Effect of the Time and Rate of N-Fertilizer Application on Growth and Yield of Wheat (Triticum aestivum L.) at Gamo-gofa Zone, Southern Ethiopia

There is little knowledge among farmers on the time and rate of N-fertilizer application at Gamo-gofa. Therefore, there is a need to determine time and rate of N-fertilizer application on growth and yield of wheat. Accordingly, an experiment were conducted to evaluate the effect of the time and rate of N-fertilizer application on yield and yield components of wheat on two locations at Gamo-gofa, Southern Ethiopia in 2014 and 2015 cropping season. A factorial combination of the time (at planting, 15 and 30 days after planting) and rate (0, 23, 46, 69 and 92 k.gha-1) of N-fertilizer application were arranged in split plot. Time and rate of N-fertilizer and their interaction had significantly affected days to heading, plant height, number of tiller, panicle, thousand seed weight, grain, straw and total biomass yields. Also year and location had significantly affected days to maturity and spike length. Whereas location had significantly affected days to heading and spike length; but year had significantly affected plant height, biomass, straw yield, thousand seed weight and grain yield. Meanwhile time and rate of N-fertilizer and there interaction, and location had not significantly affected days to maturity and harvest index; but year had significantly affect. The additive effect of fertilizer applied with the rate of 23, 46, 69 and 92 kg ha-1 at thirty days after planting; minimize the date of heading by six days compared with fertilizer applied at the time of planting in the rate of 0, 23, 46 and 69 kg ha-1. Planting at Bonke woreda had hastened the day for heading by one day compared with planted at Chencha woreda. Wheat planted in 2014 was delayed the date of maturity by twenty days compared with planted in 2015. Planting of wheat at Bonke woreda hasted the day for maturity by nineteen days compared with planting at Chencha woreda. The additive effect of 69 kg ha-1N-fertilizer applied at thirty days after planting had contributed for 16.5 cm in increments in height than control. Wheat which, planted in 2014 had 6.8 cm more plant height than planted in 20015. Fertilizer applied at fifteen days after planting with the rate of 46 kg ha-1 was decrease spike length by 3.8 cm compared with fertilizer applied at thirty days after planting with the rate of 46 kg ha-1. The additive effect of fertilizer applied thirty days after planting with the rate of 23 kg ha-1had 70.3 % more tillers than control, but 12.4 % less tillers than fertilizer applied thirty days after planting with the rate of 46 kg ha-1. Fertilizer applied 69 kg ha-1 at thirty days after planting contributed to 28.6 % increment in biomass than fertilizer applied 92 kg ha-1at thirty days after planting. Fertilizer applied 92 kg ha-1 had 57.8 % less straw than fertilizer applied thirty days after planting with the rate of 69 kg ha-1. The combined effect fertilizer applied 69 kg ha-1at thirty days later of planting had 19.2% more thousand seed weight than control. Fertilized applied at fifteen days after planting with rate of 23 kg ha-1had 25.5 % more grain yield than control; but 7.5 % less grain yield than 69 kg ha-1 N fertilizer applied at thirty days after planting. Wheat planted in 2015 had 37 % less harvest index than which, planted in 2014. Thus, 23 kg ha-1 fertilizer applied at thirty days after planting is economically beneficial compared to the other treatments. Keywords: Time of fertilizer application; Rate of fertilizer, Fertilizer, Nitroge