Management of Sloping Lands for Sustainable Agriculture in Sichuan
IPNI-1997-CHN-SC22
15 Jan 2006
2005 Annual Interpretive Summary
Management of Sloping Lands for Minimal Nutrient Run-off in Sichuan, 2005
Previous research has shown alley cropping to be a sound soil conservation strategy for Sichuan's sloping lands. In 2005, research was focused on the effect of alley cropping on soil nutrients losses. Losses of available and total nitrogen (N), phosphorus (P) and potassium (K) in the run-off and sediments were determined after each significant rainfall event. This study will analyze and assess the relative contributions of traditional farming activities and the improved practice of using a cash crop hedgerow+balanced fertilization on non-point environmental pollution.
Nutrient losses were highly correlated with the quantity of rainfall early in the growing season. Nutrient losses were minimal after July and the correlation with rainfall quantity was no longer observed. Compared with farmer practice (FP), total N loss from the improved treatment was 23.3% lower, plant available N losses were 11.4% lower, total P loss (-38.3%), available P loss (-18.4%), total K loss (-38.1%), and available K loss (-25.6%). Most losses occurred as sediments were washed away, but run-off was responsible for significant loss of plant-available forms of nutrients. Absolute amounts of available nutrients lost in run-off during the summer season were 19.7 kg N/ha, 0.6 kg P/ha, and 8.8 kg K/ha for FP and 16.5 kg N/ha, 0.5 kg P/ha and 6.4 kg K/ha for the improved practice. Thus, adoption of this improved method of sloping land management reduced N, P, and K losses by 16.3%, 17%, and 27.3%, respectively.
Data indicate that N is most susceptible to leaching losses and the effect on P is minimal. Several other concurrent trials at two different sites have reached a similar conclusion. Under local farming conditions, with applications of 160-80-140 kg N-P2O5-K2O/ha for wheat and 75-75-80 kg/ha for sweet potato, the amount of nutrients being discharged from sloping lands is minor and cannot be the sole cause for surrounding water eutrophication. Sichuan-12A