Nutrient Management Strategies for Chongqing

Since the establishment of this monitored village in 2001, researchers have been continuously tracking the effects of different phosphorus (P) and potassium (K) treatments with nitrogen (N) on crop yield. Results will be used to guide fertilizer application for the county, track changes in soil fertility with N and predict sustainability under different nutrient input regimes.

Results in Year 5 find continued improvement in rice grain yield responses to increased rates of P and K. Compared to the - P and - K treatments, yields were 380 kg/ha (+6.3%) and 737 kg/ha (+12.2%) higher with 135 kg P₂O₅/ha and 135 kg K₂O/ha, respectively. Rice yields under zero P input have varied from 8.4 t/ha in 2001 to 5.9 t/ha in 2005. Yields under zero K input varied from 8.0 t/ha in 2001 to 6.0 t/ha in 2005. This yield reduction may also be attributed to the use of different rice varieties each year and the effects of unfavorable weather. In the uplands, the P and K response in corn, wheat, and sweet potato was similar to results in rice, but the latter two crops did require lower P and K rates than rice (i.e., 150-90-90 kg N-P₂O₅-K₂O/ha for wheat and 75-60-120 kg/ha for sweet potato). Annual application of P and K is of great importance to maintain yield and soil fertility. It appears that soil K reserves are being depleted faster than soil P. Chongqing-NMS-05