Study of radiation use efficiency and seed yield in millet and soybean intercropped under low nitrogen conditions

To evaluate the competition of millet (Panicum miliaceum L.) and soybean (Glycine max (L) Merrill) in the intercropping system, a field experiment in two years (2018-19) was conducted in a randomized complete block design with four replications at the Sari Agricultural Science and Natural Resources university. The planting ratios were 0:100, 25:75, 50:50, 75:25, and 100:0 (Soybean: Millet, respectively). The results showed that the radiation use efficiency (RUE) was higher in different intercropping ratios than the millet monoculture (0:100). In different intercropping ratios, the RUE of millet decreased significantly with increasing the share of soybean. So that in the 105 days after planting, the RUE of millet in 75:25 was 47.74 and 29.41 percent less than the expected values in studied years, respectively. Also, the planting ratio of 25:75 in the 90 days after planting had the highest chlorophyll a/b ratio in soybean and millet. The 25:75 had the most elevated land equivalent ratio index (1.23), and the millet actual yield loss (AYL) was only positive (2.01) in the 25:75. Therefore, increasing the RUE in intercropping culture and improving millet grain yield as the dominant species played an important role in increasing productivity in the planting ratio of 25:75.