Spatial characteristics of soil available nutrients in farmland at a county scale in Weihe Plain, China

Soil available nutrients serve as reliable indicators for evaluating soil fertility. The complete understanding of soil available nutrients is the foundation of soil nutrient management and reasonable fertilization. This study targeted at Xingping County and explored the spatial and temporal patterns of soil available N, P and K in Weihe Plain farmland, using GIS technology and data from 3414 experiments. Our objective is to provide scientific guidance and theoretical basis for the regional balanced fertilization, farmland maintenance and agricultural production. The results showed that the current average contents of soil available nitrogen (AN), available phosphorus (AP) and available potassium (AK) in Xingping farmland were 38.38 mg·kg-1, 27.13 mg·kg-1 and 202.07 mg·kg-1, and the average ratio of AN to AP (N/P) was 1.99. These three nutrients belonged to weak spatial dependence under 400 m sampling scale, mainly affected by fertilization, cropping systems, topography, soil types. As a whole, soil AK was abundant, while 7.43% of AP and 67.98% of AN was lack. During the past 30 years, compared with the results in the 1980s, AN content decreased and its reduction rate increased from east to west and from south to north. AP content increased and its increasing rate increased from south to north. AK content generally increased while increased in the north and decreased in the south. At the same time, soil available N/P ratio in the whole had reverse trend. The blindness of fertilization and low fertilizer utilization rate are the major obstacles. It should be paid close attention to the effective supplement of N fertilizer, the control of P fertilizer and the consumption of soil available K in the southern Weihe terrace, so as to balance soil nutrients and improve the regional economic and ecological benefits.