초록
산지(山地)의 경사도(傾斜度)($10^{\circ}$, $20^{\circ}$, $30^{\circ}$) 및 3요소(要素) $N-P_2O_5-K_2O$ (0-0-0, 14-10-10, 28-25-25, 42-40-40kg/10a) 수준(水準)이 겉뿌림 산지초지(山地草地)(orchardgrass, tall fescue, redtop, ladino clover 혼파(混播))의 조성(造成), 생산성, 식생(植生) 및 목초품질등(牧草品質等)에 미치는 영향(影響)을 구명(究明)하였다. 본교(本橋)에서는 토양(土壤) 및 목초중(牧草中) 무기양분(無機養分)의 함량(含量) 및 상호비율(相互比率)을 grass tetany 발생위험성(發生危驗性)과 연관(聯關)하여 검토(檢討)하였다. 1. 토양중(土壤中) 치환성(置換性) Mg 함량(含量)이 낮고, CEC, K, Ca에 대한 Mg 비율(比率)이 부적합(不適合)하여 목초(牧草)의 정상생육(正常生育)에 불리(不利)하였고, tetany 발생(發生) 가능도(可能度)를 높여주는 조건(條件)이였다. 이는 경사도(傾斜度) 및 3요소시용수준(要素施用水準)이 증가(增加)된 토양(土壤)일수록 더욱 불량(不良)한 조건(條件)이 되었다. 2. tetany발생(發生)이 가능(可能)한 조건(條件)(목초중(牧草中) Mg 함량(含量) < 0.2%, K > 2.5%, K/(Ca＋Mg)당량비(當量比) > 2.2)과 비교(比較)할때 Mg함량(含量)은 0.09~0.14%, 3요소(要素) 보비수준시(普肥水準時) K 함량(含量) 2.6% 및 K/Ca+Mg 당량비(當量比) 2.5를 보였다. 일반적(一般的)으로 경사도(傾斜度) 및 3요소(要素) 시용수준(施用水準)이 증가(增加)할수록 tetany 발생(發生) 위험성(危驗性)이 높아지는 불리(不利)한 지성(持性)을 나타내었다. 3. 산지초지(山地草地)의 토양(土壤) 및 목초중(牧草中) Mg 함량(含量) 및 염기간(鹽基間)의 상대비(相對比)가 목초생육(牧草生育) 뿐만 아니라 가축건강유지(家畜健康維持)에 부족(不足)한 수준(水準)이었으며 경사도(傾斜度) 및 3요소(要素) 시용수준(施用水準)이 증가(增加)할수록 Mg 시비(施肥)와 방목우(放牧牛)에 별도(別途)의 Mg 염(鹽)의 공급(供給)이 필요(必要)하였다. 4. 목초중(牧草中) Ca/P비율(比率)은 경사도별(傾斜度別) 차이(差異)는 없으나 3요소(要素) 시용수준(施用水準)이 증가(增加)할수록 낮아지며 그 범위(範圍)는 평균(平均) 1.0~2.0을 나타내었다.
This field experiment was undertaken to assess the effects of three levels of inclination ($10^{\circ}$, $20^{\circ}$ and $30^{\circ}$) and four rates of $N-P_2O_5-K_2O$ (0-0-0, 14-10-10, 28-25-25, and 42-40-40 kg/10a) on the hilly pasture concerning to establishment, forage yield and quality, and botanical composition in the mixed grass-clover sward set up on a new reclaimed woodland by an oversowing method. This part was concerned with the concentration and mutual balance of mineral nutrients in relation to grass tetany hazard. The results obtained were summarized as follows: 1. Concentration of exchangeable Mg, relative proportions of Mg to CEC, K, and Ca in soil were considerably below the critical level for good forage growth and prevention of grass tetany. These properties were rather worsened by increasing the inclination grade and the NPK rate. 2. Compared with the critical level for the likelihood of tetany (Mg < 0.2%, K > 2.5%, and K/(Ca+Mg) equivalent ratio > 2.2 in forages in DM basis), mean concentration of Mg in mixed forages turned out to range from 0.09 to 0.14%. 2.6% of K concentration and 2.5 of K/(Ca+Mg) equivalent ratio were shown to be at a normal NPK rate. The likelihood of grass tetany was generally enhanced by increasing the inclination grade and the NPK rate. 3. The increasing of the inclination grade and NPK rate rather aggravated the low Mg concentration and unbalanced mutual ratios of mineral nutrients, from which resulted the grass tetany hazard and the depression of forage growth. To prevent these two resulted factors, Mg fertilization on grassland and/or extra Mg supplement to dairy cattle needed to be carried out. 4. The Ca/P ratios in the mixed forages ranging from 1.0 to 2.0 were reduced by the increased rate of NPK, whereas the difference due to inclination grade was yet to be recognized.
(Suncheon National University)
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