The co-application of nitrogen and phosphorus improved nutrient uptake and productivity of Ipomoea batatas plants grown in saline-calcareous soils

A combination of abiotic stresses, such as salinity and calcification, can be even more destructive to crop performance than the effects of each type of stress alone. Two field experiments (in 2022 and 2023) attempted to explore the individual impact of three nitrogenous fertilizer types (NFTs, including ammonium nitrate, urea, and ammonium sulfate: N₁, N₂, and N₃, respectively) and three other phosphate fertilizer types (PFTs, including calcium super-phosphate, mono-ammonium phosphate, and urea phosphate: P₁, P₂, and P₃, respectively) and their interactive effects on nutritional status, physiological growth attributes, yield, and the quality attributes of sweet potato (Beauregard cv.) plants cultivated in saline-calcareous soil. This study was carried out using a split-plot system in a randomized complete block design with three replications. The results obtained for both seasons indicated that ammonium sulfate was the superior fertilizer in terms of its effects on leaf macronutrient contents, except for those of nitrogen and magnesium, which were the most impacted when ammonium nitrate and urea were used, respectively. In addition, plants fertilized with N₁ demonstrated the highest ion homeostasis values, plant height, and calcium and magnesium contents in tuberous roots. Likewise, applying P₃ was the most impactful on leaf macro- and micronutrient content, except for that of calcium, as well as magnesium and copper, which were the most affected when P₁ and P₂ were used, respectively. The use of P₃ also produced the best results in terms of SPAD readings, leaf area, tuberous root volume, diameter, and total root yield. Furthermore, after applying P₁, we recorded the highest ion homeostasis values, tuberous potassium, and calcium content. The coupled application of N₁ and N₃ with both P₂ and P₃ was the most effective in most of the characteristics we studied.