Peanut responds to K fertilization but not to K timing on low-K sandy soils

Potassium (K) is necessary for plant growth, and insufficient K reduces peanut [Arachis hypogaea (L.)] yield and grade. Peanut production in Florida is on sandy soils with low cation exchange capacity. Minimizing K loss to leaching may be affected by the timing of fertilizer-K application. We evaluated the impact of K fertilization on pod yield and grade of peanut in sites with different soil test K (STK) levels. Treatments comprised a two-way factorial with five fertilizer rates (0, 46, 93, 140, and 186 kg ha⁻¹ K) and four application timings (planting; planting plus early bloom; planting, early bloom, plus 60 days; early bloom plus 60 days). The study occurred at sites Hilltop, Citra, and Sesame with Mehlich-3 STK levels 2, 26, and 40 mg kg⁻¹, respectively, at the University of Florida Plant Sciences Research and Education Unit in Citra, FL. In the low-STK sites (Hilltop, Citra), the relative yield increased quadratically until fertilizer rates reached 160 and 82 kg ha⁻¹ K, respectively, after which there was no further increase in peanut pod yield. At Sesame, pod yield was not affected by K rate. Splitting K applications did not improve pod yield at any site in these seasons, which had few leaching rains. Proportion of sound mature kernels (TSMK) was affected only by site, averaging ≥75%. Fertilizing peanuts with 82–160 kg ha⁻¹ K maximized pod yield in soils with Mehlich-3 STK ≤26 mg kg⁻¹, and different responses to K fertilizer rate observed at fields with different STK levels within the low STK index category suggests justification for splitting this category. A single K application is sufficient in sites with low incidence of leaching rains.