Estimate of ratooning ability in sugarcane (saccharum officinarum L) under conditions of low-available soil moisture in a savanna ecology of Nigeria.

Ratooning ability (RA) is an important criterion in determining varietal suitability for commercial sugarcane cultivation because of the necessity to spread the costs of planting operations over subsequent ratoon crops. Two estimates of RA were computed with the objective to identify a more suitable approach for estimating the RA of a cultivar under low soil moisture regime by using data collected over four cropping cycles from 48 local and exotic sugarcane germplasm collections. The first estimate was computed using the formula: Rai = 100Sri/PC where RA of a trait i is defined as the ratio of the second ratoon crop (SRC) yield of trait i to the plant cane (PC) yield of trait i expressed as a percentage while the second approach is a generalized formula: Rpi = 100[1-(X2-Xi)/Xa] where Rpi = annualized yield of cane, Xa = the reference yield = [yield of plant cane + yield of first ratoon]/2 and Xi = the individual ratoon yield. Genetic variance (δ2g) estimates for RA were comparable for both methods except for brix and kg-brix. Broadsense heritability estimates (H2B) of RA for cane yield was 0.76 in Method I while it was 0.64 in Method II. Brix had estimates of 0.82 and 0.64 for Methods I and II respectively. Genotypes with poor RA were characterized mostly by sharp decline in cane yield especially between the plant cane and first ratoon crop while those with good RA had the greatest yield decline between the first and second ratoon crops. The similarity in estimates of RA with the two methods or in the genotypes selected on the basis of cane yield, brix and Kg-brix suggests that either of the two methods is equally suitable in estimating RA either under ideal growing conditions or in a moisture stress environment. Keywords: Ratooning ability; Plant cane; Ratoon crop; Rank Summation IndexMoor Journal of Agricultural Research Vol. 6 (1&2) 2005 pp. 16-23