Sulfur source effects on soil, vegetation indices, biomass, and uptake in potato

Sulfur (S) is necessary for amino acid production, disease resistance, protein synthesis, and nitrogen assimilation in plants. We tested the performance of three S sources (magnesium sulfate [EPTOP], gypsum, and ammonium sulfate [AS]) at two different rates (45 and 90 kg S ha⁻¹) on soil S availability, vegetative indices (VIs), above- and belowground biomass (BGB), and potato (Solanum tuberosum L.) S uptake. For VIs such as normalized difference vegetative index, normalized difference red-edge index, and chlorophyll content, the maximum values were reported when gypsum and EPTOP were applied compared to AS. These differences were decreased later in the season. Significant interaction effects were reported among sites, sampling events, and sites and S sources for aboveground biomass (AGB). Similar trends were reported for the BGB, where the significant interaction effect was reported among the S sources and sampling event and S sources and sites. The AGB S uptake was affected due to the sites and sampling event. However, BGB S uptake was influenced by the interactive effect of S sources, sites, and sampling events. The VIs did not have a significant association between soil S concentration and AGB S uptake. It was found that the field history had a notable effect on the crop responses to variable S sources. In conclusion, applying S rates and sources has distinct responses, which depend on soil history and chemical properties, and that should be considered when making choices for S application in potatoes.