The Effect of Planting Pattern and Vermicompost on the Changes in Soil Nutrients and Use of Environmental Resources in Intercropping of Corn (Zea mays L.), Peanut (Arachis hypogaea L.) and Borage (Borago officinalis L.)

  In the corn and peanut intercropping system, the organic amounts of carbon, nitrogen, sodium, potassium, calcium and magnesium in the soil were affected by sowing system after harvest and changes in each element varied according to the percentage of plant and different morphological structure between two plants. Intercropping of Roselle and mung bean was modeled based on different percentages of mix-culture and the results showed that, by increasing the cultivation area of Roselle would cause negative effects on soil properties and increasing in the mung bean cultivation area in comparison with the Roselle had a positive effect on the amount of nitrogen and carbon. To determine the best intercropping patterns and effect of vermicompost in corn, peanut and borage intercropping, a split plot test based on randomized complete block design with three replications was conducted at the Institute of Zabol University in 2015. The study factors consisted of various proportion of vermicompost as a major factor in three levels, including: 0, 2.5 and 5 tons per hectare, different patterns of intercropping as a sub-factor in 9 levels including monoculture of corn, peanut, borage, and mix cultivation which are including: 50% corn plus 25% peanut plus 25% borage, 100% corn plus 50% peanut plus 50% borage, 40% corn plus 30% peanut plus 30% borage, 100% corn, 75% peanut plus 25% borage, 60% corn plus 20%peanut plus 20% borage plus and 100% corn plus 25% peanut plus 75% borage. Soil sampling was conducted after harvesting three plants. Soil elements including organic carbon, phosphorus, nitrogen, potassium and sodium were measured in soil sampling. The effects of intercropping patterns and vermicompost on the amount of carbon, nitrogen, phosphorus, potassium, and sodium in the soil were significant at 1% probability level. Statistically, the mutual interaction between these two treatments also showed a significant effect on the amount of the elements. In the analysis of intercropping patterns, the cropping patterns of %100 corns plus %50 peanut plus %50 borage, and the use of 5 ton vermicompost per hectare resulted the maximum amount of organic carbon (%41). By increasing the amount of peanuts to %50 in the cropping pattern, the amount of carbon also increased and in the pattern with the least peanuts percentage, the amount of the element (carbon) decreased. The different root system among three plants, and their competition to absorb more of soil nutrients. The legumes in intercropping with positive effect increased the amount of phosphorus. Among different patterns of intercropping, the least amount of sodium in the soil (8.2m.e.l-1) was observed in %100 corn plus %25 peanut plus %75 borage treatments, while fertilizers were not used. As a result, by increasing borage percentage, the amount of sodium in the soil decreased. The highest yield rate of corn (17.3 t.ha-1) was observed in the intercropping pattern of % 100 corn plus %25 peanut plus %75 borage, and the highest yield rate of peanut (15.5 t.ha-1) was observed in the intercropping pattern of %100 corn plus %75 peanut plus %25 borage and usage of 2.5 ton vermicompost per hectare, and finally the highest performance rate of borage was observed in sole crop, and the use of 5 ton vermicompost per hectare. Furthermore, due to the physiological and morphological differences among the three plant species, the use of environmental resources efficiency in pattern designing increased in intercropping. The Land Equivalent Ratio (LER) of all the intercropping patterns was more than 1, which showed the advantage of intercropping over sole crop. Not only does choosing a suitable planting pattern increase the diversity in agricultural ecosystems, but also it plays an important role in both soil reclamation and protection. Both selection of plants and determination of appropriate intercropping percentages in a pattern are possible with respect to the reduction of competition between species and achievement of multiple ecological, economical, and agricultural goals. According to the results, intercropping pattern including %100 corn plus %50 peanut plus %50 borage, increased amount of organic carbon, nitrogen, and moisture in non-fertile soils and dry lands, hence it was the best model