Effects of N Fertilization on nitrogen absorption, distribution and utilization of Kyoho grape

In order to study the absorption, distribution and utilization of Nitrogen in Kyoho grape, and to provide the theory basis for rational fertilizer application, the impacts of urea fertilization on Kyoho grape were evaluated at three different developmental stages using the 15N-urea tracer method. It is found that the absorbed ratios of the 15N from the fertilizer to total N (Ndff) in different organs are different under the 15N fertilizing treatments at different stages. The Ndffs in the green shoots and fruits are significantly higher than those of the perennial organs and roots at the budding stage, and the Ndffs in all the tested organs are increased at the swollen stage. Comparatively, The Ndff of the ripened fruits is low, which is only 37.6% of the Ndff in fruits at the swollen stage, while the Ndffs of the mature perennial organs and roots are twice-higher than those at swollen stage. As to distribution of nitrogen, 54.8% of 15N absorbed in the plants is distributed to the leaves, while only 3.6% is assigned to the fruits at the budding stage. The distribution rate of 15N in the fruits is 26% while it is 38% in leaves at the swollen stage. In general, the 15N utilization and distribution in different organs show the same trends at different stages. The utilization of 15N-urea in grapes is increased from the budding and reached the maximum in ripened fruits. Kyoho grape trees absorb 3.76-kg N to produce 1000-kg fruits. In descending order, the nitrogen distribution in the organs is: fruits leaves roots annual shoots stems perennial shoots. Besides, the highest demand and most efficiency utilization of nitrogen are from the fruit swollen stage to fruit mature stage, which suggests that the application of fertilizer in practical production should be appropriately delayed.