Black bean (<i>Phaseolus vulgaris</i> L.) response to potassium fertilization in two different soils in Haiti

In the absence of calibrated soil test and proper nutrient recommendations for crop growth, Haitian farmers suffer from suppressed and uneconomical yields. Thus, decisions made by farmers are mostly ineffective not only economically but also resulted on negative impacts on the soils. This mismanagement is also observed in the low level of crop yield in Haiti, especially black bean, where it recorded the lowest yield among the Caribbean nation in 2016, 660 kg ha−1. Other than the inappropriate nutrient management, smallholders also face a lack of resources (technical, human, and financial inputs) needed to increase crop production. Furthermore, soils in tropical and subtropical regions are known to be deficient in exchangeable potassium (K) due to fixation on clay and poor water management. Supplying sufficient K is vital for crop growth and quality characteristics and K deficiency typically becomes a limiting factor in crop production. To understand how black beans respond to K fertilization, a pot study was conducted with two different soils (Kenscoff, acidic and Cabaret, alkaline) in Haiti using a completely randomized block design, replicated four times with four K (0, 20, 40, and 60 kg K ha−1) rates. All treatments received 55 kg ha−1 of phosphorus (P). As a result, black beans in the alkaline soil recorded highest yield of 3053 kg ha−1, when no K was applied, Additional amount of K, when the soil already tested high, in fact, reduced K uptake by the plants. However, the acidic soil recorded optimum yield at 20 kg K ha−1.