Analysis on Soil Fertility Obstacle Factors in Eucalyptus Plantations of Different Successive Rotations
Soil fertility and obstacle factors of different successive rotation eucalypt plantations were analyzed to provide data to support improvement of planting and management of eucalypt plantations. Eucalypt plantations (of 1～4 rotations) in Guangxi Paiyangshan Forest Farm were selected as the research objects,with 15 chemical indices such as soil pH,organic matter,macro-nutrients,medium-nutrients and micro-nutrient elements being analysed. The soil obstacle factor diagnosis model was evaluated by the hierarchical clustering method and principal component analyses method. Soil fertility barrier factors in different successive rotations of eucalypt plantation were analyzed. The results showed that with increasing successive rotations of eucalypts,the highest soil fertility obstacle degree was found in the fourth successive rotation,and the higher the soil fertility obstacle degree was,the lower the soil fertility was. The total value of soil fertility obstacle degree was found to follow the order:4th rotation>1st rotation>2nd rotation>3rd rotation. From 60 soil chemical property indices evaluated,28 soil obstacle factors were identified,of which 17 were mild obstacle factors and 11 were severe obstacle factors. The soils' content of total nitrogen and total potassium were obstacle factors in all successive rotations,the contents of organic matter,available nitrogen and available potassium were obstacle factors in the 1st,2nd and 4th rotation plantations,and pH was a severe obstacle factor in the 1st,3rd and 4th rotation plantations. The severe obstacle factors of continuous planting of 1～4 rotations of eucalypts were available iron and pH,total phosphorus,available nitrogen and available potassium,pH,available iron,available nitrogen,total phosphorus,pH and available phosphorus. Successive rotations of eucalypts resulted in the degradation of soil fertility and the reduction of levels of many nutrient elements and medium and minor nutrient elements.
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