FERTILIZER APPLICATIONS AFFECT FOLIAR NITROGEN, CHLOROPHYLL, SHOOT GROWTH AND YIELD OF 'QING' CHINESE CHESTNUT

Three different fertilizer treatments were applied in 2005 and 2006 at equivalent annual rates of nitrogen to determine their effect on growth and yield of ‘Qing’ Chinese chestnut trees. Chlorophyll meter readings were also obtained to determine their relationship to foliar nitrogen. The fertilizer treatments were: 1) 150 kg N/ha in the form of slow–release fertilizer (Pro-Grow) applied on 1 Mar.; 2) 75 kg N/ha in the form of NH₄NO₃ applied on 1 Apr. and on 15 June; and 3) 75 kg N/ha applied on 1 Apr., 30 kg N/ha applied on 15 June, and 45 kg N/ha applied on 10 Oct. all in the form of NH₄NO₃. ‘Qing’ trees treated with two applications of NH₄NO₃ resulted in greater yield and less terminal shoot growth than other fertilizer treatments in 2005. In 2006, yield was similar, but nut growth may have been influenced by adverse weather conditions. The SPAD-502 chlorophyll meter readings had the strongest relationship to foliar nitrogen when mid-shoot leaves from current season’s growth were sampled in mid-June in both years. Thus, the SPAD meter may be a promising tool for the rapid assessment of foliar nitrogen of ‘Qing’ Chinese chestnut trees and for the diagnosis of nitrogen deficiency.