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Protein, Oil, and Energy Yields of Sunflower as Affected by N and P Fertilization¹

Relatively little information exists on the N and P needs of sunflower (Helianthus annuus L.) on infertile soils in non-traditional production areas. The effects of four levels each of N (0 to 180 kg/ha) and P (0 to 60 kg/ha) applied to a thermic Typic Rhodustult were evaluated over three seasons. In all seasons there were highly significant seed yield responses to N and P a plied. The nature of the N x P interactions indicated a greater response to N fertilization where P had been applied than in the absence of P fertilization. Maximum seed yields of up to 2,600 kg/ha were four to 13 fold higher than yields in the absence of applied N and P. Protein level in the seed was increased by N but decreased by P fertilization, the opposite effects being generally observed with respect to the oil. Nitrogen and P fertilization markedly increased the protein and oil yields, the N x P interactions indicating that P fertilization was necessary for maximum response to applied N. The ratio of seed N to fertilizer N decreased with increased N fertilization but increased with increased P applied. The food energy yield and energy production efficiency of sunflower increased markedly with both N and P fertilization.

Key Words: Helianthus annuus L. • Nitrogen • Nitrogen recovery • Phosphorus

² Research agronomist and agronomy technician, respectively.

Received for publication April 4, 1980.