Effect of Nitrogen Fertilizer on Striga Infestation, Yield and Yield Related Traits in Sorghum [(Sorghum Bicolor (L.)Moench] Varieties at Kile, Eastern Ethiopia

Abstract

Striga spp. are considered to be the greatest biological constraint to food production in sub-Saharan Africa. They are among the most specialized root-parasitic plants inflicting serious injury to their host depriving them water, minerals and photosynthesis from the host. Ethiopia is the one among countries facing the challenges of those deadly enemies for sorghum crop production. This problem is also common in the eastern semi-arid area which is one of the most sorghum producing areas of the country including Kile-Bisidimo plain. The objective of this study was to assess the effect of nitrogen fertilizer rates on Striga infestation, yield and yield related traits on three sorghum varieties (Gubiye, Hormat and Teshale) and five nitrogen fertilizer rates (0, 23, 46, 69 and 92 kg N ha^{- 1}) at Kile, eastern Ethiopia in a randomized complete block design replicated three times. Plots treated with N fertilizer had significantly fewer number of Striga at 10, and 12 weeks after planting (WAP), but at 8WAP and at harvest was not significant due to all.  Based on this study, nitrogen fertilizer has the potential to reduce number of Striga per plot while increasing rates from zero to 92kg N ha^-1. Similarly, N fertilizer was significantly affected the plant height, capsules/plant and dry weight/plot.  Nitrogen at 92 kg N ha^-1was significantly more effective in suppressing S. hermonthica than nitrogen at 0, 23, 46 and 69 kg N ha^-1 applied at 10 and 12 WAP.  There was statistically significant difference due to variety on days to 50% flowering, due to nitrogen was not significant. Days to 90% maturity was significantly affected by both. Growth parameter (plant height) was only significant due to nitrogen. Among yield and yield components, stand count was not affected by all.  Productive tillers per plot (12m²) and tiller number per plant were significant for all except nitrogen by variety interaction.  Regarding panicle weight, above ground biomass, grain yield, 1000-kernel weight and harvest index) were significant due to nitrogen and variety, but nitrogen by variety interaction was not significant. Panicle length was significant due to only variety, but others were not.  With regard to economic analysis application of 92 kg ha^-1was gave the highest gross benefit (45,402.48 ETB ha^-1) whereas the lowest gross benefit (22,217.76 ETB ha^-1) was obtained under no N treatment. The highest net benefit (31,535.84 ETB ha^-1) was obtained with 92 kg N ha^-1 application while the lowest net benefit (15,495.76 ETB ha^-1) was from no N application. Marginal rate of return was positive for all N rates. The percentage gain from 46 to 69 kg N ha^-1 is better as compared to the gain from 0 to 23 kg N ha^-1, 23 to 46 kg N ha^-1 and 69 to 92 kg N ha^-1.  The economic analysis has led to 69 kg N ha^-1 when compared to 0, 23, 46 and 92 kg N ha^-1 as suitable for potential adoption by farmers.

Keywords:  Nitrogen, soil characteristics, S.hermonthica, Yield components of sorghum