EFFECT OF SOIL AND CLIMATE CONDITIONS ON SOLUBLE SOLIDS EVOLUTION DURING MATURATION OF KIWIFRUIT

The increase in soluble solids concentration (SSC) during maturation o f kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguso n 'Hayward') in 16 orchards of the eastern coastal plain of Corsica wa s analysed in relation to soil characteristics and climate data for 2 years (1987 and 1988). Even if time was expressed in degree days, a ye ar-to-year difference in SSC evolution with time was observed. A smoot h decrease in SSC in early October 1987 was noticed and may be the res ult of the high rainfall which occurred during that period. Using the 1988 data set, SSC increase was estimated as a function of time (under a quadratic form), total soil sand level, and the inverse of soil cru de silt level, meaning that soil retention capacity probably influence d SSC increase. The derivative with respect to time of this function w as also an acceptable estimate of observed rate of increase in SSC (RI ). Observed RI, as well as calculated daily RI, increased as mean air temperature decreased, as reported in other papers. These equations we re then tested on the 1987 data set and were also good estimates of SS C and RI except during the high rainfall period. However, the relation between RI and mean temperature was not consistent in 1987 since, in late October, increasing RI were observed with increasing temperature. This suggests that increasing SSC during maturation may not only be t he result of starch hydrolysis but more probably the balance between c omplex physiological processes.