Integrative applications of nitrogen, zinc, and boron to nutrients-deficient soil improves sugar beet productivity and technological sugar contents under semi-arid conditions

Abstract

A 2-yr field experiment (2017/18 and 2018/19) was conducted to study the influence of nitrogen (N) at three levels (190 = N1, 240 = N2, and 290 = N3 kg N ha−1), zinc (Zn) at three levels (0 = Zn0, 3.5 = Zn1, and 7 = Zn2 kg ha−1), and boron (B) at three levels (0 = B0, 1.2 = B1, and 2.4 = B2 kg ha−1) on sugar beet’s morpho-physiological attributes and productivity, technological sugar contents, and N-use efficiency based on root yield (RY-NUE). With the increment of N-fertilization level from N1 to N3 (290 kg ha−1) the root growth parameters, SPAD value, and root, top, biological, gross sugar and extractable sugar yields significantly increased; however, sucrose %, extractable sugar %, and purity % decreased. Zn2 (7 kg ha−1) and B2 (2.4 kg ha−1) significantly exceeded Zn0 and B0, respectively, in root growth, SPAD value, sucrose %, extractable %, yields, RY-NUE, and purity %. Also, significant decrements in impurities occurred (i.e., Na, K, and α-amino-N) along with a loss in sugar % in both seasons. Correlation analysis showed that root yield and root fresh weight had highly significant positive r values with extractable sugar and root yields, respectively. Integration of N3 + Zn2 + B2 improved the growth, SPAD value, sugar yields and their qualities, and RY-NUE of beet in a nutrients-deficient soil under semi-arid conditions.