Potato (Solanum tuberosum L.) contributes to global food security due to its high yield in terms of volume and nutrients. It supplements or replaces grain-based meals when transport chain disruptions reduce the availability of grains such as wheat (Triticum aestivum L.), rice (Oryza sativa L.), and maize (Zea mays L.) (Camire et al., 2009). Its adaptability to diverse environmental conditions and high yield potential make potato an ideal vegetable for ensuring food and nutrition security (Kyamanywa and Kashaija, 2011). In terms of volume, potatoes are the fourth most produced crop in the world, after rice, wheat, and maize (Hirpa et al., 2010). It ranks first in production volume among tuber and root crops (Cromme et al., 2010). In addition, potatoes are adaptable to numerous climates and cultures, and their global consumption has increased (Campos and Ortiz, 2019)
Florida is among the top spring potato production states, although yields are far lower than those of the midwestern and western United States (DeFauw et al., 2012). However, increasing potato yield and quality with conventional fertilization techniques is challenging because of the old fertilizer recommendations; as a result, new agronomic strategies are required to meet the producer and industry demands(Sharma et al., 2017).
Nutrients such as nitrogen (N), phosphorous (P), and potassium (K) have been extensively studied and recommended for potatoes in Florida. In addition, crop sulfur (S) requirements become essential because of the decreasing atmospheric S deposition and increasing fertilizer's purity with time (Hinckley et al., 2020; Weil and Brady, 2018). The S is critical for potato tuber quality, N assimilation, amino acid production, and protein synthesis. Nevertheless, different sources of S are available, which have varying characteristics when interacting with soil, environment, and plants. Such as, in the coarse sandy soils of Florida, S leaching is the challenge that makes it more difficult to retain S in soil for later stages of plant growth, mainly if the S sources are applied as sulfate (SO42−) (Grant et al., 2012; Stark et al., 2004).
The impacts of S sources on crop growth yield, diseases, quality, and soil health were explored. Grant et al. (2012) found that adding S as a sulfate boosted rapeseed yield. Furthermore, S application was shown to have an interaction impact when combined with polymer-coated urea in N uptake (Geng et al., 2016). The research on peanuts found that gypsum was the best S source for application, followed by single super phosphate and ammonium sulfate in typical haplaquent soil (Prasad, 2003). The naturally occurring S forms elemental S, and SO42− S may be employed. Three-year research on sandy loam soil using three S sources indicated that only 7% of S leached from the soil in the first year when administered with a mixture of bentonite clay and S followed by micronized elemental S (26%) and ammonium sulfate (AS) (72%). After three years, Riley et al. (2002) observed that 33%, 75%, and 96% of S leached from bentonite clay and S, micronized elemental S, and AS, respectively. Furthermore, Sharma et al. (2023) reported higher tuber yield when treated with magnesium sulfate (EPTOP) or gypsum than AS.
Vegetative indices (VIs) such as normalized difference vegetation index (NDVI), normalized difference red-edge index (NDRE), and chlorophyll content (CC) have historically been used to assess plant health. The VIs monitors the plant cell composition, which fluctuates with changes in plant chemistry, development stage, and environment, by focusing on a particular band of lights reflected by the plant canopy. These VIs may be utilized to research the S source response since S deficiency symptoms appear on the plant's young leaves. Puyska et al. (2018) used SPAD and chlorophyll fluorescence to investigate the impact of foliar S and B application on oil seed rape and reported a significant increase in yield due to the application of S. Pagani and Echeverra (2011) also reported that applying S boosted maize yield, total biomass, S concentration, and the changes were detectable by chlorophyll meter readings.
Extensive research is still required to fully comprehend the S concentration response to light reflection to adapt to advanced technology, such as active and passive sensors. Therefore, this study was conducted to investigate the effect of S sources on the various aspects of potato cultivation with the objectives a) to understand the S source, rate and location effects on in-season soil S movement, potato biomass production, and S uptake by potato plants. It also includes the VIs as in responses of treatments.
The part of the experiment already published(Sharma et al., 2023) which discussed the effects of S sources and rates on the potato tuber yield, specific gravity internal and external tuber quality. In that study it was reported that the EPTOP and gypsum outperformed the AS in tuber yield. Where the maximum yield was reported from the lower rate (45 kg ha− 1) compared to the higher rate (90 kg ha− 1). The S source and rates did not had effects on the internal and external tuber quality. This article discusses the S source and rate responses measured as soil S availability, Crop biomass, VIs, and S uptake.