Effect of Nitrogen and Molybdenum on Pineapple Yield and Nitrate Concentration in Fruit

Abstract

A study on the effect of nitrogen and molybdenum on yield of pineapple and nitrate concentration in fruit was conducted on Fang Daeng soil in a farmer field at Ronthong subdistrict, Bansapan district, Prachuap Khiri Khan province during 2012-2013. The experimental design was arranged in randomized complete block (RCBD) with nine treatments and four replications. The treatments comprised T1: control with no fertilization, T2: 13-7-35 formula chemical fertilizer at the rate of 50 kg/rai, T3: 13-7-35 formula chemical fertilizer and ammonium sulfate each at the rate of 25 kg/rai, T4: foliar application of 0.5% sodium molybdate (50 g/rai), T5: 13-7-35 formula chemical fertilizer at the rate of 50 kg/rai and foliar application of 0.5% sodium molybdate (50 g/rai), T6: 13-7-35 formula chemical fertilizer and ammonium sulfate each at the rate of 25 kg/rai with foliar application of 0.5% sodium molybdate (50 g/rai), T7: foliar application of 1.0% sodium molybdate (100 g/rai), T8: 13-7-35 formula chemical fertilizer at the rate of 50 kg/rai and foliar application of 1.0% sodium molybdate (100 g/rai), T9: 13-7-35 formula chemical fertilizer and ammonium sulfate each at the rate of 25 kg/rai with foliar application of 1.0% sodium molybdate (100 g/rai). First fertilization was made three months after planting using ammonium sulfate at the rate of 50 kg/rai. At 10 months old, pineapple was artificially induced to flower using calcium carbide and 45 days after that, fertilizers with respect to the treatments were applied. Pineapple was harvested at 18 months of age. Result showed that the use of 13-7-35 formula at the rate of 50 kg/rai together with foliar application of sodium molybdate at 0.5 and 1% concentrations (50 and 100 g/rai, respectively) highly significantly gave the highest pineapple fruit yield of 8.06 (T5) and 8.08 (T8) ton/rai, respectively. The application of 13-7-35 formula chemical fertilizer and ammonium sulfate, each at the rate of 25 kg/rai with or without foliar application of sodium molybdate did not increase pineapple yield. Both rates of sodium molybdate applied foliarly effectively reduced the concentration of nitrate in pineapple fruit. The addition of ammonium sulfate resulted in the increase of nitrate in fruit. The foliar application of sodium molybdate with no plant major nutrient supply gave low yield of pineapple due to the lack of plant major nutrient, molybdenum restraining the uptake of nitrogen and retarding the growth of pineapple. All fertilizers used had no effect on the differences of plant nutrient concentrations in pineapple fruit of which potassium was detected in the highest amount followed by nitrogen and phosphorus, respectively.