毛白杨在沙地造林的施肥量及其配比（Ⅱ）

研究毛白杨在沙地造林施用氮磷钾的最佳施肥量及其最佳配比。４．５ａ的试验结果表明：最佳施肥量为４５０ｋｇ／ｈｍ￣２，氮磷钾配比为氮∶磷∶钾＝４∶３∶０，二者组成最佳组合的立木蓄积量为４１．７８１ｍ￣３／ｈｍ￣２，是对照的１９０．３％。它比其它各种处理的立木蓄积量都高，差异显著，施肥使毛白杨叶中的叶绿素和氮磷钾的含量提高，也提高了叶重和叶面积等指标。因而加速了毛白杨的生长量。但施肥量过大反而抑制了毛白杨生长。氮∶磷的比值以１．３３为宜。该土含钾多不施钾肥。毛白杨的年生长过程，高和径各有两次速生期。毛白杨施肥的产值净增额是投入的２．７９倍。

Fertilization Amounts Applied to the Artificial YoungForest of Populus tomentosa Carr. on Sandy Soil and Their Ratios

The study deals with the optimum amount offertilization of N,Pand K ap-plied to the fast growing and high yield artificial forest of Populus tomentosa and their ratios.The result of experiment for 4.5 years indicates that the optimum amount of fertilization is450 kg/hm￣2,the optimum ratio of N, P and K is N∶P∶K=4∶3∶0 ,and the amount ofgrowes stock of the above combination is 41.798m￣3/hm￣2,90.3%higher than that of the con-trol and higher than that of other treatments. Fertilization increases the contents of chloro-phyl and N, P and K in the leaves of Populus tomentosa,and also raises the indices of leafweight and leaf area, thus accelerates the growth of POpulus tomentosa,However,excessiveamount of fertilization will impede its growth.Fertilizer K should not be applied becausemuch K is contained in the soil of the experimental site. N∶P=1.33;the production valueof applied fertilizer of Populus tomentosa Carr.is 279% of investment.