EFFECT OF APPLYING HUMIC ACID AND FOLIAR FERTILIZATION WITH POTASSIUM ON GROWTH AND YIELD OF Zea mays L

A factorial experiment was conducted in clay loam soil at a farm belonging to Salam city, 25 km northeast of Baquba during autumn season 2015, to study the effect of applying humic acid and foliar fertilization with potassium and their interaction on growth and yield of maize (Zea mays L.), synthetic variety 5018 was used. Randomized Complete Block Design (R.C.B.D) with three replications was used. Four levels of humic acid (0, 0.5, 1, and 2 g m-2), and four levels of potassium (0, 1000, 2000, and 3000 mg K l-1 as potassium sulfate 41.5 % K) were used. The results showed that humic acid 2 g m-2 had a significant effect on plant height which gave 204.866 cm, leaf area 588.120 cm2, chlorophyll index 55.213 SPAD, the weight of 500 grain 154.096 g, and plant yield 256.356 g plant-1. While spraying with potassium at a concentration of 3000 mg K l-1 gave the highest plant height 205.000 cm, leaf area 585.933 cm2, chlorophyll index 54.904 SPAD, the weight of 500 grain 153.645 g, and plant yield 253.072 g plant-1.