Density of neyv cotton lines under intercropping system with soybeanThe ield trial on different crop densities for new cotton lines under intercropping system with soybean was conducted in Mojosari. East Java from May lo October 2000 on the rice ield ater harvest. The purpose of the study was to investigate die optimum population for new cotton lines under intercropping with soybean The field experiment was arranged in a Split Plot Design with three replications. Pour new cotton lines were allocated lo main plots 92016 6, 91001/29.2 (okra leal). 88003/16/2 and Kanesia 7 'Three crop arrangements were allocated to sub-plots: 1 (1 ):3 [1 cotton row (I plant/hole) in between 3 rows of soybean), 2(1 ):4 [ 2 coton rows (1 plant/hole) in between 4 rows of soybean, and 1(2):3 (1 cotton row (2 planlholc) in between 3 rows of soybean). Two replications for sole crops of cotton and soybean were included in this expeiment lo compare both cropping systems. Research showed that by keeping one cotton plant/hole under intercropping system wi(h soybean in arrangement of 1:3 11 conon row in between 3 rows of soybean), increased the photosynthetic efficiency from 5 9 x 10"* to 9.4 x 10"* mg C02/mg H20, causing cotton yield increased from 1167.2 to 1 251.6 kg/ha; however soybean yield did not differ between different propotions of cotton and soybean (846 kg/ha) Under arrangement of Iwo cotton rows * four rows of soybean, the photosynthetic efficiency increased from 5.9 x 10"1 to 7.7 x 10"* mg COj'mg HjO resulted in increased cotton yield from I 167.2 lo 1 206.2 kgha Ihe yield of line 88003/16 2 (1 323.3 kgha) did not differ with that on Kanesia 7 (I 365.2 kg/ha); both were higher than those on 92016/6 (1 096.9 kg/ha) and 91001 /29/2 (1 048.0 kgha).