Nutrient Losses from Sloping Lands as Affected by Surface Mulching and Cultivation in Sichuan

IPNI-2009-CHN-SC17

14 Jan 2013

2012 Annual Interpretive Summary

Maize Yield and Nutrient Losses from Sloping Lands as Affected by Different Rates of Nitrogen, Phosphorus and Potassium Fertilizers in Sichuan, 2012

The objective of this project was to evaluate the effect of application of different rates of N, P and K fertilizers on maize yield and nutrient losses from Sichuan's sloping farmlands during the summer rainy season. Treatments consisted of six rates of N (0, 225, 300, 375, 450, 600 kg N/ha), three rates of P (0, 150, 300 kg P2O5/ha), and two rates of K (0 and 150 kg K2O/ha) with three replicates and a plot size of 8 m2. Nitrogen was used as urea (N 46%), P as mono-ammonium phosphate (N 11 % and P2O5 44%), and K as KCl (K2O 60 %). Nitrogen was split applied at seeding, seedling, elongation, and tasseling stages in 10:20:20:50 ratio, respectively, while P and K fertilizers were applied in full at seeding.

Results showed the application of 225-150-150 kg N-P2O5-K2O/ha, respectively, as the optimal fertilization strategy, which produced the highest maize kernel yield. These results were in agreement with previous year results. Once N rates were above or below 225 kg N/ha, the maize yields dropped. All the NPK treatments considerably reduced water runoff when compared with N, P, or K omission treatments. The reduction in runoff ranged from 16 to 24% due to applied N, -2.4 to 18% due to applied P, and 16% due to applied K. Soil erosion, however, reduced from 13 to 37% in three N rate treatments (225, 300 and 375 kg/ha), from -30 to 21% in two P treatments (150 and 300 kg P2O5/ha), and 24% in the K treatment (150 kg K2O/ha) when compared with N, P or K omission treatments. The increased soil erosion in treatments receiving higher N rates was probably due to poor crop growth (about 16% reduction in biomass), thereby, decreasing the soil cover and increasing the impact on soil particles from direct rain drops. Losses of N through water runoff increased significantly with an increase in N rates, while loss of P and K did not change much with increased P rates. The quantity of nutrients lost from the field decreased with advancing maize growing season. The total amounts of nutrients lost during the maize growing season were 10 to 46 kg N, 0.6 to 1.0 kg P, and 4.3 to 8.6 kg K/ha. The results imply that overdose of N (rather than P and K) would impose considerable threat to the environment. Sichuan-BFDP-09