Effects of Long-term Application of Bag-controlled Slow-release Fertilizer on the Form and Availability of Phosphorus in Red Soil of Southern China

The insufficient supply of phosphorus is the main problem facing agriculture and forestry production in red soil region of southern China.To investigate whether applying bag-controlled slow-release fertilizer can improve the phosphorus availability and available phosphorus component content,with Gaofeng State-owned Eucalyptus Plantations Forest Farm in Guangxi red soil region as the research object,comparative test of different fertilizer types and fertilizer amount of bag-controlled slow-release fertilizer with conventional fertilization(G1),bag-controlled slow-release fertilizer with reducing fertilization(G2),traditional compound fertilizer(G3),basal fertilizer(G4),and no fertilization(G5)was designed.Soil phosphorus classification method was used to determine the content of phosphorus components in the soil,and redundancy analysis was used to study the effects of components on tree growth.The results showed that:compared with traditional fertilization,bag-controlled slow-release fertilizer significantly increased the contents of AP,Pi,Fe-P and other components in soil;the phosphorus activation coefficients of G2 and G1 were significantly higher than those of the other three treatments,and the order was G2>G1>G4>G5>G3;redundancy analysis showed that PAC and Fe-P had the most significant effect on plant growth among all phosphorus components.The application of bag-controlled slow-release fertilizer in red soil of eucalyptus plantation in southern China could promote the accumulation of phosphorus and increase the phosphorus activity.The mechanism of higher phosphorus use efficiency in bag-controlled slow-release fertilizer was mainly through the sustained phosphorus input and reducing phosphorus immobilization in soil by obstructing the contact of phosphorus with acid soil,to guarantee the phosphorus supply in tree growth process.

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.