Adaptability Evaluation Of Multiple Leguminous Forages In The Lichi Orchard

Litchi(Litchi chinensis Sonn.)is an important subtropical economic fruit tree in Hainan Province.Litchi trees have a long childhood and slow growth rate,with relatively wide spacing between rows.In order to fully utilize the resources and environment of the orchard and seek higher economic and ecological benefits,this study explored the efficient ecological management mode of litchi orchards by planting various leguminous forages such as Desmodium ovalifolium,Centrosema pubescens,Arachis pintoi,Stylosanthes guianensis,and Grona heterocarpos between the litchi trees.The study investigated the effects of different treatments on soil physicochemical properties,soil microbial community structure,litchi tree growth,forage yield and nutrient status,with the aim of selecting suitable and ecologically efficient management modes for young litchi orchards and providing theoretical basis and practical experience for the high-yield and sustainable development of litchi orchards.The results are as follows:1.The experimental results showed that the intercropping of leguminous forage had a significant impact on the soil physicochemical properties primarily in the 0-20 cm soil layer.After 18 months of planting,compared to the control,the total nitrogen content in the intercropping Stylosanthes guianensis and Grona heterocarpos increased significantly by 21.9% and 18.7%,respectively.The intercropping patterns of Grona heterocarpos,Stylosanthes guianensis,Desmodium ovalifolium,Arachis pintoi and Centrosema pubescens showed a respective increase of 80.3%,24.1%,63.0%,22.6%,and 26.2% in total phosphorus content compared to the control.The effective phosphorus content in the intercropping Stylosanthes guianensis,Desmodium ovalifolium,Grona heterocarpos,Arachis pintoi,and Centrosema pubescens increased significantly by 176.5%,280.9%,160.8%,76.2%,and 262.9% compared to the control.The intercropping Stylosanthes guianensis,Desmodium ovalifolium,Arachis pintoi,and Centrosema pubescens showed an increase of 19.4%,10.0%,22.6%,and 4.7%respectively in total potassium content compared to the control.Moreover,the effective phosphorus content in the intercropping Stylosanthes guianensis,Desmodium ovalifolium,Grona heterocarpos,Arachis pintoi,and Centrosema pubescens increased significantly by 176.5%,280.9%,160.8%,76.2%,and 262.9% compared to the control.The organic matter content in the intercropping Stylosanthes guianensis,Desmodium ovalifolium,Grona heterocarpos,Arachis pintoi,and Centrosema pubescens increased by 48.9%,35.5%,28.2%,16.4%,and 20.3% respectively compared to the control.The influence of different treatments on soil p H varied at different time periods.In the 20-40 cm soil layer,nutrient levels in all treatments were generally lower than in the surface soil.Over time,the intercropping Stylosanthes guianensis and Desmodium ovalifolium increased the total nitrogen content in the soil.All treatments significantly increased the ammonium nitrogen content in the soil,while the impact on nitrate nitrogen content was not significant.Different treatments had varying effects on soil total potassium,available potassium,and p H values at different time periods.2.Intercropping with Desmodium ovalifolium,Grona heterocarpos,Arachis pintoi,and Centrosema pubescens in litchi orchards did not result in a significant difference in soil microbial diversity.However,intercropping with Stylosanthes guianensis initially showed a decrease in microbial diversity followed by an increase,which requires further observation.The dominant phyla in all intercropping treatments were Acidobacteriota,Chloroflexi,Proteobacteria,Firmicutes,Actinobacteriota,Crenarchaeota,Bacteroidota,Verrucomicrobia,Myxococcota,Gemmatimonadota,and Nitrospirota.There were only slight changes in the dominant phyla during the different treatments,mainly in their relative abundance.Intercropping litchi with Stylosanthes guianensis significantly increased the relative abundance of Firmicutes,Actinobacteriota,Crenarchaeota,and Bacteroidota.3.For the intercropping patterns in the lychee orchard,the intercropping Stylosanthes guianensis significantly increased the height of lychee trees,with a 17.5%increase compared to the control.The intercropping pattern with Stylosanthes guianensis resulted in a 10.6% increase in the height of lychee trees compared to the control.The intercropping pattern with Grona heterocarpos led to a 6.6% increase in the height of lychee trees compared to the control.The intercropping pattern with Arachis pintoi resulted in a 4.6% increase in the height of lychee trees compared to the control.The intercropping pattern with Centrosema pubescens led to a 10.6% increase in the height of lychee trees compared to the control.Planting Stylosanthes guianensis and Desmodium ovalifolium significantly increased the height and canopy size of lychee trees,but had no significant impact on the trunk thickness.4.The legume grass with the highest yield is the Stylosanthes guianensis,followed by the Desmodium ovalifolium.When considering nutrient levels,Stylosanthes guianensis has a significant advantage over other treatments.Taking into account the promotion of litchi growth,as well as the economic and ecological benefits of the orchard,intercropping with Stylosanthes guianensis is the most beneficial option for young litchi orchards,followed by ovate-leaved Desmodium ovalifolium.