Evaluation of Growth Indices Advantages in Intercropping of Green Bean and Basil

Intercropping of basil with legumes due to morphological differences and more importantly, their biological stabilization can be a step towards sustainability in agriculture and also to avoid the use of chemical inputs and therefore produce healthier products. Therefore, the objectives of this experiment were to evaluate and compare different indicators of growth, yield and ecological and economic usefulness of basil with green bean in pure crops and mixed replacement ratios in Mashhad climatic conditions.

An experiment was conducted in RCBD design at the research farm of Ferdowsi University of Mashhad in the growing year 2018 19. The treatments were: 1) sole cropping of green bean (P), 2) and also basil (O) and different ratios of intercropping of these two plants, including 3) 1:3 ratio of green bean and basil (P1O3), 4) ratio 2:2 green bean and basil (P2O2) and 5) 3:1 ratio green bean and basil (P3O1). Daily values of growth indices during the growth period of plants were estimated using the specific functions, and at the end of the growing season, the final yield of intercropped species (fresh green pods of green bean and basil dried seeds) was measured and indicators related to the advantage of intercropping including land equivalent ratio (LER), actual yield loss (AYL) and the monetary advantage index (MAI) were calculated. Function fitting, statistical analysis of data and drawing of figures were performed using Slide Write ver2.0, SAS v 9.2 and MS Excel 2016, respectively.

The highest LAI recorded in sole cropping of green bean and basil (3.4 and 3 respectively) and the lowest was for green bean in P1O3 (0.2) and for basil in P3O1 (2). Also, highest TDM in sole cropping of green bean was 973 g m2 and in sole cropping of basil was 1654 g m2 and the lowest ones for intercropped green bean was in P1O3 (44 g m2) and in the intercropped basil in P3O1 (755 g m2). The highest CGR of green bean and basil in their sole cropping were 20.56 and 17.92 g m2 day-1, respectively. The mean RGR of green bean was 0.03 g g-1 in P1O3 and the highest RGR was in basil in the sole cropping treatment (0.03 g g-1) The highest NAR in green bean was in its sole cropping (8.3 g m2 day-1) and basil (8.5 g m2 day-1). No economic yield was achieved for green bean in P1O3 and P2O2 treatments, so all the advantage indices of intercropping including LER, AYL and MAI in these treatments were negative. Also, the highest yield of basil was obtained in P1O3, which was not significantly different from its sole culture, and only in this treatment the intercropping advantage indices studied were positive and preferred to sole culture.

The results truly showed incompatibility of basil with green bean in intercropping due to low competitiveness and weakness of green bean in intercropping with basil. Although intercropping in P3O1 treatment was economically and ecologically beneficial, but by considering all the conditions such as the possibility of implementing this cultivation ratio, it is suggested that while examining more different aspects of intercropping of basil with green bean such as weed competition and mechanisms of basil competition with green bean, another legume crop that has more desirable characteristics in terms of ecological compatibility and non-interference of ecological niches with this plant to replace green bean in basil production systems.