Spatial and temporal changes of soil nutrients of spring maize field in the Loess Plateau under conservation tillage
Three kinds of farming measures were adopted,such as no tillage(NT),conventional tillage + straw returning(TS) and conventional tillage(CT),to study the effects of different tillage treatments on soil nutrient content of spring maize field in the Loess Plateau for three consecutive years.The results show that soil organic matter content turns a rising trend under conservation tillage with the growing period,in which the soil organic matter content in arable layer was significantly higher than that under other two treatments;Conservation tillage makes the soil nitrogen enrichment up to the surface of soil;The available phosphorus is increasing slightly under conservation tillage,which is obvious in the harvest time and is significantly different from that under TS and CT treatments;The available potassium under conservation tillage treatment is significantly lower than that under other treatments,but there is an increasing trend.
The value of floodplain lands in agricultural use following channelization and the resulting foregone value of these lands were estimated. The latter estimates were incomplete because of the inability to predict effects on potentially important parameters. Estimated differences provide a threshold for decision-making. Policy implications are discussed.