Assessment of Calcium Nitrate Fertilizer as a Suitable Nitrogen Source for Cacao (Theobroma cacao L.) Cultivation in Ghana

Abstract

Urea or sulphate of ammonia fertilizer application on cacao (Theobroma cacao L.) in Ghana has either caused no changes or a decrease in cacao yields. In Ghana, soil diagnosis has shown low soil N in cacao-growing areas, which could be limiting cacao production. Alleviating the low soil N to increase cacao yields without negative effects requires the use of an appropriate source and dose of N fertilizer. A study was conducted to determine the suitability of calcium nitrate fertilizer as a source of N and the right N dose that will ensure an increase in cacao yield. A randomized complete block design with three replications was used to evaluate the effects of 11 treatments which were combinations of dose and number of N fertilizer application. The results showed an increase in soil pH, N, and P contents and a decrease in exchangeable bases over the four years for the surface soil depth. For organic carbon (OC), the average annual rate of change resulted in a gain of OC in the soils for all the treatment plots, except for treatment with 60 kg N ha−1 applied once over the 4 years. Soil P concentrations of the plots saw a drastic increase and a gain of P for all the treatment plots. The concentration of exchangeable bases declined in 4 years. Significant differences were observed in the 3-year cumulative dry bean yield of cacao for the treatments with 75 kg N ha−1 split applied being the highest. The study showed that the calcium nitrate fertilizer is a suitable N source for cacao in Ghana and a dose of 75 kg N ha−1 of the fertilizer should be split applied, i.e., half applied in May and half applied in September to ensure an increase in cacao yield.