Abstract

Kiran Pavuluri, Zacharia Malley, Mohamadi K Mzimbiri, Timothy D Lewis, 2Robert Meakin

Recent exploration of new multi-nutrient potassium fertilizers such as polyhalite and a lack of understanding of their effects on corn grain yield performance motivated establishing six corn (Zea mays L.) fertilizer trials in the Southern Highland region of Tanzania, under rain-fed conditions, in 2015. The objective was to determine whether applying 20 kg ha-1 of K2O from two different sources together with the recommended practice of 120 and 30 kg ha-1 of N and P2O5, respectively, with no K2O, increases corn grain yields. Fertilizer treatments were: 1) Control in which no fertilizer was applied; 2) Recommended practice of 120 and 30kg ha-1 of N and P2O5(NP); 3) NP + 20 kg ha-1 of K2O as Muriate of Potash (MOP); 4) NP + 20 kg ha-1 of K2O as Polyhalite (POLY4); and 5) NP + MOP + 28 kg S ha-1 as Kieserite (MOP + Kieserite). Kieserite was applied at a rate to balance the S applied in the POLY4 treatment. Measured variables were grain yield, stover weight, number of cobs, vigour and plant populations. Treatments of interest were compared by using single degree freedom linear contrasts. All fertilizer treatments significantly outperformed the Control at all locations. The NP, POLY4 and MOP+Kieserite treatments had significantly higher grain yields than MOP at one, two and two out of six locations, respectively. Similarly, NP, POLY4 and MOP+Kieserite treatments had numerically higher grain yields at four, five and five locations, respectively over MOP. When averaged across the six locations, NP, POLY4 and MOP+Kieserite treatments had grain yields 357, 621 and 662 kg ha-1 higher than MOP, respectively. These results indicate the importance of sulphur nutrition for corn and that POLY4 is a source of sulphur and potassium for corn production in the Southern Highland regions of Tanzania