ABSTRACT

Profitable cotton growers strive to control fiber quality while maximizing crop yield. The objective of this research was to determine if changes in leaf nitrogen (N) and potassium (K) under nutrient stress are related to yield and quality of different fruiting zones in cotton. Plants were grown outdoors in 1999 and 2000 in large pots using half-strength Hoagland's (control) solution via drip irrigation system until some three-row plots received restricted N or K supply. Lint yield was determined from mature bolls that were ginned individually using a roller gin. Lint from only fruiting branches was grouped according to week of anthesis across a 35-d flowering period, giving five lint groups, from which fiber properties were measured. Yields decreased in plants supplied either 20% of control N at first square onward or 0% of control N from first flower onward. Fiber length and strength tended to be lower in these treatments, and lint group four in 1999 produced short, weak, low micronaire fibers. The year by N treatment interaction was significant for strength. As expected, K stress led to low micronaire. Values less than 3.7 were observed in lint groups three and five in 1999 when K was withheld from first flower onward, and in lint groups two and four in 2000 when K was withheld at first square onward. The year by K treatment interaction was significant for yield, due to larger stress-induced decrease in boll number and dry weight in 2000 than 1999. Results support evidence of strong environmental effects on cotton fiber development, and the negative impacts of K stress on both yield and quality.