垦单5号玉米制种技术措施

垦单5号具有早熟高产、品质好、适应广的特点。2000年2月通过黑龙江省品种审定委员会审定并命名为垦单5号。     

基于最小距离法的RADARSAT-2遥感数据旱地作物识别

利用雷达遥感技术进行作物识别是当前作物遥感监测的研究热点之一,但利用雷达遥感技术进行旱地作物识别的相关研究较少,该文以RADARSAT 2雷达遥感数据对两种旱地作物玉米和棉花进行识别。以河北省枣强县为研究区,对其区域内的玉米和棉花进行识别。首先分析了与卫星过顶时刻同步采集的作物参数与后向散射系数之间的相关性发现,在植株高度、生物量、作物含水量、叶面积指数这四个作物参数中,植株高度与后向散射系数的相关性最大,其次是作物含水量;同时,通过最小距离法应用多时相、多极化雷达遥感数据进行作物识别,其精度可达到85%,通过与资源三号光学遥感数据结合,其作物识别精度提高到了93%。研究结果表明,雷达遥感数据应用于旱地作物识别是可行的,雷达遥感数据与光学遥感数据的结合能提高旱地作物识别的精度。该研究为应用雷达遥感数据进行旱地作物识别提供了参考。     

Do crop purchase programs improve smallholder welfare? The case of Zambia's Food Reserve Agency

Government and parastatal crop purchase programs have regained popularity in sub-Saharan Africa, with many citing improving smallholder farmers’ welfare as a key goal. Yet there is limited empirical evidence on the topic. This paper analyzes the effects of the Zambian Food Reserve Agency's (FRA's) maize purchase activities on smallholder welfare. The FRA buys maize at a pan-territorial price that often exceeds market prices in surplus production areas. Using two household panel survey datasets spanning 15 years and exploiting variation in the scale of FRA activities over time, we employ fixed effects and control function approaches to estimate the effects of a smallholder household's maize sales to the FRA on its welfare, as well as the effects of more intense FRA maize purchase activity in a given district on the welfare of smallholder households in the district. Results suggest positive direct welfare effects on the minority of smallholders that sell to the FRA. We also find that, in the early years of the program, more intense FRA maize purchase activity in a district was associated with reductions in smallholder welfare, particularly among maize autarkic and net buying households. In later years, we find no evidence of such negative effects and some evidence of positive district-level effects on maize net buyers.     

The effect of household wealth on the adoption of improved maize varieties in Zambia

Production and price risks that could render input use unprofitable sometimes prevent rural households from benefiting from input technological change. The household’s ability to cope with such risks and hence benefit from input technological change is often positively related to its wealth or stock of productive assets. Empirical evidence, however, suggests a non-linear relationship between wealth and adoption of new agricultural technologies so that within a rural community, households on the lower wealth continuum behave differently from those on the higher level. Using farm level data collected from 300 randomly selected households in three districts of Zambia in 2004/2005 crop season, this paper first stratifies households into poorly- and well-endowed households based on their access to productive assets and estimates separate double-hurdle models for the adoption of improved, high yielding maize (IHYM) varieties for each group. The results show that factors influencing the adoption and use intensity of IHYM varieties differ between the two groups. This draws attention to the need for recommending wealth group-specific interventions to increase the adoption and use intensity of such varieties and their subsequent impacts on food security and general livelihoods of the households. The explicit testing for the possibility that differences in household wealth affect the way in which other variables influence adoption decisions is the paper’s unique contribution to the adoption literature.     

Determination of the international maize price: What is the growing role of Brazil and Ukraine?

This paper examines the relationships among maize prices for four countries to determine if newly emerging exporters, Brazil and Ukraine, influence the international price of maize. Our work focuses on each market's participation in the price discovery process rather than trying to determine a price leader. We find that the United States plays the largest role in price discovery, followed by Argentina, Brazil, and Ukraine. We also search for export thresholds and find that Ukraine's contribution to price discovery rises slightly when an export threshold of 2.3 million tons is reached. No export thresholds were found for Brazil. Export thresholds for Argentina were found but only have a minor impact on price relationships. We also found that price relationships vary considerably across seasons of the year.     

1978~2014年间中国玉米生产的时空特征变化研究

［目的］厘清中国玉米生产的时空变化特征,有助于保障玉米的持续、稳定供应。［方法］文章采用经验模态分解等方法,基于玉米总产、播种面积及单产3个指标,从全国和省域两个尺度系统分析1978~2014年中国玉米生产的时空特征。［结果］（1）研究期间,全国玉米产量增加了1.60亿t,其波动量呈现先增大后减小的趋势,波动指数的变化幅度不大; 玉米播种面积增加了1716万hm2,其变化趋势与玉米总产量的变化趋势基本一致;玉米单产从1978年的2802.7kg/hm2波动性增至2014年的5809.1kg/hm2,总体波动幅度大于玉米播种面积和总产量的波动幅度。（2）研究期间,省域玉米增加量呈现出“北高南低”的特征,中国玉米生产重心进一步北移;省域玉米播种面积增加量呈现出“北高南低”“西高东低”的特征,东北区和华北区的玉米播种面积进一步扩大;省域玉米单产增加量呈现出“西高东低”“北高南低”的特征,省域单产以趋势增长为主,但年际间的波动较剧烈。［结论］1978~2014年,省域间玉米生产分异特征明显,建议制定差别化的玉米生产策略。