Studies on the Grassland Development in the Forest Ⅷ. Effect of shading degrees on the quality, digestibility and nitrate nitrogen concentration of main grasses

林間草地 開發에 關한 硏究 Ⅷ. 遮光程度가 主要 牧草의 品質, 消化率 및 窒酸態窒素含量에 미치는 影響

A field experiment was conduted to determine the effects of shading degrees (O: full sunlight, 25, 50 and 75%) on the proximate components, cell wall constituents (CWC), digestibility, water soluble carbohydrates (WSC) and nitrate nitrogen ($NO_3$-N) concentration of grasses grown in forest. For the test different artificial shading houses were established and pasutre species used were orchardgrass, timothy, perennial ryegrass and ladino clover. the experiment was performed at LES in Suwon, 1985 1. Considering proximate components, CWC and digestibility of grasses, ladino clover showed the best quality, and then perennial ryegrass. 2. The contents of crude protein, crude ash, and digestibility of grasses were increased with shadking, regardless of pasture species. As the shading degrees are increased, the contents of crude fibe in orchardgrass, perennial ryegrass and timothy were decreased, while that in ladino clover was increased with shading. 3. Grasses grwon in spring showed higher digestibility than those grwon in summer season. 4. The content of WSC was the highest in perennial ryegrass, and then ladino clover, orchardgrass, and timothy, in that order. Also WSC was decreased as the shading degrees are in creased. 5. The content of $NO_3$-N was the highest in perennial ryegrass, and then orchardgrass, ladino clover and timothy, in that order. Also the $NO_3$-N was significantly increased with higher shading level. In the regression equation between shading degrees and $NO_3$-N ($r^2=0.90^{**},\;r^2=0.95^{**}$), shading degree of 43 to 44% was critical level, causing nitrate poisoning to animal. 6. Considering grass quality, dry matter yield and $NO_3$-N, less than 40% of shading degree (over 60% of full sunlight) was desirable for better grassland improvement, management and utilization in the forest.

本 실험은 林間草地의 改良과 管理 및 利用에 관한 基鍵資料를 얻고자 趣光程度를 0%區(無週光區), 25%, 50%, 75%로 인위적으로 조절하고. orchard grass, timothy, perennial ryegrass, ladino clover를 供試하여, 일반成分, 세포벽構成物質(CWC),,消化率, 可溶性탄수化物 (WSC) 함량 및 실산유실요 (NO, - N) 含量등을 分析하였으며 1985년도 축산시험장 草地시험포에서 수행되었다. 1. 一般成分과 CWC含量 및 消化率을 고려해 볼 때 ladino clover가 화본과목장에 비해 품질이 좋았으며, 未本科목장중에서는 perennial ryegrass의 品質이 좋았다. 2.粗蛋白質, 조회분 및 消化率은 草種에 관계없이 차광을 많이 할수록 增加하였으며, 粗織維系 統은 차광을 많이 할수록 未本科救草에서는 減少하였으나 ladino clover에서는 오히려 曾加하였다. 3.利用時期에 따른 목초의 消化率은 봄철에 자란 목초는 여름철 고온조건하에서 자란 옥초에 비해 良好하였다. 4.草種別 WSC 含量은 perennial ryegrass>ladino clover$\geq$orchardgrass$\geq$timothy 順이었으며 차광을 많이 할수록 WSC含量은 減少하여 (P< 0.05) 無遮光區$\geq$25%週光區$\leq$50%차광구$\geq$75%차광구 순 이었다. 5.草種別 NO,-N 含量은 perennial ryegrass orchardgrass ladino clover timothy 順이었으며, 차광을 많이 할수록 $NO_3$-N含量은 급격히 增加하 여 (P< 0.05) 75%차광구>50%차광구 25%차광구 無차광구 순이었다. 차광정도와 $NO_3$-N 함량과의 회귀식에서($r^2$=0.90**,$r^2$=0.95**) 43~44% 이상의 차광은 실산중독 위험수준 이상이었다. 6. 以上의 결과로서 임간초지개랑시에는 가축에게 실효중독을 야기시키지 않고 목초의 품질과 수량등을 고려한 한계 차광정도는 40%정도(자연광량의 60% 以上 受光條件)로 생각된다.