Studies On Application Of Controlled-release Fertilizers In Welsh Onion (Allium Fistulosum L.)

The controlled-release fertilizers can control the nutrient release rate, and make the nutrient releasing accordant with plant nutrient absorption. The CRF could improve the use efficiency of fertilizer,increase the content of nutrient in soil, enhance the yield, and improve the quality.To clear the law of the CRF nutrient release, the experiment researched the law of CRF release in water, then, regarding welsh onion of Zhangqiu as test material, studied the effect of CRF on physiology and biochemistry index of welsh onion. Meanwhile, the experiment compared the fertilizer efficiency of CRF and CCF on welsh onion. According to the long growth cycle of welsh onion, the experiment divided into two periods: the seedling stage and colonization stage. The purpose of this study was to solve the problem in welsh onion production, and provide theoretical basis and technical support for the large area popularization and application of CRF on welsh onion. The research results were as follows:1.The nutrient release characteristics of CRFs in water: The release characteristics of nitrogen,phosphorus and potassium illustrated the the law of the CRFS nutrient release in water. The three nutrients release curve of CRF in water showed a shape of"S". Three release stages were found in CRF releasing curve. Release rate increased with time in the first stage,fastigium and decreased with time in the third stage. Compared to CRF1(21-6-15), the release rate of CRF2(15-8-19) was slower. The nitrogen accumulative release rate of two CRFS reached 85% in release stage, and the accumulative release rate of phosphorus and potassium did,t reach 85%, but more than 80%.2. The effects of the CRF on pot seedling of welsh onion: Strong welsh onion seedlings are the basis of stable and high yield. Cultivating strong seedling has significant meaning. Based on the same amount of CRF and CCF, when we used more fertilizer, the CCF would be unfavorable to seedling emergence and damage the welsh onion seedling. When we used less fertilizer, the CCF would be unfavorable to the seedling growth, and the CCF would be lack of nutrient in the growth late stage. However the CRF would not occur these condition. Compared to the CCF, the CRF could improve the quantitative character,such as plant height, stem diameter, seedling index, and enhance the content of chlorophy and soluble sugar.3. The effects of the CRF on welsh onion yield: Welsh onion has long growth cycle, and would need large amount of nutrient. Now vegetable famers input large quanity chemical fertilizer to enhance the welsh onion yield. However it caused severe environmental pollution, and the quality of welsh onion could not be guaranteed. The results showed: when the amount of CRF was the half of the CCF', the CRF still improved the quality of welsh onion, and the yield wuold not decrease. Because the amount of fertilizer was decreased, the cost of CRF was similar to the CCF'. Because the quality was improved, the price of welsh onion would be improved ,so we would get higher economic value. The CRF could make the plant increasing rate reach 38%-47%, and the CCF could make the plant increasing rate reach about 30%.4. The effects of the CRF on welsh onion quality: Different fertilizers have different effects on welsh onion quality, and the CRF could improve the welsh onion quality obviously. The results showed that: Compared to CCF, the CRF could enhance the content of chlorophy, soluble sugar, soluble protein and Vc. The amount of CRF at 100g/m2 was the best application rate, and this amount has the most obvious improving effect on welsh onion quality. At this application rate, the quality indexs were higher than the other CRF treatments and the CCF treatments. It showed the CRF also need suitable nutrient ratio.5. The effects of the CRF on welsh onion nutrient: The CRF could offer nutrient sustainedly, and this made the content of nutrient in welsh onion can be followed. Whether in seedling period or colonization period, the content of total nitrogen in welsh onion was the highest, and the content of total phosphorus was the lowest ,and the content of total potassium was between the nitrogen'and the phosphorus'. The content of nutrient inside plant not only reflect the absorptive capacity of welsh onion, but also reflect the supply capacity of soil, so we could ensure the fertilizer efficiency. The research results showed the nitrogen efficiency of CRF could reach 40%-56%, but the nitrogen efficiency of CCF was only 20%-30%. The CRFs could improve the use efficiency of fertilizer significantly.6. The effects of the CRF on soil nutrient: The CRF could enhance the content of organic matter, alkali-relesed nitrogen, available phosphorus and available potassium in soil.And the CRF could make the soil maintain higher amount of available nutrient, so it would be beneficial to the growth and development of plant.Because the CRF could control the nutrient release rate, after applying CRF, there's less chance for the nutrient highly centralized to form microzone point. Compared to the CCF, the CRF has greater effects on the available nutrient in the soil. The research results showed the nutrients which the CCF supplied have great variational amplitude, and this could not guarantee the sustained and more nutrient in the soil. But the CRF could maintain more nutrient in the soil to meet the growth demand of welsh onion.