Evaluation of Nutrient Balance in Soil-Vegetable System using Nutrient Permissible Surplus or Deficit Rate.

Scientific evaluation of nutrient balance in soil-crop systems is very helpful for improving soil fertility management. Nutrient balance in a soil-vegetable system in a vegetable production area of 55 ha was evaluated using nutrient permissible surplus or deficit rate. The study area consisted of 182 farmer plots belonging to six production groups. A total of 217 soil samples from the 0- to 20-cm depth were collected on a 50×50-m grid in the study area before the first crop seeding. Prior to the first crop harvest and the next crop harvest, respectively, vegetable yields were determined and vegetable samples were collected at sites corresponding to the soil sampling locations. The information on fertilizer use such as varieties, rotations, chemical fertilizer and organic manure use, and vegetable yield was surveyed for all farmer plots. The results indicated that significant surpluses of nitrogen (N), phosphorus (P2O5), and potassium (K2O) in the soil-vegetable system were observed, with an average of 314.5, 236.1, and 103.4 kg/ha.a, respectively. Nitrogen practical surplus rates was 46.3%, 35.2 percentage points higher than N permissible surplus rates of 11.1%, indicating that excessive N fertilizer was applied in the vegetable production area. Phosphorus practical surplus rates (255.8%) were 256.7 percentage points higher than P2O5 permissible deficit rates (-0.9%). Phosphorus surpluses in the vegetable production area greatly exceeded its rational range. Potassium practical surplus rates (44.6%) were 87.1 percentage points higher than its permissible deficit rates (-42.5%). Application of K fertilizer in the study area should be improved by balanced fertilization to rationalize soil K status. [ABSTRACT FROM AUTHOR]