Objectives The effects of adding different ratios of seaweed extracts (60% seaweed extract, 6.5% alginic acid, 5% humic acid, pH 6.7, and 1.15 g/mL density) to NPK fertilizer were studied for the efficient use of seaweed extract.
Methods Peach cultivar of ‘Zhongtao 8’ was used as the test material in a two-year field experiment. The tested application dosages of seaweed extracts were designed as the ratio of NPK fertilizer used in four topdressings (w/w): 0% (CK), 5% (T1), 10% (T2), 20% (T3), and 40% (T4). The seaweed extracts were applied to the soil with NKP fertilizer simultaneously. We measured the single fruit weight, yield, fruit quality, color, and nutrient content of peach.
Results With increasing of seaweed extract dosage, peach yield and quality increased first and then decreased. The highest yield and soluble solid content were recorded in T2 in 2019 and 2020, with 31.77%, 40.67% for yield and 10.67%, 7.20% for soluble solid content higher than CK. Further, the yield of T2 was (P < 0.05) different from other treatments. However, the titratable acid content of T2 was the lowest, which was 11.11% and 50.00% lower than CK in 2019 and 2020. In 2019, except for the soluble sugar in T1, the soluble sugar content and sugar to acid ratio in all the other seaweed extract treatments were lower than CK. Except for T4 in 2020, the soluble sugar content and sugar to acid ratio in other seaweed extract treatments were higher than CK, and T2 was 20.55% and 166.29% higher than CK. Seaweed extract application promoted nutrient absorption and fruit coloring in 2019 and 2020. The highest fruit K content was 16.7% (T2) and 11.94% (T3) higher than CK in 2019 and 2020. Based on the principal component analysis, the total score of T2 was the highest in the two consecutive years.
Conclusions Seaweed extract shows a satisfactory effect in increasing peach fruit yield and quality while improving fruit coloration. The appropriate application dosage of seaweed extracts is 10% of topdressed NPK fertilizer.
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