Intra-field variation of commercial cane sugar (ccs) values

Significant intra-field vanatlOn in ccs frequently occurs, but has not been explained to date. or well accepted by Australian canegrowers. This often results in difficult public relations exercises for factory personnel. A study of Q141 and Q145 in adjoining fields in the Maryborough area from 1992 to 1994 showed ccs in commercial rakes of cane varied by up to 2.1 units in Q 145, and by 1.1 units in Q 141. Higher variation; up to 6.57 units in Q145 and 3.03 units in Q141, was measured for six stalk samples from a 50x50 m intra-field sampling grid. Up to 82% of variation in ccs between Q145 sites was explained by negative effects of gravel between 25 and 50 cm deep in the soil, high leaf nitrogen and calcium to magnesium ratios in leaves, and positive effects of a greater root zone depth. CCS of Q141 was not affected similarly by these variables, but there was less variation in soil and leaf data in the Q 141 section of the study area. Low ccs within Q 145 was attributed to. lower stalk dry matter, as well as lower sucrose % in the dry matter. The dry matter data, and the significance of soil physical parameters, suggest that water stress may have restricted photosynthesis and sugar production in the dry years of study.