TITLE:
Cotton and Soil Responses to Annual Potassium Fertilization Rate
AUTHORS:
Morteza Mozaffari
KEYWORDS:
Cotton, Potassium, Mehlich-3, Soil Test
JOURNAL NAME:
Agricultural Sciences,
Vol.9 No.6,
June
29,
2018
ABSTRACT: The objective of this study was to evaluate the effect of potassium (K) fertilization rate (0, 27.9, 56.4, 84.7, 112.9, and 141.1 kg K/ha) and cotton (Gossypium hirsutumn L.) cultivars of slightly differing maturity on seedcotton yield and Mehlich-3 soil-test K concentrations. The cotton cultivars “Stoneville 4892” and “Stoneville 5599” represented long-season cultivars while “Paymaster 1218” and “Deltapine 444” represented early-season cultivars. The same K fertilizer treatments were applied to the same plots during the three years of the study. Higher order interactions of cropping year, cotton cultivar and K-fertilization rates were not significant (P ≥ 0.50), indicating the two cultivars of slightly different maturity respond similarly to K-fertilization. Cropping year and K-fertilizer application rates significantly affected seedcotton yield (P P ≤ 0.0074), as well as 3-year average, and total seedcotton yields (P ≤ 0.0006). Seedcotton yields ranged from 3418 to 4127 kg·ha-1 and 2980 to 3487 kg·ha-1 in the second and third year respectively while 3-year average and total seedcotton yields were 2943 to 3443 and 8832 to 10,330 kg·ha-1. The relation between annual, 3-year average, and total K application rates and seedcotton yield was linear (R2 ≥ 0.82, P ≤ 0.0125). Potassium fertilization significantly increased post-harvest (fall) Mehlich-3 extractable soil K in all three years (P ≤ 0.0002). This study indicated that, in a representative Mississippi River Delta silt loam soil, when Mehlich-3 extractable K was -1, K fertilization was needed to increase seedcotton yield and prevent soil K depletion. This supports the current University of Arkansas fertilizer recommendations for irrigated cotton production, where application of 56 kg of K ha-1 is recommended to optimize seedcotton yield and prevent soil K reserve depletion when Mehlich-3 extractable soil test K is medium (91 - 130 mg/kg).