Muhammad Kadwa1, Louis W Titshall2 and Richard J Nicholson1
1South African Cane Growers Association, Mount Edgecombe, South Africa; Muhammad.Kadwa@sacanegrowers.co.za
2South Africa Sugarcane Research Institute, Mount Edgecombe, South Africa
Current fertiliser nitrogen (N) recommendations aim to provide near maximum yields, rather than optimal revenue returns. However, recent surges in fertiliser prices resulted in many growers seeking short-term advice on reducing N-rates without compromising profitability. Unfortunately, variability in responses to N application makes it difficult to provide clear, site-specific guidelines on adjusting N-rates. A simplistic economic analysis was used to examine the sensitivity of N-fertiliser application and costs for a single season, compared with cane income, using ratoon-crop response data from research trials. Sugarcane and sucrose yield data from several N trials undertaken by SASRI in the last 15 years were used for this study, for irrigated and rainfed growing regions. Due to the South African sugar industry using the Recoverable Value (RV) for cane payments, sucrose and cane yields were converted to approximate RV yields with gross income estimated at three RV Price levels. The cost of N-application was zero for untreated control treatments and assumed the same for all other N-rates. Income comparisons were made with low, median and high N prices over three recent years. The results indicated that the RV price level does not change the rates of N application for the irrigated region, whilst there was considerably more variability in the rainfed results. Growers should consider both the RV and N price when determining the N-rates. Furthermore, the longer-term impacts on subsequent ratoons, of any reduced N application, should also be considered. This analysis provides simple snapshot advice for growers in terms of N application rates at different RV Price and N price levels. This study used research trials, thus there would be value in undertaking commercial-scale tests with growers’ operations, to help guide site-specific guidelines. Other fertiliser elements can be analysed in future work.