Determination of the most limiting mineral nutrient element for growth and development of sunflower (Helianthus annuus) in southwestern Nigeria

Identifying the most limiting nutrient element among the major nutrient elements (NPK) and its associated deficiency symptoms will go a long way in improving sunflower. Experiments were therefore conducted to identify the most limiting nutrient element and its required rate for optimum production of sunflower. Green house trial using acid washed white sand as growth medium was conducted. There are five treatments (complete nutrient solution, minus N, minus P, minus K, and distilled water) replicated three times, given fifteen treatment units. Fifteen pre-sprouted seeds of sunflower were planted and thinned to 12 plants per pot after one week. K was identified as the most limiting nutrient element. Four levels of K (0, 50, 100, 150 kg K2O/ha) identified in the green house were tried on the field to determine which is the optimum level required for optimum performance of sunflower. Data on agronomic parameters were collected and analysed. The influence of treatments applied has manifested at 2 weeks after planting (WAP) on agronomic parameters taken. The least biomass production and eventual death of sunflower seedlings recorded from plants treated with minus K nutrient solution at 4 WAP pointed to K as the most limiting among the three major nutrient elements (NPK). Highest shoot (198.75 g /plant) and root (42.5 g/plant) yields were produced by minus P and complete nutrient solutions treated plants respectively. The order of limiting is K>N>P. With respect to all agronomic parameters taken on the field, application of K at 100 kg K2O/ha produced significantly higher effects. Highest oil yield (1551.04 L/ha) was also obtained at this level of application but oil content was not influenced by levels of K applied. K was identified as the most limiting nutrient element in sunflower production; it should be applied at 100 kg K2O/ha to produce optimum yield.