Overcoming constraints to high yield and CCS in large and lodged cane crops
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Past research indicates that large sugarcane crops (that usually also happen to be lodged) experience a slowdown in growth during winter, well before harvest (Muchow et al. 1996). The project examined factors affecting the growth of crops in both the dry (irrigated) and wet tropics and aimed to interpret and explain the effects of the identified factors on net growth and death processes as well as on the stalk and sucker dynamics, cane yield and CCS. Treatments included installation of bamboo scaffolding to prevent crop lodging, and a late ratooning of the crop so that a physiologically young crop would be growing into the winter ripening period. Experiments were conducted over two seasons (1997-1998 & 1998-1999) in commercial fields in areas where large crops may experience substantial lodging under different environmental conditions (Burdekin and Tully). Four or five sequential harvests were taken to determine if and when growth slowdown occurred and to separate the effects of crop age, season and lodging. By installing scaffolding to prevent lodging, we eliminated the growth ‘slowdown’ in three experiments to confirm that lodging and stalk death is part of the explanation. In both the wet and dry (irrigated) tropics, lodging of sugarcane significantly decreased both cane yield and fresh commercial cane sugar content (CCS). Prevention of lodging increased fresh cane yield by 11 - 15 %, CCS by 3 - 12 % and sugar yield by 15 - 35 % at the final harvest in August/September. The rate of increase in CCS in lodged cane was reduced following lodging, although CCS recovered by harvest to be similar to that of erect cane. While death of stalks was confirmed as a major component of the effect of lodging there was also a reduced weight and sugar content of live stalks. Dead and rat damaged stalks had CCS levels that were regularly less than 50% of sound live stalks. In the dry tropics, where cane is irrigated and grows under high radiation, sugar yield was 40 t/ha with scaffolding installed. The increased yield (compared to 35 t/ha in lodged cane) was due to both the survival of an extra 0.8 stalks/m2 and increased accumulation of sugar in live stalks. These experimental results have been published in two conference papers and in an upcoming issue of the Australian Journal of Agricultural Research (early 2003).