Asian Research Journal of Agriculture

Carrot (Daucus carota L.) is normally grown under irrigation system. In Tanzania, carrot productivity is still low, mainly due to poor agronomic practices as a result of limited information on optimal levels of irrigation water that enhance crop production. Thus, a study was conducted to evaluate the interactions between various irrigation levels under drip irrigation and soil-based NPK fertilizer for optimal growth, yield, and sugar content of carrots in Morogoro, Tanzania. The crop water requirement was calculated in terms of crop evapotranspiration (ET_c) as the product of ET_o, Kc, and the ground cover reduction factor (K_r). Soil-based fertilizer was applied at a level of 150 kg NPK ha^-1, while irrigation levels applied were 100, 80, and 60% of ET_c. It was found that the growth, yield, and sugar content of carrots were affected differently at various irrigation water (IW) application levels. The growth parameters of carrots improved consistently to optimum IW levels. Further, the highest yield of 33.0 tons ha^-1 of carrots was obtained under 100% of IW, and the lowest yield of 18.47 tons ha^-1 was obtained at 60% of IW. The 60 and 80% IW level yields did not differ significantly (p>0.05). Carrots grown at a deficit irrigation water level of 80% were found to have the highest content of sugar. Therefore, for optimal growth and yield, an irrigation level of 100% is recommended for carrots. However, for high sugar content, an irrigation level of 80% is recommended.