A field experiment was carried out on a sandy soil at Ismailia Agricultural Research Station, Kassasin, Egypt, cultivated with sweet pepper plants (Capsicum annuum L.) during the growing winter season of 2016 and spring 2017, to study the potential benefit of applied different forms of potassium as organo-K (fulvate and humate) and activator-K (citrate and gluconate) on sweet pepper yield and some fruit quality. The applied treatments of the studied potassium were foliar and soil application, with special reference to the control treatment (an initial nutritional status). The potassium compounds were sprayed with 1 kg/400 liter fed-1 applied among three times, after 35, 50 and 75 days from planting.
The data obtained reveal that sweet pepper yields and their quality showed a superior effect for foliar spray compared to soil application. The potassium humate and citrate recorded the superior increases in both macro- micro nutrient content in sweet pepper fruit and vegetative parts with more availability in soil under investigation. It is evident that the applied potassium humate achieved many of the beneficial effects on soil hydro physical and fertility status as well as plant parameters, since K-humate acted like plant growth hormones and partially capable to retain water and nutrients for growing plants due to containing humic acid, which would act as complexing agent, thus minimizing the loss of nutrients by leaching. These chelating agents, through phenolic and carboxylic active groups for micronutrients and water molecules, are considered as a storehouse with easily or available to be taken by plant roots, and this reflected positively on development of yield and its attributes for studying sweet pepper crop.
From aforementioned results, it can be concluded that the application of potassium either in organo or activator sources specially potassium humate under both foliar spray and soil application increased sweet pepper crop yields and their quality as well as improved the nutritional status of both plants, fruit, with relatively higher ability for increasing availability macro- micronutrients in soil under soil application than foliar one.