Improvement of resource use efficiency, profitability and productivity of potato by intercropping with green bean

Background and objectives: Potato (Solanum tuberosum L.) is a global food crop, and Iran with more than 5 million tons of production, ranks 13th among the world’s biggest producers of potatoes. Hamedan province is also one of the main potato producers in Iran. In this crop, the yields of quantity and quality are very dependent on an adequate application of nitrogen. However, the relatively shallow root system of the potato crop, coupled with its large nitrogen and water requirement increases the risk of nitrogen leaching. Therefore, optimizing N consumption for potato is important, both for maximizing production and for minimizing N loss to groundwater. Sustainable agriculture can play a significant role in achieving this goal. One of the methods for achieving sustainable agriculture is to create diversity by using intercropping of different plants in agriculture. Hence, the purpose of this experiment was to evaluate the response of potato as well as the resources use efficiency to intercropping with green bean.
Materials and Methods: The experiment was conducted as a factorial based on randomized complete block design with three replications in 2016 growing season at the Research Farm of the Bu-Ali Sina University. Planting patterns in four levels (potato sole cropping, planting green bean between potato rows, planting green bean within potato rows, and planting green bean between and within potato rows), and three levels of urea fertilizer (0, 174 and 348 kg urea/ha) were the experimental factors. To calculate the advantages of intercropping, the pure stand of green bean was also cultivated in three replications. In intercropping, 50% of the density of green bean was added to pure stand of potato. Tuber yield, percentage and yield of tubers in different size, leaf chlorophyll content of potato, nitrogen and water use efficiency, as well as total relative yield (RYT) and land equivalent coefficient (LEC) indices were calculated and evaluated. SAS 9.1 software were used for analysis of variance (ANOVA) calculations. The difference between the means was evaluated by the least significant difference (LSD) method at the level of 5% probability.
Results: The interaction of treatments on traits was significant except for the number of main stems and tubers per plant. The highest number and weight of root nodules were obtained from the green bean planting between potato rows with consumption of 174 kg urea/ha, and the lowest values of these were belonged to the green bean planting within potato rows with consumption of 348 kg urea/ha. Also the highest potato leaf chlorophyll was revealed at the green bean planting between potato rows with consumption of 174 kg urea/ha. Maximum total tuber yield and yield of commercial tubers were revealed at the green bean planting between potato rows with consumption of 348 kg urea/ha. However, this treatment did not show a significant difference with the treatment of green bean planting between potato rows at the fertilizer level of 174 kg urea/ha for the traits of total tuber yield and yield of commercial tubers. The highest water and urea fertilizer use efficiency were obtained from the treatment of green bean planting between potato rows at the fertilizer level of 174 kg urea/ha. Maximum RVT and LEC were achieved at green bean planting between potato rows with consumption of 174 kg urea/ha.
Conclusion: Generally, green bean planting between potato rows with consumption of 174 kg urea/ha compare to potato sole cropping with application of 348 kg urea/ha, improved the yield of potato and the efficiency of resources use. Therefore, it seems that this planting pattern is low input agricultural techniques and in addition to the satisfactory production can also reduce nitrogen chemical fertilizer consumption.