A field experiment was conducted to study both the distribution characteristics of photosynthetically active radiation (PAR) in the soybean canopy and their relationships with dry matter production. The soybean cultivars 'Hwanggeumkong' and 'Paldalkong' were sown with the spaces of 60~times 15cm and 30~times 15cm at Suwon on May 20 and on June 20 in 1989. The ratio of PAR to the total shortwave radiation was estimated by the empirical equation derived from sunshine hours and direct incoming radiation. The functional relationships between the PAR interception and the leaf area index were expressed as a function of Beer's law. The extinction coefficients(k) in the functions ranged from 0.77 to 0.92. The values of k were greater at higher planting density, but they were affected neither by planting dates nor by varieties. The reflection ratio of PAR(α ) was determined by the exponential function as below; α =α p-(α p-α o) exp(-kㆍLAI) where α p was the reflectance at the maximum LAI and α o was that of the bare soil. The ap ranged from 0.025 to 0.035 and α o ranged from 0.11 to 0.12, respectively. The reflected PAR ranged from 0.049 to 0.064 and the transmitted PAR ranged from 0.168 to 0.340 until maximum dry weights were observed. The slope from the linear regression of dry matter on absorbed PAR, conversion efficiency, ranged from 1.30 to 2.3g MJ-1 during the growing season until maximum dry weight was reached. The total dry matter yield above ground (TDM) increased with the increases in the conversion efficiency. TDM was higher in Hwanggeumkong than Paldalkong and higher in the space of 30~times 15cm than 60~times 15cm, Paldalkong showed higher harvest index than Hwanggeumkong. than Hwanggeumkong.

콩군락에 흡수된 단파폭사와 건물생산과의 관계를 단경밀식적응품종인 팔달콩을 공시하여 조사한 결과를 요약하면 다음과 같다. 1. 단파폭사의 군락에서의 감쇄계수는 0.53, 총투과된 양은 입사된 단파폭사량의 31.9%이었다. 2. 생육시기별 지하부 건물중과 그 기간에 군락이 흡수한 단파폭사의 적산치는 등숙기인 출현후 88일항까지는 직선적 비례관계가 성립하였고, 건물로의 변환효율인 비례계수는 1.45gMJ1이었다. 3. 생육기간의 전체반사율은 24.7%이었으며 엽면적지수(LAI) 2.5 이상에서는 입사량에서 투과량을 뺀값과 반사폭사량간의 상관도가 높았다.