Evaluation of Forage Quantity and Quality of Barley (Hordeum vulgare L.) and Pea (Pisum sativum L.) Intercropping System in Maragheh Rainfed Conditions

Intercropping can provide numerous benefits to cropping systems through increasing total yield and land use efficiency, improving yield stability of cropping systems, enhancing light, water, and nutrient use, improving soil conservation and controlling weeds, insects, or diseases. Moreover, intercropping can facilitate mechanical harvest, whereas legumes in mixtures with cereals can improve the quality of forage. Although cereals are widespread used in livestock nutrition for their high dry matter production and low cost, they have low nutrition value due to their poor protein content. High quality of forage has been notified as an important aspect of forage crop production.

The experiment was conducted at the faculty of Agriculture, university of Maragheh, Iran as factorial based on randomized complete block design (RCBD). The first factor were 100, 150, 200, 250 and 300 plants m-2 of field pea and the second factor were different intercropping patterns based on substitution ratio (25% barley+75% filed pea, 50% barley+ 50% filed pea and 75% barley+ 25% field pea). At harvesting time quantity and quality properties including total forage yield neutral detergent fiber (NDF), acid detergent fiber (ADF), crude protein (CP) and ash were determined. Also, the land equivalent ratio (LER) is defined as the land equivalent needed for growing either crops in intercropping systems compared with the land area needed to each crop monocultures. The LER values were calculated as:(Eq.2) Where LER and LERs were land equivalent ratio and standard land equivalent ratio, respectively; Ypp and Ybb were yields of field pea and barley monoculture; and Ypb and Ybp were yields of field pea and barley in intercropping patterns. Analysis of variance of the data and mean comparison based on Duncan’s multiple range test were carried out using MSTATC statistical software.

The results showed that the total forage yield was significantly affected by different planting patterns and densities. The highest total forage yield was obtained under 75% barley+ 25% forage pea followed by 50% barley+ 50% forage pea. Also, the lowest total forage yield was observed under 25% barley+ 75% field pea. In Addition to, densities of 100 and 300 plants m-2 of field pea had the highest and lowest effect on total forage yield.  The higher forage production may be due to higher resource use complementarity in time and space between intercropping components. In terms of forage quality, ash forage decreased with increasing proportion of barley. Thus, under 75% barley+ 25% forage pea the forage ash amount decreased 23.85 and 17.38% in comparison to 25% barley+ 75% forage pea and 50% barley+ 50% forage pea. Concentration of the total crude protein enhanced by increasing proportion of forage pea in intercropping. Therefore, the highest percent of the total crude protein was obtained under 25% barley + 75% forage pea with density of 300 plants m-2. In addition,  the content of neutral detergent fiber (NDF) and ADF significantly decreased with increasing proportion of forage pea. Forage quality improvement in terms of higher crude protein and lower NDF and ADF were attributed to presence of the legume species in intercropping patterns (Stolts & Nadeau, 2014). In most treatments, the LER values were >1, which suggests an overall yield advantage of intercropping compared with monoculture. 

Our trials exhibited that, the highest total forage yield was obtained under 75% barley+ 25% forage pea. NDF and ADF increased with enhancing proportion of barley. So that, the highest and the lowest ADF and NDF content were obtained under 75% barley+ 25% field pea and 25% barley+ 75% filed pea, respectively. The highest LER (1.25) was achieved under 25% barley+ 75% field pea (with density of 100 plants m-2). Generally, barley intercropping with forage pea in lower densities can improve forage production under rainfed conditions