Research on nitrogen fertilizer recommendation indicator system establishment using soil tested total N and organic matter in rapeseed

This article attempted to establish rapeseed indicator system of soil testing and nitrogen fertilizer recommendation using the regression function mode through analyzing the nitrogen fertilizer effect, economy N fertilizer applied rate, soil total nitrogen and soil OM based on large data of rapeseed nitrogen fertilizer effect and rate experiments in recent years in Zhejiang province. The mathematic model showed that, soil OM, soil total N and the rapeseed relative yield of N deficiency treatment existed a regression index function with Y=20.157e0.4413X（R2=0.5887**）and Y=10.882e0.045X（R2=0.3365**）, while soil OM, soil total N and the economic rate of nitrogen fertilizer application also existed a regression index function with Y=-314.25LnX +1392.9（R2=0.6896**）and Y=-191.77LnX+427.81（R2=0.314**）.The regression determination coefficient R2 among soil OM, the rapeseed relative yield of N deficiency treatment and the economic rate of nitrogen fertilizer application were above the forecast precision. Soil OM may be an index for soil nitrogen supply ability forecast and economic nitrogen fertilizer recommendation in field rapeseed production. However, soil total nitrogen was not a suitable index for soil nitrogen supply ability forecast and economic nitrogen fertilizer recommendation because regression determination R2 was less than 0.35. The soil testing and N fertilizer recommendation indicator system was constructed for rapeseed planting area in Zhejiang province based on regress equations delimited content range of soil OM and recommendation N fertilizer rate under different N supply level.