Effect of Cutting off Irrigation on Yield and Competition and Economic Indices of Intercropping Barley (Hordeum spp.) with Legumes

Intercropping is an old and widespread practice used in low input cropping systems in many areas of the world. Intercropping systems, especially those employing cereals with legumes, have several major advantages such as higher total yield and better land use efficiency yield stability of the cropping system, better utilization of light, water, and nutrients. The reasons for the higher yield in such systems is that the intercropped species do not compete exactly for the same growth resource niche and thereby tend to use the available resources in a complementary way. Several indices such as land equivalent ratio (LER), competitive ratio (CR), aggressivity (A), actual yield loss (AYL), and intercropping advantage (IA) have been developed to describe the competition and the economic advantage in intercropping. With respect to drought stress in late season of Sothern Iran and the importance of intercropping to reach stability and sustainability in production, the aim of this study was to assess the changes in yield and competition and economic indices of intercropping barley with legumes under late season drought stress.

A field experiment was conducted to evaluate the competitive and economic indices of intercropping barley cultivars with pea and fababean under different irrigation regimes at College of Agriculture and Natural Resources of Darab, Shiraz University during 2014 growing season. Treatments were included two levels of irrigation regimes (full irrigation and cutting off irrigation at milk development of barley) and 8 cropping treatments consisted of monoculture of Nimroz tow-rowed barley, Zehak six-rowed barley, pea and fababean and intercropping of Nimroz+pea, Nimroz+fababean, Zehak+pea and Zehak+fababean with a ratio of 1:1 which laid out as split plot arrangement in randomized complete block design with three replicates. Competitive and economic indices were including land equivalent ratio (LER), competitive ratio (CR), aggressivity (A), actual yield loss (AYL), intercropping advantage (IA), and system productivity index (SPI). Analysis of the variance was performed using MSTATC ver 2.10 software (1991) and the mean comparisons were performed by LSD test at 5% probability level.

Analysis of variance showed that irrigation regimes and cropping treatments had significant effect on barley and legume yields, LERtotal, Atotal, SPI, CR, AYL total, and IAtotal. Cutting off irrigation, decreased 20, 43 and 40% barley cultivars, pea and fababean yield, respectively and increased 1.9, 42 and 20% LER of cereals, legumes and total, respectively. Also, under cutting of irrigation, intercropping of Zehak+pea had the lowest yield loss (13%) while Zehak+fababean had the highest yield loss (27%) among the intercropping treatments. A and CR indices showed that in full irrigation conditions, barley cultivars were dominant species and at drought stress condition competitive power of legumes increased. In full irrigation, actual yield loss indices of barley cultivars, legumes and total was positive, negative and zero, respectively and intercropping advantage indices of barley cultivar was positive and in legumes and total was negative. Likewise, AYL and IA indices, in cereals, legumes and total were positive. The maximum grain yield in barley cultivars, pea and fababean was obtained at sole cropping treatments, while LER of all intercropping treatments was higher than 1. SPI for all of the intercropping treatments was positive.

Evaluating competitive and economic indices showed that intercropping systems of six-rowed Zehak barley cultivar with pea was advantageous than sole cropping system under drought stress condition because of betterland use efficiency and better economics than the other mixtures examined. This mixture could be economically and environmentally promising in the development of sustainable crop production and thus can be adopted by farmers for maximization of economic yields especially under drought stress condition