Effects of Different Levels of Nitrogen Fertilizer Application Through Drip Fertigation on Sweet Corn Yield in Japan

Abstract

Japan ranks 14^th on the list of total sweet corn production in the world; however, the ranking decreases to 24^th in terms of yield, which represents the amount of production per hectare. This low production efficiency might be due to the conventional Japanese cultivation method; therefore, we applied drip fertigation systems in open fields to increase the yield of sweet corn. Previous studies have shown that the yield of sweet corn can be increased through drip fertigation and that the key factor is nitrogen; however, information about how sweet corn reacts when receiving excessive nitrogen is limited. Therefore, the purpose of this study was to compare the performance of sweet corn using various levels of nitrogen fertilizer with drip fertigation and determine the optimum amount of nitrogen required to produce the maximum crop yield. Six different nitrogen application levels and three different fertigation frequencies were set: (i) 1.5 kg ha^-1 day^-1, fertigation four times per day (N1); (ii) 15 kg ha^-1 day^-1, fertigation four times per day (N2); (iii) 30 kg ha^-1 day^-1, fertigation four times per day (N3); (iv) 1.5 kg ha^-1 day^-1, fertigation once per day (N1-a); (v) 1.5 kg ha^-1 day^-1, fertigation once per three days (N1-b); (vi) no drip irrigation (rainfed), and 130 kg ha^-1 with local practices using granule fertilizers (Control). The results showed that the yield of sweet corn can be increased 2 to 2.5 times higher than that of conventional rain-fed cultivation practices if plenty of nitrogen fertilizer is applied through drip fertigation. The results also indicated that the yield reached a plateau between N2 and N3, so the N3 level of fertilization would cause more harm than good, especially for the environment. The frequency of irrigation was found to be an important factor for yield, especially during the dry season, and crops should be irrigated daily.