The Evaluation of Resource Efficiency and Soil Fertility Indices in Pearl Millet (Panucum miliaceum L.) and Peanut ((Arachis hypogaea L.) Intercropping

Increase agricultural production to match the increasing demand for food sources is inevitable. It causes too much pressure on the agricultural resource base and threatens the sustainability of these systems. Intercropping is an important method of high production in agriculture. This technic can affect soil environmental condition. Sustainable Agriculture defines the proper management of agricultural resources which in addition to changing human needs, maintaining environmental quality and capacity of soil and water resources. The aim of this study was to investigate the competition between two types of millet and peanuts and determine the best planting ratio of mixed cropping.

In order to investigate the effect of density, weeding and different ratios of millet (Panucum miliaceum L. var Common) and peanuts (Arachis hypogaea L. var Goli), an experiment as factorial has been conducted in a randomized complete block design with three replications at the Agricultural Research Farm of Zabol University during 2012. The experimental treatment consisted of 4 planting ratio at (sole millet, 50% millet + 50% peanut, 100% millet + 100% peanut and sole peanut),  3 weeding levels (non-weeding, once weeding and twice weeding) and 2 levels of intervals between rows (40 and 50 centimeters). Traits evaluated by environmental resources including (Photosynthetically Active Radiation and temperature and humidity of soil), soil nutrient elements (Ca, Mg, Na, and C), and land equivalent ratio (LER) for evaluation of intercropping compared to the monoculture.

The results showed that all studied traits were affected by the planting system. There was a significant interaction between planting system, weeding and density in light absorption, temperature and humidity. The results showed that the absorbed Photosynthetically Active Radiation in the intercropping (75.5%) was higher than the monoculture of both plants. Weed control increased the adsorption of Photosynthetically Active Radiation by 70.75%, and in the twice weeding treatments and low density, the highest amount of adsorbed Photosynthetically Active Radiation was obtained. The highest volumetric soil moisture was obtained in sole peanut (31.1%) and the highest soil temperature was obtained in sole millet (29.66 °C), respectively. Comparison of volumetric soil moisture and temperature in weed and density treatments indicated an increase in moisture content and a decrease in temperature by increasing weeding and density. The reduction of soil temperature in intercropping systems compared to sole millet can be attributed to the greater absorption of light by the intercropping canopy and the increase of shadow by plant canopy. Since the soil temperature under the canopy of intercropping systems was less than the soil temperature in sole millet, so the moisture content in the intercropping systems was higher than sole millet. The results of the changes in soil nutrient elements showed that the number of bivalent elements (calcium and magnesium contents) in additive intercropping series and monoculture of millet (0.033 and 1.907 ppm) was higher than the replacement intercropping and monoculture of peanut. The study of weeding showed that with increasing weeding, the amount of calcium and magnesium of the soil increased after weed harvesting. The cation exchange capacity of the root of the legumes is about twice as much as the root of the cereals. A plant with a higher cation exchange capacity can absorb more bivalent elements. For this reason, the power of peanut competition in absorbing bivalent elements of calcium and magnesium was higher than that of millet. The additive intercropping had the highest land equivalent ratio (1.65). The effect of weed control and density on the land equivalent ratio was significant, and twice weeding treatment with higher density had the maximum land equivalent ratio.

In total, intercropping systems with increasing weeding and density increased the number of soil elements after weeding and increased soil fertility, and treatment of 100% millet + 100% peanuts due to better utilization of resources and increased soil fertility and increase yield compared to monocultures, it was the best treatment in this study.