پژوهشهای زراعی ایران (Dec 2020)
Effect of Different Intercropping Ratios of Three Bean Ecotypes as Replacement Series on their Physiological Indices
Abstract
Introduction Recently self-sustaining, diversified, low-input, and energy-efficient agricultural systems like intercropping have been considered as the efficient way to achieve the sustainability in agriculture. Intercropping as an old agricultural practice, have been followed especially at the small scale and subsistence farming. It can be defined as the agricultural practice of growing two or more crops or ecotypes together in the same field. Intercropping brings diversity of species in the cropping systems, and is considered to make the systems more resilient against environmental perturbations, thus enhancing food security. It provides high insurance against crop failure, especially in the extreme weather conditions like temperature stress, drought, flood, frost, pest infestation etc. In fact, intercropping is claimed to be one of the most significant cropping techniques in sustainable agriculture, and many researches and reviews attribute its utilization to the number of environmental benefits from promoting land biodiversity to diversifying agricultural outcome. Legumes after cereals are the second source of human food and in Iran they are the second most important food. Due to the importance of legume intercropping in the sustainability of agricultural systems, the objective of the present work was to evaluate the effect of row intercropping of three bean ecotypes red bean, pinto bean and cowpea bean as replacement series on the physiological growth indices under climatic conditions of Mashhad. Materials and Methods This experiment was conducted based on a randomized complete block design with nine treatments and three replications at the Agricultural Research Station, Faculty of Agriculture Ferdowsi University of Mashhad during 2016-2017 growing season. Treatments were 75% red bean+ 25% pinto bean, 75% red bean+ 25% cowpea bean, 25% red bean+ 75% pinto bean, 25% red bean+ 75% cowpea bean, 75% pinto bean+ 25% cowpea bean, 75% cowpea bean+ 25% pinto bean and their monoculture. In order to measure the growth indices, the destructive samplings were carried out every 14 days from 0.15 m2 of row in each plot. All bean ecotypes were harvested by cutting at the soil surface. The studied indices were leaf area index (LAI), dry matter accumulation (DM), crop growth rate (CGR), relative growth rate (RGR) and net assimilation rate (NAR). Results and Discussion The highest leaf area index for red bean, pinto bean and cowpea ecotypes were observed in their monoculture with 2.45, 1.45 and 3.60, respectively. The fast period of vegetative growth and dry matter accumulation were observed at 65-80 days after planting with a small decline afterwards until physiological maturity. The maximum dry matter accumulation for these ecotypes was obtained in their monoculture. Crop growth rate reached its peak 65 days after emergence followed by a decreasing trend afterwards. The highest crop growth rate was observed in pinto bean with 27 g m-2 day-1. At the beginning of growth stage, due to more penetration of light into the canopy and less shadow of the leaves the less respiration, RGR was more and its reduction slope was less. As time passes and vegetative and reproductive organs grow more, the shadow of leaves on each other increases and therefore after words RGR decreased. Also, net assimilation rate reached to its peak 60 days after emerging and decreased. Conclusions The results of showed that intercropping of bean ecotypes with increasing plant density, increased the leaf area index (LAI) and dry matter accumulation (DM) of both crops in monoculture and mixed culture which could be due to increased vegetation and it's closer to optimum density in mixed culture and better use of environmental resources. However due to different criteria of these ecotypes associated with better use of water, radiation and nutrient resources when they are intercropped, physiological growth indices were increased. Overall following this agroecological practice in cropping systems could keep contribution to move the current agroecosystems one step towards sustainability. Acknowledgements This research was funded by Vice Chancellor for Research of Ferdowsi University of Mashhad, which is hereby acknowledged.
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