英语新闻 英语考试 留学英语 TEM英语 CET英语 BEC英语 托福英语 雅思英语 英语作文 英语故事 英语笑话 娱乐英语 行业英语 英语学习 生活英语
工作英语 奥运英语 法律英语 英语口语 英文阅读 写作翻译 词汇语法 专四八级 四级六级 考研英语 职称英语 疯狂英语 英文简历 奥运知识 名人演说
您现在的位置: 3edu教育网 >> 英语角 >> 英语新闻 >> 资讯 >> 正文    3edu教育网,百万资源,完全免费,无需注册,天天更新!

干旱影响美国玉米带作物产量

干旱影响美国玉米带作物产量

分类:资讯   更新:2014/5/7   来源:网络

干旱影响美国玉米带作物产量

North Carolina State University's Roderick Rejesus, associate professor of agricultural and resource economics and a co-author of the Science paper, says that corn and soybean yields show increasing sensitivity to drought, with yields struggling in dry conditions in Iowa, Illinois and Indiana during the 1995 to 2012 study period.
    干旱影响美国玉米带作物产量
    Increasingly harsh drought conditions in the U.S. Midwest's Corn Belt may take a serious toll on corn and soybean yields over the next half-century, according to research published today in the journal Science. Corn yields could drop by 15 to 30 percent, according to the paper's estimates; soybean yield losses would be less severe.
    North Carolina State University's Roderick Rejesus, associate professor of agricultural and resource economics and a co-author of the Science paper, says that corn and soybean yields show increasing sensitivity to drought, with yields struggling in dry conditions in Iowa, Illinois and Indiana during the 1995 to 2012 study period.
    "Yield increases are getting smaller in bad conditions," Rejesus said. "Agronomic and genetic crop improvements over the years help a lot when growing conditions are good, but have little effect when growing conditions are poor, like during droughts."
    U.S. corn and soybeans account for approximately 40 and 35 percent of global production, respectively, making the results important to the world's food supply.
    Using field data over an 18-year period, the researchers point to the effects of vapor pressure deficit (VPD) on corn and soybean yields. VPD includes temperature and humidity measures; extremes at either end of this variable signify drought or too much water for crops. Akin to(同类, 近似) the sweet spot on a baseball bat, the best VPD condition is a value in its middle range.
    Some 29 climate estimates modeled in the paper suggest that VPD will rise significantly over the next 40 years, bringing on more severe drought conditions.
    The researchers ran the same tests using the Palmer Drought Severity Index, another widely used measure capturing nationwide temperature and humidity, and reported similar results. They also ran the same tests for a broader group of Corn Belt states to include South Dakota, Nebraska and Kansas. Those tests confirmed the results found in Iowa, Illinois and Indiana.
    Rejesus adds that crop densities may be one reason for the problem. When plants are placed closer together, he says, it's easier for bad conditions to affect more plants. Crop simulations conducted in the study supported this notion.
    Rejesus says that research into more drought-resistant seeds or other ways of combating sensitivity to drought is necessary because the findings have strong implications throughout the food chain.
    "There are a number of risk management implications for farmers," he said. "Should farmers -- 80 percent of whom already purchase crop insurance -- buy even higher levels of crop insurance? What kinds of safety nets should be in place for farmers, if any? What happens to meat prices when corn yields diminish? There are lots of tradeoffs(权衡) involved in this issue."

| 设为首页 | 加入收藏 | 联系我们 | 版权申明 | 隐私策略 | 关于我们 | 手机3edu | 返回顶部 |