Potassium Use Efficiency of Safflower and Sunflower Grown in Different Soils
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Using alternative crops that use supplied nutrients efficiently is a possible approach in land use sustainability. Plant species vary in their potassium (K) use efficiency in soils of low K availability by using different strategies. Growing K efficient species to improve yield may be desirable if K efficiency mechanisms are illustrated. Therefore K use efficiency of the alternative oil crops safflower and sunflower was investigated under semi-controlled conditions in sandy and loamy soils using four K supplies. Both species reacted strongly to increasing K supplies in both soils and performed better in loamy soil, although they contained less K concentration in loamy soil. Under suboptimal K supply in both soils, safflower was superior over sunflower by having higher agronomic efficiency (greater relative yield), higher internal K concentration, better relative K accumulation in dry matter. Both species had similar K efficiency ratio (KER) in sandy soil, but sunflower was more efficient in loamy soil. Sunflower was superior over safflower in terms of utilization index (UI) in both soils. Sunflower had less external K requirement and recovered more K than safflower in both soil types. The K use efficiency of crops is based on different competitive components. Thus using different measures of utilization efficiency parameters to differentiate plant species and genotypes to superior and inferior could be in some cases misleading. Neither safflower nor sunflower showed a combination of high values of all K uptake and utilization efficiency components in both soils at studied K levels.