Yield-density effects on growth and biomass partitioning in Leucaena leucocephala seedlings

Experiments were conducted to study the effects of density on growth and biomass partitioning of Leucaena leucocephala seedlings.Four plantations with densities of 10,000,20,000,40,000,and 80,000 seedlings ha^-1 were evaluated only from 15 to 25 months after planting.At 15 months,crown height and width decreased with increasing density.Seedling height/dbh ratios increased with increasing density.Biomass increased with greater density according to the yield–density effect equation,which was evident for all densities.With increasing age,biomass division to branches and leaves increased,whereas partitioning to roots decreased in the 10,000 and 20,000 seedlings ha-1 plantings.Partitioning to branches and leaves remained relatively steady,while partitioning to roots increased in the 40,000 and 80,000 seedlings ha^-1 plantings.Biomass division into stem and bark components remained relatively steady in all densities.Yield–density and organ yield–density curves shifted upward with increasing seedling age on a log–log graph throughout the experimental period.

Herbaceous Cultivation Test of Mulberry in Sichuan Sericultural Area

With Guiteyou 2 as the test mulberry variety, mulberry herbaceous cultivation field was established at the planting densities of 60 000,90 000 and 120 000 plants/hm2, respectively. Hybrid mulberry herbaceous cultivation test was conducted, with Tongxiangqing mulberry field of mid-fist-form at conventional planting density of 4 995 plants/hm2 as the control. The results showed that the leaf yield of herbaceous cultivation mulberry was closely related to the planting density. With the increasing planting density, the leaf yield per plant was decreasing, but the leaf yield per unit area of mulberry field was increasing. The annual leaf yield per unit area in the mulberry field with the average planting density of 120 000 plants/hm2 was 37 560 kg/hm2, 2.14 times of that of the control field. The moisture content of mulberry leaf in herbaceous cultivation field was 4.74% higher than the control; the contents of crude protein, crude fat, crude fiber and crude ash were 1.264%, 0.014%, 0.744% and 0.002%lower than the control, respectively. Comparison of leaf rearing with herbaceous cultivation mulberry and control mulberry showed that there was no significant difference in growth status of silkworm. The cocoon weight, cocoon shell weight, cocoon yield per 10 000 larvae, cocoon filament length and non-broken filament length of Chuanshan × Shushui were 12.81%, 14.29%, 13.85%, 5.95% and 7.68% lower than the control, respectively; but the percentage of common cocoons was 0.16% higher than the control; the cleanness and neatness were 0.2 and 1.25 points higher than the control;the filament size was 0.196 dtex lower than the control. The cocoon weight, cocoon shell weight, cocoon yield per 10 000 larvae, cocoon filament length and non-broken filament length of Jingsong × Haoyue were 11.06%, 10.20%, 11.53%, 9.46% and 9.03% lower than the control, respectively;but the percentage of common cocoons was 1.77% higher than the control; the cleanness and neatness were 0.12 and 2.50 points higher the control;and the filament size was 0.196 dtex lower than the control.