Tomato Cultivation by Placing Controlled-release Fertilizers on the Wick in the Root-proof Capillary Watering System

Abstract

The ‘packed bag-fertilization’ method of controlled-release fertilizer for tomato cultivation was investigated using a root-proof capillary wick watering system. This method facilitates removal of residual fertilizer before the soil is reused. The granules of fertilizer were packed in a water-permeable bag, which was placed on a wick in the soil. In this experiment, packed fertilizer (PF) was compared with mixed fertilizer (MF). Medium-fruited type of tomato plants were grown for 132 days from September to February up to the 7^th truss. There was no difference between PF and MF in plant height, whereas stem diameter at decapitation was smaller in PF than in MF. Fruit yield per plant was 2.1 kg in PF and 2.4 kg in MF. At the end of the experiment, the fertilizer bag was removed from the soil and analyzed. Elution percentages of total-N, P₂O₅, K₂O, CaO and MgO were 60, 40, 50, 50 and 30, respectively. The nutrients in soil after removing the bag were also analyzed. There was no increase in the concentration of any nutrient components during cultivation, indicating that there was no nutrient enrichment in the soil, although the amount of total-N in MF soil increased. Therefore, the soil used in PF has high reusability. The total amounts of nutrient decrease in soil were smaller in PF than in MF. It seems that the low vegetative growth and yield in PF is due to a lower elution rate of fertilizer from the bag. In conclusion, PF should be enhanced the elution rate of fertilizer during the early growth stages in order to improve fruit yield in the later growth stages.