RESEARCH ON GROWTH RESPONSE OF 0POPULUS DELTOIDES CV. “LUX” TO SITE PREPARATION AND FERTILIZATION

The experiment was conducted on lime concretion fluvo-aquic soil. This soil with clayed texture, compact soil body and low nutrient content is a low productive soil in the North China Plain. 5 Years' trial proved that the site preparation of big pit produced remarkable growth response with 19.8% and 91.8% of increment in D. B. H. and height respectively in the first year after planting; fertilization couldn't significantly increase growth in the first 2 years after planting; but N fertilizer, organic manure and the interaction between N fertilizer and organic manure had the significant and positive effects on the tree growth while the application of P K decreased the growth from the third year to the fifth year after planting. Tree volume in the treatment fertilized with N fertilizer and organic manure was increased by 77%. Treatments N K and N P increased volume by 60% and 58% respectively and produced a high economic benefit, the values of input/output for these 2 treatments were 1:6.22 and 1:3.78 respectively. The integrated benefit of site preparation plus fertilization was remarkable, and 85.1%~88.8% of the benefit was due to available fertilization.