施肥条件ならびに刈り取り時期の差が兼用型ソルガムの生産量と飼料価値に及ぼす影響

The effects of additional fertilizer and harvesting time on the production and nutritive value in dual purpose sorghum were examined. Experimental fields received the dressing of slaked lime(200kg/loa) and compound fertilizer(60kg/10a) at seeding. The additionally fertilized group was received further twice dressings of urea(15kg/10a each), but the other group recieved no further applications. Each crop was harvested at the boot stage or the milk-ripe stage. The results were summarized as follows :
1. Total dry matter yield of the first and second cutting crops in each treatment ranged from 950kg(unfertilized, boot stage cutting) to 1,870kg/10a(fertilized, milk-ripe stage cutting) and the yield of additionally fertilized crop was 173-211% of unfertilized crop in first cutting.
2. The crude protein content in unfertilized crop was very low but the contents of other chemical components in unfertilized crop dld not differ from those in fertilized one. The crop harvested at milk-ripe stage showed lower crude fiber and higher nitrogen -free-extract contents than those of the crop harvested at boot stage.
3. The neutral detergent fiber(NDF) digestibility measured by in vitro technique was lower in fertilized crop than in unfertilized crop, and these value highly correlated with the hemlcellulose content or lignin contentin the NDF of crops.