Growth and sugar accumulation in one and two year crop cycles in New South Wales

Growth and sugar accumulation were studied in 50 clones grown in oneand two-year crop trials at Harwood in New South Wales. Average cane and sugar yield responses during the second year were similar for the one-year (plant plus first ratoon crops) and two-year trials, but total cane apd sugar yield was marginally higher in the two-year trial. In both cases, the major growth was from October 1991 to May 1992, with little increase from May to September 1992 due to dry conditions. The best five clones were chosen (or each of the two crops, based on total sugar production at optimum harvest times. Cane and sugar yields in the first year were considerably higher for the best one-year trial clones, but the best two-year clones gave higher total, prodwction over .the two years up until SeptembeL A notable feature of the best clones in the twoyear, trial was their lack of growth from June to September in' the first year. Another feature of the best two-year clones was the high contribution of oneyear stalks to total cane and sugar yields. One-year stalks of the best two twoyear clones contributed cane yields of 120 t/ha and sugar yields of 16 t/ha, representing 36 % of the total.