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Irradiance and Nitrogen to Potassium Ratio Influences Sweetpotato Yield in Nutrient Film Technique

Dep. of Agricultural Sciences, School of Agriculture and Home Economics

C. E. Morris

Dep. of Vocational Education, School of Education, Tuskegee Univ., AL 36088

^* Corresponding author.

Sweet potato [Ipomoea batatas (L.) Lam] is being grown with the nutrient film technique as part of the National Aeronautics and Space Administration's Controlled Ecological Life Support System (CELSS) program for long-termed manned space missions. Our objective was to evaluated the effects of two levels of photosynthetic photon flux (480 and 960 µmols m^–2s^–1 PPF) and three N/K ratios (1:1.1, 1:2.4, and 1:3.6) on yield of sweetpotato when grown using this technique. Vine cuttings (15-cm length) of ‘Georgia Jet’ and T1-155 were grown in each treatment for 90 or 120d , respectively, in controlled-environment growth chambers. Storage root growth for Georgia Jet and T1-155 increased with light intensity, while foliage growth decreased with high K levels. The number of storage roots produced by each plant increased with intensity only for Georgia Jet but was not significantly influenced by higher K levels for either cultivar. Light by N/K interactions were not significant. The level of PPF exerted a greater effect in enhancing sweetpotato storage root yield in nutrient film than did N/K ratio.

Received for publication May 22, 1992.