输入总量的8.35%~12.04%,3.72%~7.74%和9.20%~17.48%。从施肥结构来看,6种带田种植模式的氮、磷、钾养分输入比例极不合理,在生产上应提倡控氮、增磷策略,同时注重化学钾肥的施用,并推行秸秆还田和高茬收割技术,以提高养分循环再利用的效率。     

基于灰色关联分析的农业生态系统能量产投研究

集成能量投入-产出分析和灰色关联分析方法,分析1961-2005年我国农业生态系统的能量投入-产出及能效率的变化,找出影响其变化的主导因素.结果表明:能量投入以畜力、有机肥和化肥为主,农业机械能和农业劳动力能比重小;随着能量投入的增加,单位耕地面积上的能量产出在波动中增长,1970年以来高于世界平均水平,但能效率在波动中下降.能效率与农业劳动力能和畜力能等传统动力能的关联性强,有机肥能投入减少对能效率的下降影响较大,化肥能的大量投入对总能量产出的贡献有限.因地制宜地增加机械能、提高有机肥能比重,有助于提高能效率.     

环境成本与生产投入的动力学分析

运用非线性理论研究企业环境成本与生产投入之间的动力学关系,预测环境成本与生产投入的发展趋势。     

南方红壤低丘岗地银杏园经营投入产出分析与比较

阐述了南方红壤低丘岗地发展银杏种植业的可行性并对各园种经营投入，产出作了分析与比较，据此提出了园种建议。     

农田防护林生态系统环境结构特征的研究——农田林网的辐射平衡

本文研究了农田林网的辐射状况,通过对林网内外直接辐射、散射辐射、反射辐射、总辐射、净辐射与光合有效辐射的比较,发现林网虽然减少了农田的总辐射,但可以增加净辐射和光合有效辐射,从而提高整个生态系统的能量输入.     

我国农产品加工业增值税政策的演变与问题分析

增值税是农产品加工业企业缴纳的主要税种,通过梳理农产品加工业增值税政策调整过程,分析现行政策存在的主要问题,提出从扩大农产品初加工的范围、采用消费型增值税、实行即征即退政策和改进进项税核定办法4个方面,完善增值税支持政策,促进农产品加工业快速发展。     

生态脆弱区耕地集约利用变化的能值分析

为了进一步分析生态脆弱区农地集约利用变化对区域农业经济和生态环境的影响,利用综合研究方法定量表征农业投入、产出、产投比的研究显得十分必要。以处于典型农牧交错区的宁夏盐池县为案例区,利用能值分析的计算方法探讨了研究区实施生态退耕后的2001-2008年耕地劳动力和农资投入、产出、产投比的动态变化特征。结果表明：随着种植面积的变化,单位面积劳动力投入总体呈下降趋势,而农资投入呈波动上升趋势;单位面积产出大幅度波动,而产投比呈波动下降趋势;产投比的波动方向受劳动力投入、农资投入和降水量的制约明显。研究结果显示,生态退耕后,单纯注重增加农资投入、扩大种植面积,而忽视高素质劳动力的投入以及因地制宜利用气候条件,可能是耕地产投比波动下降的原因;同时,研究区农资投入强度的增加,使农业面源污染风险加大。     

农业科技投入理论分析

综述了农业科技投入的经济增长理论、公共选择理论、市场理论,以期加快我国农业现代化进程,推进农业技术进步和制度创新。