Evaluation of Radiation Absorption and Use Efficiency in intercropped Sweet corn (Zea mays Var. saccharata) with Potato (Solanum tuberosum)

Intercropping is one of the suitable management methods in crops production that improves absorption and use efficiency of resources by plants. Higher production in intercropping systems compared to sole cropping systems is attributed to morphological differences and different needs of the plants to utilize of environmental resources such as light, water and nutrients. There are the adequate logical and reasonable grounds to intercropping of potato and sweet corn because of their economic importance and physiological and morphological differences. Furthermore, harvesting of these crops had not any disorder. While, access to information such as resources use efficiency is need to find the best intercropping combination. Then the objective of this study was evaluation of radiation absorption and use efficiency (RUE) of sweet corn (Zea mays. Var. saccharata) intercropped with potato (Solanum tuberosum) under Kermanshah climate condition. The experiment was conducted based on a randomized complete block design with three replications in the research farm of campus of agriculture and natural resources, Razi University, Kermanshah, Iran during the growing season of 2013. Treatments were included the intercropping of sweet corn (Chase) and potato (Agria) with 1:1, 2:2, 2:1, 1:2 ratios (that shows the sweet corn and potato rows, respectively) along with sole cropping of sweet corn and potatoes. Planting intra rows spacing were 13 and 25 cm for sweet corn and potato respectively. Planting inter rows were 75 cm with 7 m long for both crops. The destruction sampling was done at two weeks after emergence. In every stage, three plants were selected from each plot randomly. Absorbed radiation was calculated by simulated entrance radiation and absorbed radiation percent multiply: and cumulative total absorbed radiation was obtained by simulated entrance radiation× integral of absorbed daily radiation to time ratio. Ultimately, RUE of sweet corn and potato was evaluated as g MJ-1 by linear regression slope between total accumulative dry mater (g m-2) and accumulative daily radiation (MJ m-2) for each plot individually. Results showed that leaf area index (LAI) was higher in all intercropping treatments than sole cropping. Among intercropping patterns, the highest and lowest LAI were observed in 2 rows sweet corn + 1 row potato (4.12) and 1 row sweet corn + 2 rows potato (3.4), respectively. Also dry mater accumulation trend was affected by intercropping patterns and radiation absorption increased by sweet corn and potato canopy appropriate to LAI rising. RUE of sweet corn and potato in intercropping was higher than of sole cropping. Among different intercropping patterns, the highest amount of sweet corn RUE were 2.18 and 1.86 g MJ-1 ,respectively that obtained in intercropping of 1 row sweet corn +2 rows potato. The highest sweet corn shelled kernel for conserving (3300 kg ha-1) and potato yield (9460 k ha-1) were obtained in 2 row sweet corn + 1 rows potato and 2 row sweet corn + 2 rows potato, respectively. On the contrary, increasing the number of potato rows resulted in higher RUE. Results also showed that land equivalent ratios were bigger than 1 in all intercropping patterns. Pattern of 2 rows sweet corn + 1 row potato, was recommended with the highest LER (1.41) economically. The additional obtained yield can attribute to better radiation use because of the morphological and physiological differences between sweet corn and potato. There was no considerable dissimilarity in dry matter accumulation trend between intercropping of sweet corn with potato and their sole cropping because of little plants in early growth season. However, the dry mater trend continued as linear stage at 30 days after sowing date as the differences were appeared between intercropping and sole cropping plots. Compared to sole cropping, results of present study showed that the intercropping of sweet corn and potato resulted in LAI improvement, dry matter rising, more efficiency in radiation absorption and increasing of radiation use efficiency. Also this intercropping is recommended economically based on obtained LERs. Therefore, this study suggests the intercropping of 2 rows sweet corn + 2 rows potato economically. However, the water consumption and water use efficiency must be investigated to choose the best intercropping pattern.