Abstract:

A field experiment was conducted to evaluate the effect of application of liquid Bacillus subtilis micro-fertilizer（BSMF）on nutrient absorption,utilization and fruit quality of citrus at orchard. During two consecutive growing seasons of 2017 and 2018,each plant was applied twice in the late stage of the physiological fruit drop period（June）and fruit expansion period（August）with 200,400,600,800,and 1 000 mL of BSMF solution diluted to 15 L as treatments of BSMF200,BSMF400,BSMF600,BSMF800 and BSMF1000,respectively,and 15 L water for each plant was applied as the control. Soil, leaf,root and fruit samples were collected twice for measuring in late October and late December of the same year. The results showed that the application of BSMF can slow down the decline of P and K content in leaves at the fruit ripening stage by promoting the absorption of available P and K nutrients from soil and the release of soil available P and K,which resulted in maintaining a relatively higher nutrient appropriate level in leaf. At the same time,it not only helps to promote fruit enlargement and increase the weight of single fruit,but also helps to reduce the fruit titratable acidity and improve the solid acid ratio at the fruit mature stage,which makes the fruit bigger and the flavor better. In addition,the fruit juice yield also improved. Considering the cost comprehensively,200 mL · plant^-1 of BSMF can promote the release of soil available P and K nutrients and improve the absorption and utilization of soil moisture and nutrients by citrus plants under the experimental conditions,which resulted in maintaining the higher P and K nutrient levels in the fruit ripening stage,and ultimately improving the fruit quality and yield increase.

Key words: citrus, nutrient absorption, fruit quality, micro-fertilizer, Bacillus subtilis