新疆棉花的比较优势:基于粮棉单产比的分析

1992～ 1998年新疆、山东、安徽及全国的粮棉单产比分别为 3.75、7.2 4、6 .35、和 5 .0 7,新疆比山东和安徽分别低 3.5和 2 .6。回归分析表明 ,粮棉单产比每下降 1,来年棉产上升 7.8%。综合考虑农民人均收入、棉花运输成本及WTO等因素 ,在皮棉产量达到 175× 10 4 t之前 。

吉林省主要粮食作物生产风险评价

充分认识吉林省主要粮食作物生产面临的风险,为稳定粮食产量和保障国家粮食安全提供参考。以县级行政单元为研究对象,在运用直线滑动平均法对作物单产进行趋势模拟的基础上,运用非参数信息扩散模型对吉林省玉米、水稻和大豆3种主要粮食作物的生产风险进行了评估。结果表明:不同类型作物生产所面临的风险大小不同,单产损失风险从大到小依次为大豆、玉米、水稻;西北部地区县域的风险普遍较大,其次是东南角地区,而中部地区县域的风险相对较小;吉林省玉米、水稻和大豆3种作物单产损失率30%以上的概率较小。

青海省农作物种植结构和产量变化及秸秆资源估算

本研究基于统计数据,分析了青海省2000-2018年的农作物种植面积、产量及秸秆资源量的变化规律及结构组成。结果表明:青海省农作物以粮食和经济作物为主,占总播种面积的83%-93%。近年来经济作物占比降低,蔬菜类及饲料作物占比逐渐增加。粮食和油料作物总产量在1.00×10^(9)kg和2.85×10^(8)kg左右,单产分别为3.65×10^(3)kg/hm^(2)和1.80×10^(3)kg/hm^(2)左右,粮食和油料作物总产量增加主要得益于单产的提高。蔬菜类的产量和单产分别在1.50×10^(9)kg和3.44×10^(4)kg/hm^(2)左右,其总产量增加主要得益于播种面积的扩大。青海省农作物秸秆总量在1.36×10^(9)kg-1.85×10^(9)kg范围变化,小麦和油菜秸秆占总量的53%。青海省粮经作物播种面积下降,其单产继续提升的空间有限,蔬菜类单产仍有较大提升空间,小麦和油菜秸秆资源利用潜力最大。

The assessment of soil loss by water erosion in China

Soil erosion is a major environmental problem in China.Planning for soil erosion control requires accurate soil erosion rate and spatial distribution information.The aim of this article is to present the methods and results of the national soil erosion survey of China completed in 2011.A multi-stage,unequal probability,systematic area sampling method was employed.A total of 32,948 sample units,which were either 0.2-3 km2 small catchments or 1 km2 grids,were investigated on site.Soil erosion rates were calculated with the Chinese Soil Loss Equation in 10 m by 10 m grids for each sample unit,along with the area of soil loss exceeding the soil loss tolerance and the proportion of area in excess of soil loss tolerance relative to the total land area of the sample units.Maps were created by using a spatial interpolation method at national,river basin,and provincial scales.Results showed that the calculated average soil erosion rate was 5 t ha-1 yr-1 in China,and was 18.2 t ha-1 yr-1 for sloped,cultivated cropland.Intensive soil erosion occurred on cropland,overgrazing grassland,and sparsely forested land.The proportions of soil loss tolerance exceedance areas of sample units were interpolated through the country in 250 m grids.The national average ratio was 13.5%,which represents the area of land in China that requires the implementation of soil conservation practices.These survey results and the maps provide the basic information for national conservation planning and policymaking.

我国农作物灾害性损失风险的估计:方法选择与改进

精准估计农作物灾害性损失风险是农业保险开展的基础和前提。本文在比较现有估计方法的基础上,提出了非参数局部线性加权估计方法并进行了数值仿真模拟,结果表明:现有方法受模型设定或参数选择的影响较大且估计结果不同程度地偏离真实数据,改进方法则克服了模型设定和参数选择问题且估计误差低于现有方法。基于1950~2014年粮食单产数据的估计结果表明,相对于改进方法而言现有方法低估了农作物灾害性风险。该研究对丰富农作物灾害损失风险估计方法,加快农业保险供给侧改革,促进农业保险可持续发展具有重要意义。