https://doi.org/10.37229/fsa.fja.2026.02.26

The purpose of this work is to evaluate the impact of potassium solubilizing bacteria (KSB) as biofertilizer combined with varying levels of potassium sulphate (K₂SO₄) soil fertilization, on the growth, yield, chemical composition and storability of sweet potato plants (Ipomoea batatasL.), cv. Minufia 6. It also aims to confirm the potentiality of KSB to partially replace mineral fertilizers without affecting the end product quality and examining the effects of KSB on nutrients (NPK) availability in the soil.  Trials were conducted during the summers of 2023 and 2024 under clay soil conditions. The experiment carried out in a randomized complete block design with 3 replicates of 6 treatments namely and two 100% K₂SO₄ and KSB as controls treatments and four treatments of K₂SO₄ at rates 100%, 75%, 50%, and 25% K₂SO₄ of the recommended dose each combined with KSB. Plant length, number of branches per plant, plant fresh and dry weight, total chlorophyll content, carotenoids content, tuber root length, tuber root diameter, and number of tuber roots per plant were noticeably higher forth treatments (100% K₂SO₄), (100% K₂SO₄+KSB), (75% K₂SO₄+KSB), and to a lesser extent (50% K₂SO₄+KSB). In addition, the highest average fresh tuber root weight, fresh tuber roots weight per plant, total yield, and marketable yield, together with the lowest non-marketable yield, were achieved under the treatments (100% K₂SO₄), (100% K₂SO₄+KSB), and (75% K₂SO₄+KSB). Also, the best results of total carbohydrate, NPK, and protein contents in sweet potato tuber roots were recorded by applying KSB with 100% or 75% of the recommended K₂SO₄ dose. While, throughout the different storage periods the treatment consisting of 50% K₂SO₄ combined with KSB exhibited the lowest percentage of tuber roots weight loss. Soils treated with KSB exhibited an increase in available N with rate of (6-11%), and available P (17-23%) higher than untreated soil after the first and second growing seasons. Furthermore, soils receiving 100% K₂SO₄ combined with KSB showed a significant increase in available K, with levels of 26-37% higher than those treated only with 100% K₂SO₄, across the two growing seasons. The results clearly demonstrated that KSB based biofertilizers can successfully achieve partial substitution of mineral K inputs, allowing a reduction of 25% in chemical K₂SO₄ fertilization without compromising tuber roots yield or quality, while simultaneously contributing to long term soil health. The application of KSB in combination with 75% of the recommended K₂SO₄ dose is recommended as the optimal and most sustainable practice