Effects of long-term fertilization on nutrient variety of soil and plant systems in dry-land of Loess Plateau

Based on 20 years of long-term experiment of applying fertilizer on continuous wheat in dry-land of Loess Plateau.Wheat yield,nutrient uptake and soil nutrient were analyzed in year 2005.The results showed that yield was increased by 25.6% and 48.1% with single application of P and N fertilizer,respectively.The N and P uptake was increased too,but the harvest index was decreased.The combination of N and P could increase yield by 101.3%-302.8% and nutrient uptake significantly.Soil nutrient content in surface soil(020 cm) and the distribution of nutrient in soil layer varied.The combination of N and P was an effective ways to soil fertility management.Total P and available P in soil increased by 8.3%-45.2% and 54.8%-917.8%,respectively.The relation between total P accumulation and the amount of P fertilizer applied was y = 0.002x-0.112,and the relation between available P and the amount of P fertilizer applied was y = 9.6537 ln(x)-35.371.The difference was not that significant in subsoil layer.