Effects of water soluble NPK fertilizer with different content of alginate on apple growth, quality and rhizospheric soil nutrients

Abstract:【Objective】The effects of alginate water soluble fertilizer on apple growth, yield, quality, nutrient absorption and rhizospheric soil nutrient were studied to provide a theoretical basis for rational application of water soluble fertilizer with alginate in apple orchard.【Methods】A 2-year positioning experiment was carried out in the apple orchard of Yandianzhuang, Yuanyang County, Xinxiang. The apple variety Starkrimson was used as experimental material, and five treatments were set as follows: NPK (C) (conventional fertilization), NPK (F) (traditional water soluble fertilizer), NPK (HF) (alginate water soluble fertilizer), 3/4 NPK (HF) (25% reduction of alginate in water soluble fertilizer) and 1/2 NPK (HF) (50% reduction of alginate in water soluble fertilizer). In this experiment, the growth, fruit quality, nutrient content, and rhizospheric nutrient of apples under different treatments were measured to explore the potential of alginate mixed with water soluble fertilizer on increasing the efficiency of fer-tilization in apple orchard. All treatments were randomly arranged with three replicates, and the fertilizers were applied in the bud break stage, the first fruit expansion stage, the second fruit expansion stage, and early fruit picking stage, respectively. Field management measures were consistent with the local traditional management.【Results】Apple yield, fresh weight of 100 leave sand area of leaf were increased by the 3/4 NPK (HF) treatment by 20.74% and 101.20% in two consecutive years, compared with NPK (C) treatment, respectively. Compared with the NPK (C) treatment, the soluble solid and solid acid ratio of fruits were increased, and titratable acid content was decreased by the alginate water soluble fertilizer in 2017. There was no significant difference in fruit quality between the treatment of NPK (C) and 3/4 NPK (HF), however, the 1/2 NPK (HF) treatment significantly increased the titratable acid, and reduced the solid /acid ratio, resulting in lower fruit quality in 2018. In terms of fruit color, the hue angle of the 3/4 NPK (HF) treatment and 1/2 NPK (HF) treatment were lower than that of the other treatments in the two consecutive years, which was significantly reduced by 20.50% and 38.66% in 2018 compared with NPK (HF) treatment, respectively. Compared with NPK (C) treatment, the NPK (HF) treatment increased the leaf phosphorus contents in the two consecutive years, although the increase was not significant in 2017. In addition, there was no significant effect on the content of nitrogen in the leaves by reducing the amount of alginate in the water soluble fertilizer in the two consecutive years, and the treatment of 3/4 NPK (HF) could promote the absorption and increase of the contents of phosphorus and potassium in the second year. The NPK (HF) treatment could increase the contents of nitrogen and potassium in the fruits compared with the NPK (C) treatment. The nitrogen content of the fruits under NPK (HF) treatment in 2018 significantly increased by 33.97%. In the treatments of alginate water soluble fertilizer, the fruit nitrogen content in 3/4 NPK (HF) treatment significantly decreased by 28.9% compared with the NPK (HF) treatment in 2017, and the fruit potassium content significantly increased by 13.08% . While in 2018, the fruit nitrogen content of 3/4 NPK (HF) treatment significantly increased by 37.6%, and there was no significant difference in the contents of phosphorus and potassium in the fruits. The treatments of 3/4 NPK (HF) and 1/2 NPK (HF) could increase the ammonium nitrogen contents in the soil layer for two consecutive years, especially in depth of 0-20 cm, the contents of the ammonium nitrogen contents were increased significantly. Moreover, in the soil layer of 0-20 cm, the contents of available phosphorus and available potassium of 3/4 NPK (HF) and 1/2 NPK (HF) treatments were higher than those of the NPK (C) treatment. The principal component analysis showed that the total effect of 3/4 NPK (HF) treatment was the best in the two consecutive year.【Conclusion】Under the current conditions of apple orchard, the 3/4 NPK (HF) treatment in the two consecutive years could increase the fresh weight of 100 leaves and fruit yield, leaf nitrogen content and soil ammonium nitrogen, and improve the fruit quality and color. While the soluble solid of apples of the 1/2 NPK (HF) treatment in two consecutive years were lower than that of the NPK (HF) and 3/4 NPK (HF) treatments. Comprehensive analysis showed that the total effect of 3/4 NPK (HF) treatments was the best.