Strawberry iron-manganese chlorosis: a mathematic model to understand the phenomenon

For the El Bajío in Guanajuato state, strawberry (F. × ananassa) has been a traditional crop with social and economic importance for more than 130 years. It has been planted mainly in vertisol soils, whose physicochemical characteristics are: clay content greater than 60%, poor in organic matter, pHs higher than 8.2, and irrigation water high in bicarbonates. Since the 1980s, there has been present an abiotic disease, a chlorosis, for which nowadays there are enough evidence to call it “iron-manganese” deficiency. The objective of the present work was to develop a model that describe which variables explain the deficiency and for this, soil samples were taken at 0-30 cm deep from 157 strawberry farms with some degree of chlorosis in El Bajío region and their physicochemical characteristics and macro- and micro-elements were measured. Twenty-six variables were studied by regression analysis, but only the nine that appear in the model contributed to a satisfactory explain the relationship Fe/Mn=GROTERDAN1.5 dimensionless quotient obtained by dividing the concentration in ppm in the soil of both elements. Fe/Mn = -0.0345-0.03913*pH - 0.01424*EC - 0.00060371*Mn + 0.019636*soil moisture + 0.01093* organic matter + 0.007447*loam + 0.006654*sand + 0.004902*clay + 0.0021613*Fe; n=157; R²=0.779***; F_α0.05=0.247*; F_α0.01=0.290**. This equation can be used with data obtained from conventional soil analysis, from which another model, that establishes the link between it and strawberry production (t ha^‑1), was generated.