2007 Volume 6 Issue 2 Pages 189-193
This study confirmed the usefulness of fertigation based on cumulative solar radiation in order to establish a fertigation technique that would decrease the nitrate concentration in spinach leaves (Spinacia oleracea L.). The plant growth, the nitrate concentration, and the nitrate utilization/application ratio was determined using potted plants. When the nitrate concentration in the irrigation water was varied, and the water quantity applied to the plants was varied to equalize the nitrate quantity applied to the plants, the plant fresh weights increased and the nitrate concentrations decreased with increases in the irrigation water. The leaf color, however, turned yellow when the irrigation water was increased. In the next study, the nitrate quantity applied to the plants was simultaneously increased with the irrigation water. Plant growth was promoted without leaf yellowing or nitrate accumulation by applying 1.2 times as much as the standard fertigation. The nitrate utilization/application ratio was about 90%, which is considered very high. In conclusion, fertigation based on cumulative solar radiation was considered effective for supplying water and nutrient in accordance with the plant demand, and this technique was suggested to be effective for spinach production without nitrate accumulation in leaves and NO3-N discharge from the soil.
