Document Type : Research Article
Department of Agronomy, Sari University of Agricultural Sciences and Natural Resources, Sari, Iran.
Department of Genetic & Agricultural Biotechnologhy Institute of Tabarestan, Sari University of Agricultural Sciences and Natural Resources, Sari, Iran
Most research on intercropping cultivation in the past has focused on seed yield and yield components, and less attention has been paid to below-ground interaction processes. However, the connection of plants in the below-ground sector is a vital issue in identifying the mechanism of competition and productivity in intercropping cultivation. Meanwhile, the selection of a legume plant due to the biological nitrogen fixation (BNF) increases the productivity in intercropping cultivation. However, the BNF by the legume component can be affected by the component crop in intercropping cultivation. Therefore, creating the optimum conditions for the BNF in planting ratios plays an essential role in the dynamics of inter-species interaction. Therefore, this study aimed to evaluate the interactions of the below-ground sector and the percentage of nitrogen derived from the atmosphere in different ratios of intercropping cultivation.
Material and Methods
A field experiment was conducted for two years (2018-19) at the research farm of Sari agricultural science and natural resources university, Iran (33º, 36ʹ N, 53º, 03ʹ E with 43 m altitude). The experimental design was a randomized complete block with four replications. The experimental treatment was 75% soybean + 25% niger, 50% soybean + 50% niger, 25% Soybean+75% niger based on the replacement method and monoculture. For example, a 25:75 combination consisted of three rows of planting a soybean and one row of niger and vice versa in the 75:25 combinations. The 50:50 also included planting two rows of each of the studied plants. This study investigated the percentage of nitrogen derived from the atmosphere, nitrogen yield, total enzymatic activity of the soil, and root activity in different planting ratios.
Result and Discussion
The percentage of nitrogen derived from the atmosphere (Ndfa) in all different planting ratios was higher than a single soybean crop. This trend continued until it reached 90 days after planting. At 75 and 90 days after planting, the highest Ndfa has related to 50:50 and 75:25 planting ratios in both cultivation years. Also, the yield of Ndfa was higher than expected in planting ratios, and its value increased further as it approached the final stages of growth. In addition to the above, the total microbial activity of soil in different ratios of intercropping cultivation was higher than the monoculture of the studied plants. Its amount in 50:50 planting ratio was 16.38 and 31.69% higher than monoculture soybean (0: 100) and niger (0: 100) at 60 days after planting, respectively. The most increased total microbial activity of the ground in niger and soybean plants in the middle and late stages of growth was observed at a depth of 0-20 and 10-30 cm, respectively. Also, niger plant in different ratios of intercropping cultivation, while increasing root activity, have a higher number of secondary compounds in root extract. In general, the increase in root activity in the late stages of growth was accompanied by a decrease in the number of rows of niger plants, especially in the planting ratio of 75:25. Also, the total phenol and flavonoids in the niger root extract increased to 105 days after planting and then decreased. Thus, in general, different ratios of intercropping cultivation were more successful in producing secondary compounds than the monoculture of niger.
Increasing the significance of nitrogen derived from the atmosphere and the other activity of niger root as a complementary plant in intercropping cultivation ratios can play an essential role in the dynamics of underground sector interactions intercropping cultivation patterns. In addition to the above results and based on the total microbial activity of the soil, the complementary structure of niger and soybean root in intercropping cultivation can affect the ability of interspecific competition in intercropping cultivation by distinguishing ecological niche even in a short period.