عنوان مقاله [English]
Agriculture plays an essential role in providing food to society, and in order to achieve sustainability in the agricultural sector, resources must be used in the best possible way. In order to achieve the maximum possible yield, it is necessary for the crop plant to use the environmental factors, water, nutrients, light and carbon dioxide, with the maximum possible efficiency. The maximum use of the factors needed for growth is achieved only when the plant community exerts maximum pressure on these factors. In general, intercropping is one of the ways to achieve sustainable agriculture, with higher yields without increasing agricultural inputs and increasing the absorption and productivity of environmental factors. Researchers in the intercropping of corn and mung bean reported that the mixed cultivation systems used environmental resources more effectively compared to the sole cropping of corn and mung bean. For this reason, nowadays, many plants, especially legumes, are cultivated in a intercropping form due to the ability to fix nitrogen. Due to the lack of resources regarding the effect of planting direction on plant yield, this study was conducted in order to reduce water evaporation through soil temperature control, by changing the planting direction and replacement intercropping system of sunflower with cowpea.
Materials and Methods
This research was carried out in March 2016 in the research farm of Zabul University Agricultural Research Institute. The experiment was split plot based on randomized complete block design with three replications at Research Farm of Agricultural Research Institute of Zabol University. Treatment experiments included two levels of planting direction (North-South and East-West) as the main plot and intercropping system was as a sub-plot in five levels were considered: (100 percent pure sunflower), (100 percent pure beans), (50percent sunflower plus 50percent beans) (25percent beans plus 75percent sunflower) and (75percent beans plus 25percent sunflower). In order to evaluate the usefulness of intercropping, was calculated the index of land equivalent ratio. Data analysis was done using the statistical software SAS version 9.1 and the comparison of the means was done using the least significant difference (LSD) test at the 5% level.
Results and Discussion
The results obtained from the analysis of variance showed that the active photosynthetic radiation was significantly affected by the planting direction at the level of 1%.The maximum absorption of PAR was in the east-west cultivation direction compared to the north-south treatment (77.90%), which was 24.6% more than the north-south direction. The results obtained from the analysis of variance table showed that the cultivation direction and intercropping systems had a very significant effect on the amount of phosphorus in the soil after harvest at the probability level of one percent.The comparison of means treatments showed an increase in the amount of phosphorus in the soil in the direction of east-west cultivation by 15% compared to the direction of north-south cultivation. The highest amount of soil potassium was obtained in the east-west treatment and the intercropping system of 50% sunflower plus 50% beans (24.7 ppm). The lowest amount of soil potassium (16.15 ppm) was obtained in the treatment of east-west cultivation and the intercropping system of 75% sunflower plus 25% beans. The relative advantage of intercropping is expressed by the land equivalent ratio. The increase in the ratio of equal land per unit shows the relative usefulness of intercropping compared to sole cropping of each of the mixed components. The comparison of means of the intercropping system showed that among the treatments, the mixture of 75% sunflower plus 25% beans had the highest land equivalent ratio (2.54).
It seems that in order to maintain humidity and make maximum use of limited water resources and obtain high yield, intercropping system of 75% sunflower plus 25% cowpea and planting direction the prevailing wind of the region (east-west) should be suitable for this region and regions with similar climate and windy conditions.
we would like to thank the chairman and the respected staff of the Agricultural Research Institute of Zabul University who sincerely accompanied us in the implementation of this thesis.
Key words: Land equivalent ratio, Orientation planting, PAR, Soil temperature, Soil moisture