Fiber length and strength are generally determined the first 20 days after flowering and micronaire is determined the next 20 days. Variety is a major determinate of fiber length and strength, while the environmental contributions of management and weather can greatly influence micronaire and fiber color. Late planting usually produces fiber of near average length and strength but lower micronaire than early or mid season plantings. Potassium applications on potassium deficient soils usually results in increases of length, strength, and micronaire over untreated check plots. High rates of nitrogen application tend to result in reduced micronaire. Low night temperature during days 20 through 42 post anthesis generally reduce micronaire. Precise effects of weather during a season aren't well known.