Suitable water and fertilizer amount for mature jujube with drip-irrigation under fertigation in southern Xinjiang sandy area

Abstract: In order to evaluate the effects of different levels of water and fertilizer on yield and quality of jujube under drip irrigation that changed from flooding, a field experiment was conducted to find the optimal irrigation and fertilizer combination with the higher water and fertilizer use efficiency. The statistical analysis methods of multivariate quadratic regression and normalization were used in this paper. The local jujube variety of Jun-jujube(9 years) was chosen for test material. The conventional flooding irrigation with irrigation and fertilizer quota as 1100 mm and 900 kg/hm2 (N:P:K = 2:1:1.5) respectively was selected as the control group (CK). In this study, the irrigation and fertilizer treatments were designed with a two-factor and three-level quadratic orthogonal rotated composite experiment. The irrigation amount treatments in three levels was W1 (45% CK), W2 (65% CK), W3 (85% CK), and fertilizer treatments in three levels was F1 (45% CK), F2 (65% CK), F3 (85% CK), respectively. The results showed that the effects of irrigation on soil nutrients (total N, available P, available K) and irrigation water use efficiency (iWUE) reached significant level (P < 0.05) in the jujube growth period of flowering and swelling. The effects of fertilization on soil nutrient and fertilizer partial productivity (PFP) reached significant level (P < 0.05) in the period of jujube flowering and swelling. However, the interaction effects of irrigation and fertilization on soil nutrients, yield and jujube quality indicators reached significant level (P < 0.05) at the whole stages of growth. The soil nutrients in 0-40 cm layer were higher under flooding irrigation than that under drip irrigation. There was a nutrient transition layer at depth of 40~60 cm. while the soil nutrients were significantly lower under flooding irrigation than that of drip irrigation in the soil layer of 60-100 cm. The W2F3 treatment had the better soil nutrient environment in the root zone for the different irrigation and fertilizer treatments. Comparing with flooding irrigation, the maximum soil nutrients value under the drip irrigation were W2F3 treatment generally. The drip irrigation treatment of W2F3 had the highest yield, but there was no significant difference with CK (P > 0.05). The maximum value of iWUE and PFP was W1F3 and W3F1 treatment, respectively. The maximum value of total sugar, vitamin C and total acid was in W2F2, W3F3 and W3F1 treatment, respectively. W3F2 treatment and CK had significant difference (P < 0.05) in the net income, and increased by 1.95% comparing with the CK. The mathematic model of water-fertilizer investment and jujube indicators was established through multiple quadratic regression analysis, and the suitable investment of water and fertilizer obtained from the mathematic model were ranged in 651~806 mm and 708~806 kg/hm2, respectively, where N (311-345 kg/hm2), P2O5 (156-178 kg/hm2), K2O (233-267 kg/hm2). The study can provide a reference for the optimal irrigation and fertilization management of jujube cultivation in the southern Xinjiang sandy area with drip irrigation.