Effect of Potassium Management on Lint Yield and Fibre Quality of Cotton in North China

During 2012 and 2013, 60 cotton fields were randomly selected to investigate the relationship between soil K supply and cotton yield/fibre quality in Hebei, Henan, Shandong, and Xinjiang Provinces. The effects of application rate and time of K fertilization on cotton yield and fiber quality were also studied in each province. Exchangeable K values in the soil of Shandong (mean=232 mg/kg) and Xinjiang (217 mg/kg) cotton fields were higher than that in Henan (128 mg/kg) and Hebei (133 mg/kg) cotton fields. In Henan, Shandong and Xinjiang, soil exchangeable K, total plant K uptake, seed cotton or lint uptake K were significantly and positively correlated with seed cotton and lint yield. The relationships between soil exchangeable K and fiber quality indices (length of fiber, fiber length uniformity, linter index, fiber strength, fiber elongation, macronaire value, fiber maturity ratio) were variable, but significantly and positively correlated with macronaire value.

Application of fertilizer K increased lint yield by 1 to 9% (Hebei), 14 to 68% (Henan), 5 to 14% (Shangdong), and 8.5 to 27% (Xinjiang). The agronomic efficiency of K was <1.2 kg lint/kg K₂O, 0.7 to 2.0 kg lint/kg K₂O, 0.7 to 2.1 kg lint/kg K₂O, and 2.7 to 9.8 kg lint/kg K₂O for the four provinces, respectively. Also, the economic benefit from K application was US$220 to 540, $420 to 2,130, $285 to 680, and $608 to 1,885/ha for the four provinces, respectively. Application of K increased length of fiber, fiber length uniformity and fiber strength. Application of K also decreased macronaire values, but did not affect fiber elongation in Hebei. Length of fiber, fiber strength and fiber elongation increased with K application in Henan, while fertilizer K application did not significantly affect various fiber quality indices in Shandong and Xinjiang. The appropriate application rates of K fertilizer in cotton at Hebei, Henan, Shandong, and Xinjiang were 150, 240, 180, and 150 kg K₂O/ha, respectively. The right time of K application in Hebei, Henan and Xinjiang was determined as 50% K at bud stage plus 50% K at boll stage, while in Shandong, 50% K is applied as basal preparation and the remaining 50% K at flowering.