返回Google圖書搜尋

Crop Yield Response to Fertilizer in the United States

出版	U.S. Department of Agriculture, Economic Research Service, 1968
URL	http://books.google.com.hk/books?id=tSy4MgrKIbIC&hl=&source=gbs_api
EBook	FULL_PUBLIC_DOMAIN

註釋The purpose of the estimates presented here is to supply one basis for current appraisals of the economic position of fertilizer use and to project economic potentials for fertilizer use and crop yields. The estimates show crop yield responses to fertilizer in defined areas. This publication supersedes a 1954 report used as a partial basis for estimating potential yields and fertilizer use levels. Much informal and undocumented work was based on the 1954 estimates, and some research based in part on these estimates has been published. Since 1954, more information on yield response to fertilizer has become available. Also, current estimates permit adaptation to more localized conditions than did those of 1954 which were State averages. Major changes in farm technology have altered the rate of yield response, so that adjustment of the earlier estimates to higher yield levels does not adequately characterize responses that now occur. Hence the decision to develop generalized estimates of yield response by crops and areas within the context of current information and modern farm technology.