关键词: 稻菜轮作, 香蕉园, 氮磷盈余, 硝态氮累积, 海南省

Abstract:

【Objective】 Hainan is the province with a large area of rice-vegetable rotation and banana cultivation in China, but the nitrogen (N) and phosphorus (P) fertilizers input by farmers far exceed the nutrient requirements of crops, which may have a negative impact on Hainan's ecological environment. The aim of this study was to investigate the N and P surpluses, and soil nitrate accumulation in typical cropping systems in Hainan, thus to provide scientific basis for evaluating nutrient losses and their impacts and achieving sustainable nutrient management. 【Method】 In 2021-2022, a typical area for rice-vegetable rotation and banana cultivation in Chengmai, Hainan, was selected as the research area and 20 rice-vegetable rotation plots and 15 banana orchards were identified. The information of chemical and organic fertilizer application, straw returning method and amount of above fields were obtained by real-time record of farmers' agricultural activities, crop biomass and the nutrient content were determined at crop harvest, and other nutrient input include nutrient deposition and biological N fixation were obtained by literature survey. Five banana orchards were selected and soil was collected by soil auger method and nitrate N accumulation was measured in the 0-400 cm soil profile.【Result】 The N and P fertilizer inputs to the rice-vegetable rotation were 1 308 kg N·hm^-2 (975 kg N·hm^-2 of chemical and 333 kg N·hm^-2 of organic fertilizer) and 515 kg P·hm^-2 (385 kg P·hm^-2 of chemical and 130 kg P·hm^-2 of organic fertilizer); the aboveground N and P uptake of the crop were 248 kg N·hm^-2 and 48 kg P·hm^-2; the surplus of N and P in rice and vegetable rotation was 1 196 kg N·hm^-2 and 484 kg P·hm^-2. The N and P fertilizer inputs to banana orchards were 1 340 kg N·hm^-2 (1 293 kg N·hm^-2 of chemical and 47 kg N·hm^-2 of organic fertilizer) and 447 kg P·hm^-2 (442 kg P·hm^-2 of chemical and 5 kg P·hm^-2 of organic fertilizer); the aboveground N and P uptake were 242 kg N·hm^-2 and 23 kg P·hm^-2; the banana N and P surpluses were 1 271 kg N·hm^-2 and 435 kg P·hm^-2. The nitrate-N accumulation in the 0-400 cm soil profile of banana orchards was 1 131 kg N·hm^-2. 【Conclusion】 Excessive application of N and P fertilizers has led to the large nutrient surplus in typical soil-crop systems in Hainan, and large amount of nitrate-N has accumulated in banana orchard in the deep soil layer. Hainan produces typical high-value fruit and vegetables at the cost of large nutrient losses and negative environmental impacts, optimized nutrient management should be implemented to ensure its environmental safety.

Key words: rice-vegetable rotation, banana orchard, nitrogen and phosphorus surpluses, nitrate nitrogen accumulation, Hainan Province