the wheat-fallow rotation that is common in the dryland regions of the U.S. Great Plains. w Bioregulation of soil fertility. Studies are being conducted to deter- mine whether the sequencing of certain crops could effectively enhance nutrient cycling in soils. Particular emphasis is being put on soil phosphorus. The system involves "accumulator plants," some of them deep-rooted, that can use pnosphorus from "pools" that are not readily available to other plants and from well below the usual soil-root zone. The phosphorus used by the accumulator plants then es chemically and positionally avail- able for uptake by "user plants," thereby reducing the need for phosphorus fertilizer inputs. 16
全文预览
