Effect of N-levels on Growth and Dry Matter Accumlation of Sorghum-Sudangrass Hybrid ( Sorghum bicolor $\times$ S. sudanense ) , Pioneer 988

질소시비수준이 Pioneer 988 ( Sorghum bicolor $\times$ S.Sudanesse ) 의 엽생육 및 건물생산에 미치는 영향

The purpose of this experiment was to find out fundamental data for the cultivation of sorghum-sudangrass hybrid. Leaf area index and dry matter accumulation were investigated with 3-levels of nitrogen application,15, 25, 35kg per 10a during the period of initial growth from the 8th leaf emergence to the late blooming stage. The results obtained were as follows: Leaf emergence increased as growth progressed and in the same pattern at all N-levels. After the heading stage, the value was 15 at all N-levels. Leaf area index (LAI) increased as growth progressed and rapidly till the booting stage. At 15kg N-level the values were larger till the ear formation stage, and at 35tg N-level the values were larger than other N-levels after the booting stage. At the late blooming stage LAI reached 8.13 at 35kg N-level. The value of dry matter accumulation was the highest at 35kg N-level at the late blooming stage, and as was the same in the value of crop growth rate (CGR). There was a tendency that before the booting stage the enlargement of leaf area contributed to dry matter accumulation and after the booting stage did the increase of net assimilation rate (NAR) .

種實用 수수와 수단그라스의 交雜種인 Pioneer 988의, 窒素施肥水準에 따른 時期別 生育 및 乾物生産量을 조사하기 위하여 本 硏究를 실시하였다. 窒素肥科는 成分量으로 10a當 15, 25, 35kg을 施用하였으며 幼植物로부터 開花後期까지의 生育期間게 몇가지 特性을 調麥한바 그 結果는 다음과 같이 要約된다. 1. 出現葉數는 生育이 進行됨에 따라 증가했는데 穗孕期까지 급격한 증가를 보였고, 出穗期에는 最終葉인 15葉이 出現했다. 2. 葉面積指數는 生育의 進行에 따라 증가했는데, 특히 穗孕期까지 그 增加가 급격했으며, 室素施肥水準別로는 幼穗分化期까지 15kg 施肥區에서 컷으나 穗孕期 以後에는 35kg 施肥區에서 컷다. 3. 乾物收量은 穗孕期 以前에는 15kg 施肥區에서 많았으나, 穗孕期 以後에는 35kg 施肥區에서 많았다. 4 乾物生産速度는 純同化率 및 平均 葉面積指數와 밀접한 관계가 있었으며 生育後期에는 純同化率의 增加와 더욱 밀접한 관계를 나타냈다.