Response of Egyptian Cotton to Soil and Foliar Potassium Application Under Calcareous Soil Conditions

Abstract

Two field trials were conducted in a highly calcareous sandy clay loam soil at Nubaria Agric. Res. Station, Agric. Res. Center, Alexandria governorate, Egypt during 2012 and 2013 seasons to study the effect of some sources of potassium fertilizer, soil and foliar potassium application treatments on growth, earliness, yield and its components of Egyptian long staple cotton cultivar Giza 86 (Gossypium barbadense, L.). Potassium fertilizer was added according to the experimental treatments (source, rate, method and date of application). Potassium sulphate (48% K2O) was applied at the rate of 24 and 2.4 kg K2O/fed., for the soil and foliar applications, respectively. Potassium humate fertilizer (20% humic acid and 8% K2O) was applied at the rate of 2 and 1 L/fed., for the soil and foliar applications, respectively. Potassein fertilizer (30% K2O and 10% P2O5) was applied at the rate of 2 and 1 L/fed., for the soil and foliar applications, respectively. The soil applications after thinning in the form of potassium source. The experimental design was a split plot with four replications. The main plots involved the three sources of potassium fertilizer namely; A- Potassium sulphates, B- Potassium humate and C- Potassein. The sub main plots involved the five treatments of potassium application namely; 1- Soil application at thinning, 2- Soil application + foliar spraying two times (at initiation of flowering and two weeks after flowering), 3- Soil application + foliar spraying three time (at squaring, initiation of flowering and two weeks after flowering), 4- Foliar spraying two times ( at initiation of flowering and two weeks after flowering) and 5- Foliar spraying three times (at squaring, initiation of flowering and two weeks after flowering). The most important results obtained could be summarized as follows: 1)  The all sources of potassium had significant effects on all growth attributes in 2012 and 2013 seasons. 2)  The potassium humate fertilizer significantly decreased No. of days from sowing to the first flower appearance as well as, to the first opening boll, boll age and consequently, increased earliness percentage. 3)  The treatment of potassium humate produced the highest values for No. of opened bolls/plant, boll weight and seed cotton yield/plant and consequently, the highest seed cotton yield/fed., while, the sources of potassium fertilizer did not exhibit any significant effect on No. of plants/fed., at harvest in both seasons. 4)  The application times had significant effects on all growth attributes. The soil application with foliar application sprayed three times at squaring, start and peak of flowering stages, significantly, decreased days from sowing to the first flower appearance as well as, to the first opening boll and boll age, and increased earliness % compared to the other potassium application treatments, and significantly increased No. of opened bolls/plant, boll weight, seed cotton yield/plant and consequently seed cotton yield/fed. in both seasons.