Effects of nitrogen forms on nitrate accumulation and quality of “Kyoho” grape fruit

In order to explore effects of nitrogen forms on nitrate accumulation and the quality of “Kyoho” grape fruit（Vitis vinifera×V. labrusca cv. Kyoho）, treatments of urea T1(amide-state), nitrate T2(NO-3-N/ NH+4-N=100/0), mixed nitrogen T3, T4, T5(NO-3-N/ NH+4-N=70/30, 50/50, 30/70), ammonium nitrogen T6(NO-3-N/ NH+4-N=0/100)and water CK were used as foliar spray in three times in the grape growing season. The results show that compared with CK, quality of the fruit is improved under the N foliar spray treatment. The amount of total sugar and sugar acid ratio are the highest under the T1 treatments, the next is the mixed-N treatments, and those of the NH+4-N treatment are the lowest. Vc contents of fruit are higher under the mixed-N treatments, of which, the NO-3-N/ NH+4-N=50/50 is the highest, NH+4-N is the lowest. The sequence of anthocyanin content of fruit is NO-3-N＞urea＞mixed-N＞NH+4-N＞CK, and the nitrate concentration of fruit is in the order of NO-3-N ＞mixed-N ＞NH+4-N＞ urea＞ CK, which indicates that NO-3-N is beneficial to fruit growth. The average fruit weight for each treatment is NO-3-N＞mixed-N＞NH+4-N ＞urea＞ CK. To sum up the results, appropriate amounts of nitrate and urea are benefit to the quality of grape.