Improvement of Inorganic Nitrogen Condition by Summer Pruning and Fertilization in ‘Muscat of Alexandria’ Grape Vines under Early Forcing Culture

Abstract

We examined the effects of summer fertilization and pruning on nitrogen levels in the bleeding sap and petioles of ‘Muscat of Alexandria’ grape vines under forcing culture from December. In the summer of 1999, 9 vines under soilless-culture were treated with combinations of 3 different fertilization levels with 3 pruning procedures. The effects of the summer fertilization and pruning on inorganic nitrogen levels in the bleeding sap were not clear. The summer fertilization affected the nitrate nitrogen levels in the petioles at the berry set stage in the subsequent season, since the levels of nitrate nitrogen in 10 gN·m⁻² (10 g nitrogen application·m⁻²) and 15 gN·m⁻² were higher than that in 5 gN·m⁻² in the previous summer. The effect of summer fertilization on the inorganic nitrogen level was marked in the berry set stage; however, the difference in nitrogen levels among the fertilization treatments became indistinct at veraison. The summer pruning also affected the nitrogen levels in the petioles, since the levels of nitrogen in the vines pruned the previous summer were higher than the levels in those that did not undergo summer pruning. However, the severity of winter pruning did not affect the nitrogen levels in the petioles at any of the sampling times.