Inter-Annual Coefficient Of Variation (%) Dryland Sugarcane Yield

South Africa is ranked 13th in the world (SA Yearbook, 2005) as a producer of sugarcane, Saccharum officinarum. Average sucrose content of the South African crop is approx 13.5%, varying from 11.9 - 13.8% and inversely related to the year`s rainfall. It takes approximately 8.5 tonne sugarcane to produce 1 t sugar, varying from 8.3 - 10.0 t (SASA, 2005). Of the cane under irrigation, 72% is in KwaZulu-Natal (mainly Pongola and Mfolozi flats) and the remaining 28% in Mpumalanga (Statistics SA, 2002). 95% of the sugarcane crop is fertilized and this accounts for 18% of the fertilizer use in South Africa (FAO, 2005). Estimation of Sugarcane Yield was with the ACRU-Thompson Model equation which related sugarcane water use (total evaporation) to yield as Ysc = 9.53(Ean / 100) - 2.36 and where Ysc = annual sugarcane yield (t/ha), and Ean = annual total evaporation (mm).