The effect of nitrogen (N), phosphorus (P), and potassium (K) supply on the growth and nutrient uptake of intermediate-day onions (Allium cepa L.) was investigated in a double cropping system of rice and onion in which rice straw had been annually applied. The experiment consisted of three sets of treatments: N (0, 120, 240, 360 kg·ha−1 N), P (0, 18, 35, 52 kg·ha−1), and K (0, 67, 133, 200 kg·ha−1) with the addition of 8.0 t·ha−1 of decomposed pig manure. The rice straw was incorporated with tillage after harvest. Foliage weight of the onion plant was affected by N rate on 21 Apr. and on 23 May. Bulb weight was also influenced by N rate on 23 May and at harvest. The only difference (P ≤ 0.05) in onion yield was observed between the zero N rate and all the other N levels. Soil pH was correlated with rate of N fertilization. Soil NO3-N for 240 and 360 kg·ha−1 N rates ranged from 36.6 to 113.7 and 49.9 to 148.6 mg·kg−1, respectively, which was at least twice as high as that at 120 kg·ha−1 N rate. The highest fertilizer use efficiency of nitrogen was 36.0% at 120 kg·ha−1 followed by 240 kg·ha−1 at 28.0% and 360 kg·ha−1 at 20.6%. There was no clear effect of P or K rates on P or K concentration in the onion bulbs. K concentration and uptake in the onion leaf tissue increased with higher K rates. In conclusion, compost and rice straw provided sufficient P and K to grow onions without additional P and K fertilizer, and under these conditions, the fertilizer level of 120 kg·ha−1 N produced as much onion bulb yield as higher N levels.
This study was carried out to evaluate the effect of antibrowning agents on browning and storage quality of the peeled shallot bulb. Five kinds of antibrowning agents were used under two different storage temperatures. The agents consisted of 1% ascorbic acid, 2% citric acid, 2% NaCl, green tea extract (17 °Bx) and duo clean (a commercial product). The peeled shallot receiving the agent treatment, was packed into 150±10g sized boxes and closed with polypropylene film. the boxes were stored at a room temperature and 10℃ for 12 days, respectively. The weight loss of shallot bulbs was lower in 10℃ storage than in room temperature storage. In a visual test of bulb freshness, The bulbs in 10℃ storage showed better visual freshness than in the room temperature. 2% citric acid was the most effective antibrowing agents in bulb rot loss and freshness among the antibrowning agents. In addition, the bulbs receiving 2% citric acid had the lowest degree of browning and the highest value of bulb firmness. The combination of 2% citric acid treatment and 10℃ storage should be effective to sustain the storage quality of the peeled shallot.
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