Regrowth Ability of Vegetable Sweet Potato and Nitrogen Application Management

• Main Authors: WEI -TING LIU, 劉威廷
• Other Authors: 朱德民
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/89088146924021467162

博士 === 中興大學 === 農藝學系所 === 95 === Vegetable sweet potato is an important summer-season vegetable in Taiwan. Production management of this crop is similar to the forage grass, newly young shoots are harvested after periodically cutting. Proper production managment is important to maintain regrowth ability and productivity of crops. Vegetable sweet potato, cv TN 71, was used as material and planted in field to conduct a series of experiments, including observations both of regrowth ability and annual cultivating experinments from 2000 to 2001. First of all is to explore the main controlling factors─fertilization and cutting, on the regrowth ability of vegetable sweet potato, and the different growth responses in summer and winter season. Futher, the stable isotope, 15N, were used as a tracer to confirm the results obtained from field experinments. Finally, trials of different dosages of fertilizer, of differrent types of fertilizer, and of comparing with organic fertilizer were carried out to figure out the influences of fertilizer and cutting management on productivity of vegetable sweet potato, and make the suggestion on the proper management method. Growth rate, nitrogen absorption, utilization, and meta- bolism of plants were all higher in summer season. Nitrogen absorbed wouldn’t be accumulated in plant but transfer to young shoot mostly, and support the growth. The high production would be reached by fertilizer application after periodically cutting, which could increase shoot numbers derived from lateral buds. However, different responses would be observed in winter season. Lower growth rate, nitrogen absorption, utilization, and metabolism of plants all caused the less acceleration of regrowth ability by fertilizer application. Then, cutting became the more important factor to accelerate re-allocation of internal nitrogen to supply for regrowth of newly young shoot and growth ability of plant. As increasing level of nitrogen application, increasing production of newly young shoot has been observed, but seriously damage on the physical-chemical characters of soil and nitrate accumulation of shoots were also mesured. Therefore, 21 kg/ha nitrogen would be the better usage of nitrogen level applied as same as recommended by CAES (Chia-Yi Agricultural Experiment Station). In addition, salt accumulation and lower pH after long-term application of ammonium sulphate, wouldn’t be recommended fertilizer used. Calcium ammonium- nitrate and urea would be recommened the better types of nitrogen fertilizer. Yields of newly young shoots after long-term application of organic fertilizer wouldn’t less than that chemical fertilizer was used. Function of conserving soil while using organic fertilizer are better than chemical fertilizer used. It would be suggested that organic fertilizer take the place of chemical fertilizer on the cropping system of vegetable sweet potato.