Contribution of first and second year growth to the yield of two-year cane in NSW

Sugarcane production in NSW is mainly based on two-year crop cycles primarily because of the relatively small amount of growth in the first 12 months. This paper analyses the yield accumulation processes during the first and second year using data from a field experiment at Harwood comparing two varieties, grown under both highinput "potential yield" and "commercial" conditions. Cane and sucrose yield more than doubled in the second year (at 22 months) compared to the first year's growth. Yield accumulation per unit time was more efficient in the second year but physiologically was less efficient in the second year with calculated average radiation USe efficiencies decreasing from 1.23 to 0.90 glMJ. At 12 months, the partitioning of stalk biomass to stalk sucrose was similar to that recorded in studies elsewhere in north Queensland and Hawaii. The low sucrose concentration on a fresh weight basis at 12 months was a consequence of low biomass and low stalk dry matter content. However, at 22 months, stalk sucrose concentration on a dry weight basis was much lower than that expected for the accumulated stalk biomass. It is concluded that there is considerable scope for increasing commercial yields in the NSW environment but that partitioning of stalk biomass to stalk sucrose is less efficient in the second year of growth. This problem appears to contribute to low CCS in NSW and merits further investigation.