EFFECT OF VINE CUTTINGS AGE AND SOME POTASSIUM FERTILIZER SOURCES ON GROWTH AND YIELD COMPONENTS OF SWEET POTATO

Two field experiments were carried out during the growth seasons of 2017 and 2018 at the Experimental Farms of Mallawy Agriculture Research Station, Hort. Res. Institute, Giza, Egypt to evaluate the effect of vine cutting ages and potassium fertilizer sources on the growth of the sweet potato cv "Mabrouka". The treatments comprised three apical vine cuttings ages (3, 5 and 7-days) as well as fresh cutting (control treatment) and four sources of potassium fertilizer (K-sulphate, K-silicate, K-citrate and K-humate). The obtained data revealed that: the highest survival rate of vine cuttings was achieved with the 3-days age and fresh cutting planting. The greatest sweet potato studied parameters [vine fresh weight (ton.fed^-1), storage root yield (ton.fed^-1), biomass yield (ton.fed^-1) storage roots length, cm), and K %] were produced with the treatment of immediate planting and 3-days old cuttings. Also, 5-days old cuttings showed the highest total number of storage roots. Contrariwise, storage root diameter, (cm) storage root dry matter (%) and marketable yield (%) were not affected by vine cuttings age in both seasons.
All potassium sources which were used as foliar application affected the growth and yield parameters of sweet potato cv. "Mabrouka”. The treatments of K- silicate and K-sulphate gave the best results of biomass yield (storage roots + forage weight, ton.fed^-1), marketable yield%, and root diameter. The combined treatments of fresh cuttings and K-silicate foliar fertilizer showed the greatest values for number of storage roots, root yield, root diameter and biomass yield (ton.fed^-1). Also, the 3-days- vine cuttings and K-humate treatment recorded the best results for vine fresh weight (ton.fed^-1).