NPK fertilization rates and reducing potential in the main citrus producing regions of China

Objectives Clarifying the present situation of N, P₂O₅, K₂O fertilizer input is the base to evaluate the potential of reducing fertilizer application in the main citrus orchards of China.

Methods Field surveys and questionnaires were conducted in the main citrus production areas of China in 2015. The plantation areas, application rate of N, P₂O₅, K₂O fertilizers and the yields of the three main harvested citrus in 2458 households in 9 provinces were obtained, the reducing potential of fertilizer amount was estimated according to the fertilizer recommendation in the open published papers.

Results In the surveyed provinces, the weighted average yield of citrus was 26480 kg/hm², and the overall level of the yield is relatively low. The application rates of N, P₂O₅, K₂O fertilizers were 494, 364 and 397 kg/hm², respectively, with the ratio of 1∶0.74∶0.80. And 99.2% of total surveyed citrus orchards received chemical fertilizers, while only 47.8% received organic manure, merely accounting for 9.58%, 9.6% and 6.24% of total N, P₂O₅, K₂O inputs, meant the organic fertilizer was seriously deficient in citrus orchards. According to the reported fertilizer recommendation for citrus, the excessive applying area of N, P₂O₅, K₂O fertilizer occupied 57.3%, 76.6% and 69.1% of the total citrus area, with excessive amount of 362, 425, and 355 million kilograms, and the corresponding reducing potential of N, P₂O₅, K₂O fertilizers was 28.3%, 48.2% and 29.0%, respectively, the excess proportion of phosphorus fertilizer was the highest, while the N, P₂O₅, K₂O fertilizers excess proportion, amount and reducing potential in orchards in Fujian and Pomelo were all the highest.

Conclusions The average fruit yield per unit area of citrus in China is low, while the excessive application of N, P₂O₅, K₂O fertilizer in citrus orchards is serious with great reducing potentiality, especially that of phosphorous fertilizer. The largest reducing potential is in pomelo production in Fujian provinc, where has the largest area and rate of excessive application of N, P and K fertilizers.