Abstract
The mechanical har vesting of spinach for processing use is becoming common in Japan. We investigated the effects of cultivars and cultivation conditions, including the supplemental application of fertilizer after first harvesting and the time of first harvesting, on leaf yield and appearance quality in ratoon cropping, which utilizes regrowth of spinach foliage, in Miyazaki Prefecture, which is the largest spinach producing center in Japan. Regarding whole plant weight at harvest, there was no significant difference between cultivars, but the ratio of foliage weight cut at harvest to whole plant weight was consistently higher in the upright cultivar‘ Kuronosu’ than in‘ Sapuraizu7’ in both the first and second cropping (ratoon cropping) with supplemental fertilizer application. In‘ Kuronosu’ cropping, the supplemental fertilizer application after first harvesting increased the foliage weight at the second harvest and percentage of good leaves for products. In addition, the longer growing period increased the foliage weight at the second harvest. Therefore, in a mechanical harvesting system with ratoon cropping, the following measures are recommended: upright cultivars should be grown; when the plant length reaches approximately 40 cm, spinach should be initially harvested to ensure adequate growth period for the second harvesting; and supplemental fertilizer should be applied after first harvesting.
