Corn ( Zea mays L.) plays an important role in human and animal nutrition, biofuel production, and international economics. It is essential to fulfill the nitrogen (N) requirements to attain high yield potentials, provided that a recommended optimum N rate (ONR) is both economically and environmentally sustainable. The agronomic and economic ONR (AONR and EONR, respectively) and the yield‐goal‐based N rate (YGR) are benchmarks used in N recommendation systems. However, edaphoclimatic conditions, crop physiology, and field crop history might influence ONR estimations. This study aimed to compare AONR, EONR, and YGR in 3 years (2022, 2023, and 2024) and two fields. Response curves were created for different groupings: field‐year (six levels), year (with fields combined, three levels), field (with years combined, two levels), and complete dataset (one level). The AONR, EONR, and YGR were calculated from the best model for each level of grouping and ranged between 229 and 412, 229 and 351, and 219 and 318 kg ha ⁻¹ , respectively. Eight out of 12 levels were best regressed to linear‐plateau curves, while four followed quadratic curves. The EONR was either lower or equal to the AONR. The YGR did not adequately detect field‐year variability, meaning that growers might over‐ or under‐fertilize corn in Florida, applying 32 kg ha ⁻¹ more to 46 kg ha ⁻¹ less N than the EONR. These findings raise the question of which is the best approach to determine an ONR in Florida: regression or arithmetic. Further research needs to be addressed to improve estimation methods and account for field‐ and/or year‐specific variability.

Sandy soils are prone to potassium (K) leaching; therefore, developing guidelines for the optimum K application rate and fertilizer source is necessary. This research aimed to evaluate the optimum K fertilizer rates and identify the best K fertilizer sources for potato ( Solanum tuberosum L.) production, considering the impacts of insufficient or excessive fertilization on potato yield and tuber quality. The experiment was carried out on Florida sandy soil in a randomized complete block design with four replications and nine treatments, a combination of three K sources (potassium sulfate [K ₂ SO ₄ ], potassium chloride [KCl], and potassium magnesium sulfate [K ₂ Mg ₂ (SO ₄ ) ₃ ]) and three rates (224, 280, and 336 kg K ₂ O ha ⁻¹ ). Potato tuber yield was affected by different K fertilizer sources. Applying KCl resulted in a 10.3% and 9.0% increase in marketable and total tuber yield, respectively, compared to K ₂ SO ₄ . However, KCl application resulted in significant tuber quality deterioration regarding lower tuber‐specific gravity. Yield and quality of potatoes were improved with the application of K₂Mg₂(SO₄)₃. No significant increase in tuber yield with increasing K rates from 224 to 336 kg K ₂ O ha ⁻¹ . The highest K rate (336 kg K ₂ O ha ⁻¹ ) resulted in a 10‐fold and threefold drop in tuber‐specific gravity values in 2022 and 2023, respectively, compared to 224 kg K ₂ O ha ⁻¹ . These results suggest that K application rate and fertilizer source must be optimized to balance potato yield and tuber quality.

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.

Nitrogen (N) is essential to maximize corn ( Zea mays L.) yield; however, over‐ and underapplication can cause environmental concerns or yield losses. Optimizing N management is critical to balance productivity and sustainability. This study was conducted during 2022–2024 in Florida to determine corn N response. The experiment included six N rates (0–392 kg N ha ⁻¹ by 78.5 increments) over 3 years, with an additional rate (471 kg N ha ⁻¹ ) in the third year, using a randomized complete block design with four replications. Results showed that 314–471 kg N ha ⁻¹ produced the highest and statistically similar aboveground biomass (21,598–23,166 kg ha ⁻¹ ), grain yield (12,479–13,588 kg ha ⁻¹ ), and N uptake (227–250 kg ha ⁻¹ ). For grain N removal, (144–162 kg ha ⁻¹ ), 392 and 471 kg N ha ⁻¹ were statistically similar, while 314 kg N ha ⁻¹ was significantly lower than 392 kg N ha ⁻¹ , indicating a threshold response beyond 314 kg N ha ⁻¹ . Agronomic N use efficiency and partial factor productivity were highest at 157 (58.8 kg kg ⁻¹ ) and 78.5 (57.9 kg kg ⁻¹ ) kg N ha ⁻¹ , respectively. Results suggest no agronomic advantage above the 314 kg N ha ⁻¹ rate, and yield decreased at 471 kg N ha ⁻¹ . Response analysis indicated that 24.4 g N was required per kg of corn grain under irrigation system. The nitrogen nutrition index confirmed that moderate applications (235–314 kg N ha ⁻¹ ) sustained crop N status, while higher rates (>392 kg N ha ⁻¹ ) offered little to no benefit. Collectively, these results support refining N recommendations to optimize agronomic production in Florida.