The effects of nitrogen levels and intercropping pattern on forage yield and competition indices of barley (Hordeum vulgare) and pea (Pisum sativum)

Background and objectives
Intercropping or simultaneous growing of two or more crops on the same piece of land has the potential of enhanced ecosystem productivity. In a cereal-legume intercropping system, an increase in cereal and a decrease in legume intercrop yield is reported. Several indices such as land equivalent ratio (LER), relative crowding coefficient (K), competitive ratio (CR), aggressivity (A), actual yield loss (AYL) and intercropping advantage (IA) will be used to describe the competition and the economic advantage in intercropping. The objectives was to study the effect of nitrogen fertilizer and intercropping pattern on forage yield and competition indices of land equivalent ratio, relative crowding coefficient, aggressivity, competitive ratio, actual yield loss, intercropping advantage, equivalent yield and system productivity index.
Matherials and Methods
This experiment was arranged as factorial layout based on a Randomized Complete Block Design with three replications at the research farm of Gonbad Kavous University during growing season of 2011- 2012. Two factors were five planting patterns including monoculture of barley, 25, 50 and 75% pea replacement of barley and monoculture of pea and four nitrogen levels of control and 25, 50 and 75 kg N ha-1.
Sowing date was 29 Novebber 2011 and plants harvested at 26 April 2012. The traits were forage dry yield and indices of land equivalent ratio, relative crowding coefficient, aggressivity, competitive ratio, actual yield loss, intercropping advantage, barley equivalent yield of pea and system productivity index. For analysis variance of data software of SAS Ver.9.1.3 were used and treatment mean differences were separated by the least significant difference (LSD) test at the 0.05 probability level.
Results
The results showed that monoculture of barley had maximum forage yield with 17.16 ton ha-1. By reducing for barley in intercropping ratio, forage yield was reduced so that minimum yield obtained from 25% barley + 75% pea with 9.62 ton ha-1. Monoculture of pea had minimum yield with 6.71 ton ha-1. Forage yield increased by increasing of nitrogen consumption. Land equivalent ratio for total intercropping ratios were less than 1, this indicated that intercropped barley with pea was not suitable. Relative crowding coefficient, Competitive Ratio and Aggressivity for barley in intercropping ratios were greater than pea. Intercropping had not economic benefit.
Conclusion
Forage yield and barley equivalent yield in monoculture of barley and intercrop treatments was greater than pea. Nitrogen consumption increased forage yield and barley equivalent yield. Land equivalent ratio, relative crowding coefficient, aggressivity, competitive ratio and intercropping advantage in barley was better than pea. Actual yield loss in barley was positive and in pea was negative. system productivity y index in 25% instead of barley was higher than two other intercropping treatments.