The strip intercropping system has used due to many advantages. Many researches supported these crop systems are usually equal to or better than monoculture crop systems in both total production and profit. There was no research to examine the important ecological factors in the competition between crops. A strip intercropping system composed of adjacent narrow strips of corn, soybean, and oat/legumes has been investigated in Iowa, USA. This study conducted to investigate why and how the differences in soybean yield are produced and affected by light, one of the microclimate, of the strip intercropping system. In height, the two rows of soybean closest to corn were taller than the two rows near the then-empty oat strip. The height of each crop decreased as the amount of light received increased. Weight of plant parts was lowest in row 1, nearest corn, and highest in row 4, next to the vacant oat strip. Daily photon flux density(PFD) increased with increasing distance from corn, with the highest value occurring on the edge next to the empty oat strip. Analyses of the relationship between light and biomass of soybean showed that all biomass measurements had a positive relationship to total PFD per day except height.

• Kyujung Van