Abstract
The effects of drip fertigation were examined by analyzing the yield and quality of leaf vegetables, and assessing the efficiency of nitrogen (N) fertilization in outdoor plant culture in experimental and farmer fields using water from the Kasumigaura irrigation system. 1) Compared with the results from conventional cultivation, yield of spring Chinese cabbage increased with drip fertigation, even when the N application rate was reduced by 25% from that used in conventional culture. The plant N recovery rate increased by 30% and the rate of N leaching into subsoil was reduced in comparison with the levels in conventional cultivation. In addition, yield and quality of autumn lettuce were maintained, even when the N application rate was reduced by 47% from that used in conventional cultivation. The daily supply of a fixed amount of nutrient solution via the fertigation system, maintained soil moisture at levels greater than those in conventional cultivation; however, small variations were observed. 2) By stopping drip fertigation seven days before harvest, nitrate ion concentrations in spring Chinese cabbage were reduced, while vitamin C and sugar concentrations were increased, suggesting improvements in the quality of the plants' edible parts. The effects of drip fertigation on yield and quality of lettuce were verified by using a fertigation system in a farmer's field. The rate of N utilization by the farmed plants under drip fertigation was twice that under conventional cultivation.
