Legume Green Manuring Improves Soil Fertility and Plant Growth of Eucalyptus Plantation in South Subtropical China

Legume green manure is extensively planted to improve soil fertility in crop field. However, the application of legume in Eucalyptus plantation is still limited and depends on site specific and species. Therefore, the objective of this study was to determine the effects of green manure interplantation on soil fertility and plant growth of Eucalyptus plantation in a short term. A field experiment of one year was established to investigate the green manure growth, forest soil nutrients and Eucalyptus plant growth inter-planted with two legume species (Tephrosia candida, TC and Sesbania cannabina, SC) at south subtropical China. Legumes were inter-planted in linear among the tree space of Eucalyptus stand. Result showed that the green manure inter-plantation increased soil organic matter by 9.66% of TC and 18.44% of SC. Soil available nitrogen, phosphorus and potassium were improved significantly by the legume treatments as well. The increment of height and diameter at breast height of Eucalyptus during the experiment was significant in legume treatments. Thus, the timber volume increment was improved significantly by 46.81% of TC and 35.47% of SC compared with the control treatment. Therefore, the inter-plantation of legume green manure under the Eucalyptus plantation is effective to improve soil fertility and tree growth. Such a measure is potential and referenced for the sustainable forest management

Structural equation model was used to evaluate the effects of soil chemical environment, fertility and enzyme activity on eucalyptus biomass

This paper aims to reveal the effects of multi-generational succession of eucalyptus on soil fertility, organic structure and biological properties. Soil samples were collected from eucalyptus plantations of different stand ages (5, 11, 17 and 21 years old) in a typical area in south Asia, soil organic fraction structure and content characteristics were investigated using Fourier transform infrared (FTIR), and structural equation modelling (SEM) was used to explore influences of soil fertility, enzyme activity and organic fraction on stand biomass. FTIR analysis showed that 11 infrared absorption peaks existed in the soils of this study area, attributed to silicates, aromatics, carbonate ions, sugars, esters, polysaccharides, aliphatic hydrocarbons and phenolic alcohols. Combined with the results of peak area integration, the content of esters, aromatics and phenolic alcohols was significantly higher in 17- and 21-year-old stand soils than in control soils. The results of SEM showed that organic components were negatively related (p < 0.01) to enzyme activity and biomass, with standardized coefficients of 0.53 and 0.49, respectively. In summary, multi-generation succession of eucalyptus trees can change the structure of soil organic functional group composition and promote the enrichment of aromatic and phenolic alcohol functional groups. Such changes can directly inhibit the increase in eucalyptus biomass and indirectly negatively affect biomass by inhibiting enzyme activity