Effect of Nitrogen Fertilizer Types and Microelements on Growth, Yield and Chemical Constituents of Tuberous Root of Sweet Potato (Ipomoean batatas L, Lam)

In this study, the effect of nitrogen fertilizer types, micronutrients mixture concentrations foliar application and their
interactions on growth, yield of tuberous root and chemical characteristics of sweet potato were investigated. The
treatments included four nitrogen fertilizer types; 60 kg fed.-1 (full recommended dose of mineral N fertilizer) ;15 kg fed.-1
mineral N fertilizer (1/4 recommended dose) + 1.5 m3 compost fed.-1; 30 kg N fed.-1 mineral N fertilizer ( 1/2
recommended dose) + 1 m3 compost fed.-1 and 45 kg fed.-1 mineral N fertilizer (3/4 recommended dose)+ 0.5 m3 compost
fed.-1. Four foliar application of micronutrients mixture concentrations (0, 10, 20 and 30 g 100 l-1 H2O). The obtained
result indicated that application of full recommended dose of mineral N fertilizer significantly increased plant length,
number of branches, vine fresh weight, root length, root diameter, number of root plant-1 and total yield characters.
However 15 kg fed.-1 mineral N fertilizer (1/4 recommended dose) + 1.5 m3 compost fed.-1 or 30 kg fed.-1 mineral N
fertilizer (1/2 recommended dose) +1 m3 compost fed.-1 gave the highest mean values of total sugars, starch, root dry
matter and carotene. Moreover, micronutrient at 30 g 100 l-1 increased significantly all the vegetable and yield characters.
The best results on vegetative growth, yield and chemical constituents were achieved when sweet potato plants fertilized
with full recommended N and foliar application with 30 g 100 l-1 micronutrient.