Effect of Cowpea Intercropping Date in Maize and Sorghum Fields on Productivity and Infestation Weed

TWO FIELD experiments were carried out at Malawi Agricultural Research Station, Minia Governorate, Egypt during 2008 and 2009 summer seasons, to study the effect of cowpea intercropping date on maize (the first one) and sorghum (the second one) on productivity and associated weeds. Three intercropping dates of cowpea with maize or sorghum were three weeks preceding (D1), synchronized plantation (D2) and post maize or sorghum plantation with three weeks (D3) as well as the solid plantation of the three crops. The results indicated that cowpea intercropping date significantly affected plant heights of either maize or sorghum. The preceding cowpea intercropping (D1) significantly decreased maize and sorghum plant height while neither (D2) nor (D3) had shown significant effects on plant height. The grain yields of both maize and sorghum were remarkedly reduced by 50.4 and 36.6% with preceding cowpea intercropping, respectively, while the post plantation cowpea intercropping (D3) tended to insignificant increase the grain yield of maize or sorghum. Effective reduction reached 90% and 93.7% of weed biomass when maize and sorghum were intercropped with cowpea at the same time (D2), respectively. The post plantation cowpea intercropping with maize and sorghum caused less weed biomass reductions reached 65.5% and 80.6%, respectively. Green forage yield of cowpea overall cuts was decreased as the results of post plantation cowpea intercropping (D3) than the other two dates (D1 and D2). The reduction was 63.4 and 70.2% when cowpea as compared with solid cropping of cowpea was intercropped with maize and sorghum, respectively, while, the reduction diminished to 27.5% and 32.4% when the preceding cropping of maize and sorghum was applied. Maize and sorghum were the dominant crops, whereas cowpea was the dominated one. The highest land equivalent ratios recorded 1.4 when cowpea intercropped three weeks after maize (D3) and 1.5 for synchronized cowpea intercropping (D2) with maize and sorghum, respectively. The most benefit realized was associated with post plantation cowpea intercropped with maize expressed as monetary index of 1840.63. The total actual yield loss was negative in the three intercropping dates with maize or sorghum which decrease in yield of these crops compared with solid state. It could be concluded that synchronized cowpea intercropping (D2) with maize and sorghum is the most profitable and preferred for reducing weed infestation.