Yield and leaf composition of sunflower in relation to N, P, K, and lime treatments

Sunflower (Helianthus annus L), a drought resistant crop, is cultivated widely throughout the world. Still, few studies on the fertility requirements of the crop have been published, particularly in relation to cultivation on highly weathered soils and in terms of using foliar analysis as a tool in diagnosing nutritional needs. Two 3⁴ (N, P, K, lime) factorial experiments (high and low fertility levels) with trace elements as split plots were conducted on Farningham clay loam, a Typic Haplorthox. No significant yield response to added N or micronutrients was found on either experiment. Liming and P fertilization increased seed yields in the low fertility experiment. Increased K application gave significant yield increases in both experiments. Preliminary foliar diagnostic norms were developed using the Diagnosis and Reccommendation Integrated System (DRIS). The prognostic value of these norms was tested using the low fertility experiment. In 32 of the 37 cases where the DRIS analysis could be checked against actual experimental yield results, application of the nutrient diagnosed as the most yield limiting resulted in a positive yield response. These data suggest that sunflowers can be a successful crop on Oxisols provided fertility is adequate.