Comparative effects of potassium humate, feldspar, and chemical potassium fertilizers on the yield of yam (Dioscorea abyssinica) under Egyptian conditions

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Yams (Dioscorea spp.) are a major tropical tuber crops used as staple or secondary food for more than 500 million people worldwide. Large amounts of potassium-related fertilizer are used in agriculture to improve crop yield and soil K content, but the high cost and overuse have caused soil and environmental concerns. Therefore, the aim of this work was to study the use of natural sources of potassium (K-humate and feldspar) as an alternative to chemical potassium fertilizers and to increase the productivity of yam (Dioscorea abyssinica) under Egyptian conditions. Two field experiments were established at Kaha Vegetable Research Farm, Qalyubia Governorate, Egypt, during two successive seasons of 2021/2022 and 2022/2023. The experiment was arranged in a randomized complete block design with three replicates. The plot area was 10m² (10 m in length and 1 m in width). The drip irrigation was used. The experiment consist of eight potassium treatments, control treatment (144 units K₂O) as potassium sulphate (48% K₂O), and three levels of feldspar (100, 80, and 60% of recommended fertilizer) and three levels of potassium humates (100, 80, and 60% of recommended fertilizer) and a mixed treatment (40% potassium humate + 60% feldspare). Our results indicated that using natural sources of potassium, i.e., feldspar and humate, can serve as alternative sources of potassium (potassium sulphate). The treatment 60% K-feldspar + 40% K-humate+KSB increased all the vegetative growth parameters, total yield of yam tubers, quality and chemical composition, while the treatment of 60% K-humate increased total saponin content of tubers in both seasons.