Cottonseed Vigor Related to Harvest and Ginning Date 1

We previously reported large variation in field emergence of commercially processed cottonseed ( Gossypium barbadense L.) produced within a small geographical area of Arizona. The current investigation was conducted to determine if there were important management practices associated with the variation in seed vigor. An examination of the seed in question showed that much of the variation was associated with date of ginning and harvesting. Seed ginned after November were generally of low quality for planting purposes. To determine if low quality of late‐ginned seed cotton was associated with field weathering and/or the contribution of low quality seed in late matured bolls, open bolls of ‘Pima S‐5’ ( G. barbadense ) and ‘Deltapine 61’ ( G. hirsutum L.) were harvested periodically during two autumns. The bolls were either exposed to various lengths of field weathering or had matured at different times during the harvest period. The seed was evaluated the following spring for germination, field emergence, and plant growth. Date of maturity had a greater effect on seed vigor than field weathering although both generally caused significant effects. Seed germination and emergence were influenced to a greater extent than plant height taken in the early summer or the date of initial flowering. Although the effect of date of maturity was greater than that of field weathering, the latter would be expected to affect a greater quantity of seed. This study stresses the importance of timely harvesting in order to obtain high quality planting seed.