Effect of Soybean Varieties and Nitrogen Fertilizer Rates on Yield, Yield Components and Productivity of Associated Crops Under Maize/Soybean Intercropping at Mechara, Eastern Ethiopia
Due to decreasing land units and decline in soil fertility integrating soybean in to the maize production system is a viable option for increasing productivity and protein source. In view of this, field experiment was conducted during 2012 at Mechara Agricultural Research Center with theobjectives of identifying best compatible combinations of maize with soybean varieties and N rates for maximum yield and yield components of the associated cropsand productivity of intercropping system. Three varieties of soybean (Awasa 95, Cocker 240 and Crowford) were intercropped with early maturing maize variety Melkasa 2 with three rates of nitrogen (32, 64 and 96 kg N ha 1) The experiment waslaid out in factorial arrangement in randomized complete block design in three replications. Highest maize grain yield (2196kg ha 1) was obtained from soybean variety Crowford and 32 kg N ha 1 and lowest yield (1352 kg ha 1) was recorded from maize intercropped with soybean variety Awasa 95 at 96 kg N ha 1. The grain yield of intercropped soybean was increased from 586 kg ha 1 to 842kg ha 1 as the nitrogen rates increased from 32 kg N ha 1 to 96 kg N ha 1. The higheist LER (1.10) was obtained from maize intercropped with soybean variety Crowford and lowest LER (1.08) was from maize intercropped with variety Cocker 240 due to main effects of soybean varieties while due to main effects of N, the highest (1.16) and the lowest (1.1) LER were obtained from higher rate of nitrogen (96 kg N ha 1) and lowest rate of nitrogen (32 kg N ha 1) respectively. On the other hand, the highest Gross Monetary Value (17315 Birr ha 1) was recorded from interaction of Cocker 240 at highest rate of nitrogen (96kg N ha 1) which was not significantly different from Awasa 95 at 32 kg N ha 1 (15304 birr ha 1) and Crowford at 32 kg N ha 1 (15103) while lowest GMV (12362birr ha 1) was obtained from variety Cocker 240 at 32 kg N ha 1. Therefore, variety Awasa 95 at lower rate of nitrogen (32 kg ha 1) could be best in intercropping system to reduce cost of fertilizer and maximize total productivity.