Sweet Potato Response to K and P Fertilization¹

Abstract

Limited literature is available to provide recommendations of K source and rate and P rate for sweet potato [Ipomoea batatas (L.) Lam.] production. Many growers, therefore, continue to use the more expensive sulfate (SO4) source of K rather than chloride (Cl) and higher than recommended rates of K and P. Accordingly, on‐farm experiments were conducted during 3 years on North Carolina Paleudults to determine effects of K source and rate and Prate on sweet potato yield, grade, and quality. Potassium sources were KCl and K2S04. Fertilization rates of K varied over the five K experiments and depended on initial soil test levels which ranged from 0.04 to 0.12 cmol K L−1 by Mehlich‐I extractant. In the three P experiments, the various P rates were also dependent upon the initial soil test levels which ranged from 11 to 30 mg P L−1 also by Mehlich‐I extractant. As K source had no effect on yield, grade, or quality, it was concluded that the higher Cl concentrations, up to 22.8 g kg−1, in vegetative tissue with increasing KCl rates had no detrimental effect on sweet potato yield, grade, or quality. Total yield response to K applications was obtained where soil test K levels were ≤ 0.08 cmol L−1, although no. 1 yields increased only where soil test K levels were ≤ 0.05 cmol L−1. Phosphorus applications had no effect on yield, grade, or quality of sweet potato.

Nutrient Management with Cover Crops and Compost Affects Development and Yield in Organically Managed Sweetpotato Systems

“…In 2001, N concentrations exceeded the N sufficiency range defined by NCDA (3.2% to 4.0%) and were ranked ''high'' or in ''excess'' according to NCDA guidelines. In 2002 and2004, N concentrations were within sufficiency ranges for all systems and were similar to those observed for 'Jewel' by Nicholaides et al (1985) and Hammett et al (1984).…”

“…The Mehlich-3 extraction used in analysis can overestimate the amount of soil P that might be available for crop uptake. However, the P content present in all treatments is clearly higher than sweetpotato requirements (Nicholaides et al, 1985). Cover crops in Mean separation within column and year by Fisher's protected LSD (P # 0.05).…”

“…Several studies have been performed in the southeast to determine the influence of nutrient source and/or rate on sweetpotato root yield under conventional management (Hammett et al, 1984;Mascianica et al, 1985;Nicholaides et al, 1985;Phillips et al, 2005;Purcell et al, 1982), but no such data have been collected for organic systems. To assess the adequacy of nutrient supply and to examine the influence of cover crop management on sweetpotato nutrient uptake and productivity, a 3-year field experiment was designed to test three organically managed systems with and without cover crops and tillage compared with a conventionally managed system with tillage and chemical pest controls.…”

Sweet potato yields and nutrient dynamics after short-term fallows in the humid lowlands of Papua New Guinea

“…biomass of which II2 kg ha-I was released within eight weeks (Hartemink & O'Sullivan, 2001). Sweet potato has a high demand for K (George et a!., 2002;Nicholaides et a!., 1985) and K influences tuber yield via increased dry matter allocation to the tubers and an increase in number of tubers per plant (Bourke, 1985a). Sweet potato has generally a low demand for P (Hahn & Hozyo, 1984) and as the soils had fair amounts of available P, the recycling of P by the fallow crop had possibly little effect on sweet potato yield.…”

Broadening the Objectives of Future Potassium Recommendations

“…By comparison, increases in yield and quality of sweet potato (Ipomoea batatas L.) were not influenced by K source. In general, K fertilization increased the frequency of large tuberous roots in this species and slowed weight losses in storage; an index of quality (Nicholaides et al 1985). In a 13 site-year study where the addition of K to N-and P-fertilized soil more than doubled tuber yields, John et al (2013) reported increased tuber yield and a slight increase in tuber starch concentration for cassava (Manihot esculenta Crantz) with K fertilizer application.…”