Biostimulant application of whey protein hydrolysates and potassium fertilization enhances the productivity and tuber quality of sweet potato

Utilizing biostimulants like protein hydrolysates is one of the most creative and promising approaches to improving nutritional efficiency, abiotic stress tolerance, or crop quality traits. In the present study, whey protein was hydrolysed with trypsin for 4 h at an enzyme/substrate ratio (1/300, w/w). The obtained whey protein hydrolysates (WPH) were chemically characterized, and their antioxidant activity was estimated. WPH, which was produced using trypsin for 4 hours and presented the highest antioxidant activity. Therefore, it was selected as a bio stimulant with potassium fertilization for enhancing the productivity and tuber quality of sweet potatoes. A field experiment was carried out during the two successive summer seasons, at a private vegetable farm in Faques City, Sharkia Governorate, Egypt, to study the effect of different potassium rates (50, 75, and 100 kg K2O/fad) and WPH at 0.10 and 0.20% as a foliar application compared to unsprayed plants (control). The interaction between K2O at 100 kg /fad and spraying with WPH at 0.15% increased shoot dry weight/ plant, N, P, and K uptake by shoots, yield/plant, marketable yield, and total yield/fad, as well as average tuber root weight. It was concluded that the most efficient bio-stimulating foliar spray treatment for increasing sweet potato productivity was WPH (0.20%).