Nutrition Diagnosis And The Adequate Application Of Fertilizers Of Thompson Seedless (Grape Vines)

Foliar Analysis is a helpful tool for the adequate application of fertilizers for fruit trees. Since the early of past century, a lot of researches have done in this field in North America and European countries;and foliar analysis becomes a conventional method to guide the application of fertilizers in many orchards. Foliar analysis is considered providing a means to assess the nutritional status of grape tree. In China, however, this technology is still in the experimental stage. It is known that different cultivars of the same species of grape fruit have different contents of elements in their leaves. Therefore, it is necessary to establish the relationship between the nutrients in leaves and the growth of grape and the application of fertilizers. Field experiments and foliar analysis were carried out to evaluate the changes of nitrogen, phosphorus, potassium, and other nutrients in leaves during the growth of grapes, and to study the effects of the application of N, P. and K fertilizers on the fruit yield and quality of Thomson seedless. The main results showed as followings.(1) The application of N fertilizers significantly increased the length growth of newly-grow branches of 6 year-old grape;and as the increase of N fertilizers, the growth of branches was also improved. Compared to N and P fertilizers, the increase rate of branches by K fertilizer was lower;but K fertilizer increased the proportion of fruit-bearing branches.(2) Linear regression model was used to fit the relationship between the application of N fertilizer and N content in leaves. For 6 year-old grape, the model was y N = 20.446+0.00(?), where y n is the N content in leaves, and N is the rate of N fertilizer. It indicates that annually applying 1 gram of N fertilizer for 6 year-old grape tree, there would be about 0.007 g/kg of N increase in leaves. The application of P fertilizer had a significant effect on P content in petioles.(3) The annual changes of nine kinds of essentially mineral elements in the foliar of Thompson Seedless in research regions were analyzed to determine the adequate sampling time for foliar analysis of grape. The contents of N and K in leaves and petioles decreased as the growth of grape;contrarily, the contents of P in leaves and petioles were increased. The content of N in leaves was higher than that in petioles, and P and K in petioles is higher thanthat in leaves. Compared with petioles, the variation of N, P, and K in leaves was greater. As the growth of grape in one year, the contents of Ca, Mn increased significantly;content of Cu increased slowly;and Mg and Zn remained stable. And there was great variation for Fe in the petiole in the growth period of plant. It was recommended that the adequate sampling time for diagnosing the nutritional status N, P and K of the grape is about fifth weeks after the full blooming, i.e., the time before the fruit enters into the rapid expanding period.(4) The application of N and K fertilizers had significant effects on the growth and fruit yield and quality of grapevines. However, the higher levels of N fertilizer might result in the luxurious growth of the shoots, inducing the over-shading of the grape and low quality of fruit. On the other hand, the grape tree deficient in nitrogen produced lower yields and smaller grains of fruits.