Edaphic and physiographic attributes and death of cacao trees in drought years

Abstract

AbstractOccurrence of more frequent events of prolonged periods of low rainfall (drought) in worldwide cacao (Theobroma cacao L.) production zones has not only compromised productivity of small farmers but also crop survival. This study aimed to evaluate how and to what extent cacao tree mortality in dry years is related with variations in soil and physiographic features. The rate of mortality of cacao trees cultivated under an agroforestry system was evaluated over three periods (1994–1995, 2009–2013, and 2015–2019) on 36 plots of a farm in Bahia, Brazil, which has a wide diversity of soils and is established in a region with a subhumid to dry climate. Correlation analyses (single and multiple), cluster analysis, and Tukey tests were performed. The explanatory variables studied were the attributes of two soil layers (physical, mineralogical, and chemical), the diagnostic horizon, and the physiographic attributes (slope, terrain orientation in relation to the sun, and crop shading). The edaphic attributes most related to cacao tree mortality were physical (granulometry, porosity, and density) and mineralogical (Ki), mainly in the subsurface layer. The lowest mortality was observed in Oxisols and on slopes facing south and east. It was possible to establish recommend limits of the most suitable edaphic attributes to ensure greater survival of cacao trees cultivated in regions subject to recurrent water deficit similar to the conditions of this study. These findings can be used to guide farmers on how to mitigate the effect of drought.