Establishment of low input sustainable grassland agriculture in inner mongolia of China. 1. soil fertility of continuous corn cropping field in stock-holding agriculture area

摘要

Soil type in Inner Mongolia, China is aeolian sandy soil, which is poor in nutrients. Corn cropping, however, is continued more than 10 years in this region. The objective of this study is to examine the relation between continuous corn cropping andsoil fertility, based on nutrient budgets in continuous corn cropping field. We chose 4 corn fields, different in successive periods. Soil samples were taken from each field in May and October, 1998. Corn samples were taken in September, 1998. We analyzed nitrogen (N), phosphors (P), and potassium (K) in soil and in corn samples. Soil fertility was evaluated using data on available phosphorous, inorganic nitrogen, and exchangeable potassium. Nitrogen, P and K contents in whole corn plant were calculated from their contents in each part (ear, stalk, leaf). Application rates of fertilizer N and P were larger than corn uptake. Exceeded P was absorbed on soils in surface layer. In case of K, however, corn uptake exceeded its application rate. Shortage offertilized K should be derived from exchangeable K in soil. Soil fertility was maintained in our study sites. We speculated that long-term fertilizing contributed to increase in soil fertility and made possible to continuous corn cropping in this region.