Optimum chemical fertilizer N substitution with organic manure N improves nutrient uptake, yield, and quality of muskmelon in Xinjiang

  Objectives  Xinjiang has abundant organic fertilizer resources. We studied the suitable proportion of organic fertilizers to replace chemical fertilizer in Xinjiang, in order to reduce chemical fertilizer input for sustainable production of muskmelon.

  Methods  Field experiments were carried out for two consecutive years in 2016 and 2017, with muskmelon cultivar, Huangpi 9818 as test material. Based on the NPK recommendation for muskmelon in Xinjiang, four organic replacement ratios 100%, 75%, 50%, and 25% (M, MF₁, MF₂, MF₃) were applied, with whole chemical fertilizer as control. The organic fertilizer amount of each treatment was calculated according to its N content, and chemical fertilizers were used to keep the same P and K input in all the treatments. In the main growth period of muskmelon, the biomass and N, P, and K content of aboveground part of muskmelon were measured, and the proportions of periodical accumulation of N, P, K in the whole growth period were calculated, and the yield and soluble solid contents of muskmelon were determined at full maturity.

  Results  Compared with whole chemical fertilizer treatment, organic fertilizer ratio of 100% reduced the NPK periodical and total accumulation, and reduced the melon yield and quality. By substituting 25%–50% of chemical fertilizer, the periodical NPK uptake were not significantly different from those from whole chemical fertilizer treatment, except at the vine stage, while the total N uptake at the mature stage was higher than whole chemical fertilizer treatment. In addition, MF₃ and MF₂ treatments increased the accumulation of N, P, and K from the fruit enlargement stage to full maturity stage and the proportion of nutrient distribution from flowering to mature stage. The melon yield and soluble solid contents of MF₃ and MF₂ treatments were not significantly different compared with those in whole chemical fertilizer treatment while M and MF₁ treatments had comparably lower yield and soluble solid contents in both years.

  Conclusions  In Xinjiang, replacement of chemical fertilizer with up to 75% organic fertilizer does not meet the requirement of NPK uptake and decreases the yield and quality of melon. However, replacing chemical fertilizer with 25%–50% organic fertilizer provides NPK nutrition more suitable for the uptake of muskmelon thereby, improving the yield and quality of muskmelon.