Effect Of Potassium Application Methods On Growth And Yield, Fiber Quality Of Different Cotton Varieties

The study was conducted using three different materials (L21, L22and L28) inAgronomic Experiment Station of Shandong Agricultural University. Two methods ofapplication of potassium fertilizer, namely Potassium rates of100kg K2O applied as basaldressing and Potassium rates as1/2basal dressing and1/2top-dressing, were adoptedrespectively. Field management followed essentially the normal agricultural practice. Themain results were listed as follows：1. Effect of potassium application methods on growth and development of differentcultivated varietiesThe results show that both two application methods of potassium fertilizer increasedplant height finally and had no effect on first fruit branch height and fruit branch number.Basal application of potassium fertilizer increased plant height and leaf area per plant of allthree cotton species, enhanced the total leaf number of L21at seedling stage. Split applicationof K2O100kg/hm2had less effect than basal application; but it increased the total nodenumber of L22and L28significantly. Among all species, L21at seedling stage and L22, L28at final stage were most impressible to potassium application.2. Effect of potassium application methods on leaf physiological characteristics ofdifferent cultivated varietiesCompared with the contrast, application of potassium could increase chlorophyII content,Fv/Fm, Fv/Fo, ETR, ΦPII value, EVAP and photochemical efficiency of different cottonvarieties, decrease soluble sugar content of leaves. Different methods of application ofpotassium had different effect on three species at seedling and final stages. Basal applicationhad better influence on photosynthetic capacity of L22at seedling stage and L21at bud stagethan L28; split application had greater effect on photosynthetic capacity of L21at final stagethan L22and L28.Compared with the contrast, one-time basal application of potassium fertilizersignificantly increased the leaf CAT activity of three varieties and SOD activity of L22,decreased the POD activity and MDA content of L21. Split application of potassiumincreased CAT activity of L21, SOD and CAT activity of L22, SOD activity of L28;decreased POD activity and MDA content of L28.Compared two methods, split application increased SOD and CAT activity of L21, CAT activity of L22, SOD activity of L28, reducedMDA content of all three cultivars. Among three different varieties, split application ofpotassium contributed the most on improving senility index of L21at final stage.Compared with the contrast, potassium application could improve the content of nitrogen,phosphorus and potassium in leaves of different cotton varieties, and the effect on nitrogenand potassium was greater than the effect of phosphate. Both two methods of potassiumapplication had bigger effect on nitrogen, phosphorus and potassium content of L21than thatof L22and L28at all growth period. Compared with basal application, nitrogen, phosphorusand potassium content of L21had a significant enhance under split application condition.3. Effect of potassium application methods on fiber quality of different cultivatedvarieties at different fruit positionApplication of potassium was effective to improve the fiber quality of cotton, butdifferent application methods of potassium performance varied in different cotton species.Under basal application condition, fiber length of L21and L28, fiber strength and micronairevalue of L22increased. Under split application condition, fiber length, micronaire value,maturity and uniformity of L21, fiber strength, maturity of L22, fiber length, micronaire valueand uniformity of L28increased. Compared with basal application of potassium fertilizer,fiber length of L21increased significantly under split application condition. Among threecultivars, fiber quality of L21exhibited a higher sensitivity.4. Effect of potassium application methods on yield and yield compinents of differentcultivated varietiesCompared with the contrast, application of potassium increased seed-cotton yield andlint yield of L21, L28and seed-cotton yield of L22. Especially, split application significantlyincreased seed-cotton yield and lint yield of L28. Among all species,split applicationincreased boll size of L21and L22, boll number of L28.