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Sunflower Nutrient Uptake, Growth, and Yield as Affected by Nitrogen or Manure, and Plant Population¹

Sunflower (Helianthus annuus L.) is a new crop in the Southern High Plains. It was grown on Pullman clay loam (Torrertic Paleustoll) in an experiment designed to determine the effects of N, plant population, and row spacing on growth, yield, and nutrient uptake. Fertility treatments were 0, 84, and 168 kg N/ha and residue from three annual applications of 22 and 67 metric tons of manure/ha (wet wt.). Populations of 37, 62, and 99 thousand plants/ha were grown in a bed-furrow irrigation system in two row spacings (one and two rows 30 cm apart) per bed. Beds were spaced 1 m apart. The crop was irrigated to provide adequate water. Beginning about 7 weeks after planting, samples were taken at 2-week intervals for dry matter yields and chemical analyses. Seed and oil yields were taken at maturity.

In 1975, the seed yield on the unfertilized treatment was 1,950 kg/ha, whereas all other treatments produced similar yields averaging 2,850 kg/ha. In 1976, yields were similar on the unfertilized and inorganic N treatments (avg. 2,000 kg/ha) and similar on the manure treatments (avg. 2,330 kg/ha). Lower sunflower yield in 1976 than in 1975 is attributed to higher temperatures during the seed filling period in 1976. Both N fertilizer and manure reduced oil percentage in seed. Even though statistically significant effects were found in 1975, yields were not affected to a large degree by differential row spacings and plant population treatments. Dry matter and nutrient yield curves showed that adequately fertilized sunflower produced about 10 metric tons of dry matter/ha containing 200 kg N, 35 kg P, 450 kg K, 180 kg Ca, and 45 kg Mg/ha.

The 84 kg N/ha rate supplied sufficient N for maximum sunflower yields. Apparently, manure supplied some needed element or condition not supplied by inorganic N. That factor was not identified. Plant populations from 37 to 99 thousand/ha gave satisfactory yields.

Key Words: Oil yield • Irrigation • Manure

² Soil scientist and laboratory director, USDA-ARS, USDA Conservation and Production Research Laboratory, Bushland, TX 79012.

Received for publication January 12, 1982.