By Davie Kadyampakeni, Tripti Vashisth and Duplicate Sambani
The University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) conducted an experiment for four and a half years to determine effects of soil amendments on soil pH. The impacts of fulvic acid, humic acid and sulfuric acid with and without elemental sulfur were compared. Canopy size, fruit yield, fruit quality, soil nutrient availability, leaf nutrient levels and root density were tracked and analyzed in the field.
Moderate acidity (5.5–6.5) promoted nutrient availability compared to pH greater than 7.5. There was positive correlation between soil pH and soil calcium (Ca), magnesium (Mg), zinc (Zn), manganese (Mn) and boron (B), possibly suggesting that the availability of these soil nutrients increased as pH increased (see Figure 1 and Figure 2).
A negative correlation was observed between soil pH and soil iron (Fe), sulfur (S), potassium (K) and phosphorus (P), indicating decreased nutrients in soil solution as pH increased (see Figure 1 and Figure 2). Fulvic acid + elemental sulfur increased root density, while humic acid + elemental S showed a significantly lower root density.
Use of organic acids such as humic acid and fulvic acid should be considered for lowering soil pH along with elemental sulfur. Combined use of organic acids and elemental sulfur increased nutrient availability on Florida sandy soils. However, fruit yields and fruit quality were comparable between treatments over the four years.
Davie Kadyampakeni and Tripti Vashisth are associate professors, and Duplicate Sambani is a graduate research assistant — all at the UF/IFAS Citrus Research and Education Center in Lake Alfred.
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