Effects Of Water,Fertilizer And Heat Coupling On Growth,Photosynthesis And Yield Of Custard Apple Under Drip Irrigation

Custard Apple is a tropical fruit with high nutritional value and economic value.It has good natural conditions to popularize and grow in Yunnan.Because the growth of custard apple is greatly affected by the soil environment,most of the growers have less experience in planting custard apple,and there is blindness and experience in the decision-making of irrigation and fertilization,resulting in the yield,quality and economic benefits of custard apple can not reach the expectations.By studying the climate and soil conditions in Yuanjiang,orthogonal experiments of three factors,irrigation amount,fertilizer application amount and irrigation temperature,were set in2021 and 2022 respectively to study the effects of the coupling of water and fertilizer and heat on soil environment,growth and physiological conditions,yield,quality,economic and ecological benefits of custard apple root system.To explore the optimal scheme for irrigation and fertilization in the dry-hot valley area of Yuanjiang,and provide theoretical reference for custard apple growers.（1）In 2021,5-year custard apple was selected,and the three levels of water,fertilizer and heat were set as:irrigation amount（W₁:70%ET_c;W₂:85%ET_c;W₃:100%ET_c）,fertilizer application amount（F₁:1200g/plant;F₂:1350g/plant;F₃:1500g/plant）,irrigation temperature（T₁:15℃;T₂:20℃;T₃:25℃）.The results showed that the soil temperature decreased with the increase of irrigation amount and the decrease of irrigation temperature.The contents of soil nutrients（nitrate nitrogen,available phosphorus,available potassium）increased with the increase of irrigation amount and fertilizer amount.The number of soil fungi increased with the increase of irrigation amount,fertilizer application amount and irrigation temperature.Increasing irrigation amount,fertilizer amount and reducing irrigation temperature could promote the growth and photosynthesis of custard apple.The three factors of water,fertilizer and heat had positive effects on single fruit yield,average single fruit weight,fruit transverse diameter,fruit longitudinal diameter,vitamin C,total soluble sugar and soluble solid,but had weakening effect on organic acid content.The coupling of water and fertilizer with heat affected the economic benefit of custard apple by affecting its quality and yield,and the planting profit increased with the increase of yield and the proportion of medium grade and above fruit.The total cost increases with the increase of production and consumption of water,fertilizer and electricity resources.（2）A new 5-year custard apple was selected in 2022.According to the test results in 2021,the range between the levels of each factor was reduced,and the fertilizer with a higher proportion of nitrogen fertilizer was replaced.The three levels of the three factors of water,fertilizer and heat were set as:irrigation amount（W₄:85%ET_c;W₅:90%ET_c;W₆:95%ET_c）,fertilizer application rate（F₄:1350g/plant;F₅:1400g/plant;F₆:1450g/plant）,irrigation temperature（T₄:18℃;T₅:20℃;T₆:22℃）.The test results show that compared with 2021,the yield increases by 8.25%on average and the profit increases by 6.63%.By comparing the rate of profit improvement with the rate of water and fertilizer resource consumption,it is found that increasing the profit by2.4%will consume 10.53%more water resources and 3.64%more fertilizer.To sum up:the most ecological benefits of water-fertilizer thermal coupling irrigation scheme are 85%irrigation water ET_c,1350g fertilizer application per plant,irrigation temperature 18℃.The optimal short-term economic benefits of the water and fertilizer coupling irrigation scheme were 100%ET_c,1400g/plant fertilizer application and 18℃irrigation temperature.