Nutrient Management Strategies for Yunnan

Qujing County and Songmin County are representative of the grain/tobacco farming system. They were selected to track nutrient variability and collect fertilizer use information and field trial data, all of which will be used to develop a rational fertilizer nutrient management system. Soil deficiencies were determined by soil testing (2001) and village maps of nutrient variability were formed in 2002. In 2003, the objective was to further verify prescribed fertilizer rates and determine nutrient balances for two major cropping systems.

1) Wheat-tobacco at Qujing: The optimal fertilization rate for nitrogen (N), phosphorus (P), and potassium (K) for tobacco was 135-150-135 kg N-P₂O₅-K₂O/ha, using a 1:3 ratio of potassium chloride (KCl):potassium sulfate (K₂SO₄). The optimal rate for wheat was 150-150-225 kg/ha. Tobacco yield increased by 531 kg/ha (37%) compared to the - K treatment and by 560 kg/ha (39%) compared to the - P treatment. Similarly, wheat yield increased by 2,173 kg/ha (60%) compared to the - K treatment and by 2,329 kg/ha (67%) compared to the - P treatment.

2) Broadbean-rice at Songmin: The best treatments were 120-135-300 kg/ha for rice and 39-195-135 kg/ha for broad bean. Rice yield increased by 3,994 kg/ha (48%) compared to the low K (150 kg K₂O/ha) treatment. Similarly, broad bean yield was increased by 1,200 kg/ha (35%) compared to farmers’ practice (135 kg P₂O₅/ha).

Omission of P or K not only significantly reduced crop yield, but also resulted in soil nutrient deficits. Improvements to soil P and K status were noted under the optimal fertilizer rate treatment. Computer software was developed to construct fertilizer recommendations and to serve as a knowledge database for technicians and policy-makers. Yunnan-NMS01