Evaluation of effect of coated fertilisers for use in flue-cured tobacco production
Two coatings, one which coats phosphate known as Avail and another called Nutrisphere-N which coats nitrogen, were used. Avail lengthened phosphate availability by protecting the phosphates from being locked up by Fe, Al, Mg and Ca. Nutrisphere-N controls loses of nitrogen by reducing volatilisation, slowing the conversion of ammonia into nitrate, which reduces de-nitrification and leaching. Experiments were conducted for two seasons to evaluate the performance of coatings on growth, yield and quality of flue-cured at Kandiya, Mwimba and Kabwafu Research Stations. The design was randomised complete block with four replications. The Avail coated SuperD and Nutri-sphere coated Urea were each tested for yield and quality at rates of 100%, 90%, 75% and 50% over the Malawi recommendation (nine by 50 kg bags/ha of non-avail coated SuperD top-dressed with two by 50 kg bags/ha calcium ammonia nitrate (CAN)). Two controls: SuperD (N10.5%:P24%:K20%) as basal and CAN (27%N: 0P:0K) as top dressing fertiliser, the second control, Nil treatment. Results showed that coatings had positive influence on yield and quality over non-coated. Avail coated SuperD at reduction rates of 75% (75AP+C) or at 50% (50AP+C) top dressed with CAN produced higher yields and good quality tobacco across three sites. Regardless of the coatings, the Malawi recommended rate was out-performed by 24% on yield and 61% on first grade leaf. The coatings produced larger root volumes, taller plants, larger stem diameters and improved leaf characteristics, but those with Avail had an advantage over the Nutrisphere ones, it was evident that the coated fertilisers had an edge over the Malawi non-coated fertilisers. Coated SuperD when used together with CAN at reduced rates of up to 50% improves yield and quality of flue-cured tobacco. The coated fertilisers with savings of up to 50% over the non-coated amounts have significant potential savings on costs of fertilisers.