Short-Term Effects of Wood Ash-Based Fertilizers on the Chemical Properties of Oxisol After Cowpea Harvest

The response of fertilizer sources containing wood ash to liming is still poorly understood in tropical soils. The objective was to evaluate the effects of wood ash and organomineral fertilizers whether or not combined with liming on the chemical properties of an Oxisol following the harvest of cowpea (Vigna unguiculata (L.) Walp.) cv. BRS Guariba. The field experiment was conducted in randomized blocks with four replicates, using a 5 × 2 factorial design: no fertilizer (NF), mineral fertilizer (MF), wood ash (WA), simple-mixture organomineral fertilizer (SMOF), and pelletized organomineral fertilizer (POF), with (WL) or without liming (NL). Soil samples were collected after harvest. WA and SMOF reduced acidity and increased P, K, Ca, and Mg content without liming, while POF exhibited the highest P, K, and Ca contents when combined with limestone. Under liming conditions, POF reached 93.85 mg kg−1 of P, 286.14 mg kg−1 of K, 2.56 cmolc kg−1 of Ca, and 64.32% base saturation. The results demonstrate that the response of ash-containing sources depends on liming management: WA and SMOF favored soil chemical properties under natural acidity, while POF performed better when combined with limestone.