Ramifications of variations in quality of pasture seed lots marketed in Uasin Gishu, Kenya

The low levels of germination, varied vigour and long periods required to attain required stand establishment in pasture fields compromises the expected quality standards of marketed seed. This study was carried out to explore the effects of laboratory determined seed quality on the germination, vigour and stand establishment of seed lots of Rhodes grass. Certified seed lots of Rhodes Grass (Chloris gayana cv Boma) were obtained from registered seed stockists in April 2006, and compared for bulk quality determined by assessment of purity, standard germination and vigour in laboratory and in green house and field experiments. Four (4) different seed lots of Rhodes grass were used as treatments and sown in three (3) replications laid out in randomized Complete Blocks. Daily growth rates of heterotrophic seedlings in the laboratory were recorded and emergence and final count was assessed in the greenhouse and field. Data was subjected to analysis of variance (ANOVA) and means were separated using the least significant difference (LSD). Laboratory germination ranged from 42.00% to 47.75% while field emergence ranged from 13.00% to 21.50%. Field stand establishment for the four seed lots averaged 17.38%. The pure germinating seed (PGS) range of the seed lots was between 18.94 to 27.38%, while mean germination time (MGT) ranged from 2.94 to 4.56 days. Out of all seed quality attributes, caryopsis count (PCC) and MGT, as attributes of purity had the highest correlation with field emergence. The results support the incorporation of caryopsis count on pure seed fractions as an additional check to improve the evaluation of Rhodes grass seed purity. Vigour tests give more accurate assessments on germination uniformity and of the planting quality of pasture seed.