Abstract
Molybdenum (Mo) foliar spray may improve the nitrogen acquisition by the plants and increase the crop yield. The effects of Mo foliar spray on nitrogen nutrition, achene yield and yield components of sunflower were investigate in this study. The experiment was carried out on a Rhodic Hapludox in Chavantes, Sao Paulo, Brazil under conventional tillage system. Treatments consisted of five Mo concentrations [0 (control), 26, 52, 78 and 104 g ha–1 of Mo] applied as foliar spray at the growing stage of eight developed leaves – V8 (18 days after plants emergence). Foliar application of Mo rates reduced the nitrate (NO3–) concentration, and increased the concentrations of ammonium (NH4+), total nitrogen (N) and Mo in the leaf tissue of sunflower. Molybdenum foliar spray did not affect the plant height, stem diameter, capitulum diameter and number of achenes per capitulum of sunflower. Application of 58 and 68 g ha–1 of Mo resulted in increased of the thousand achenes mass (40%) and achene yield (27%) of sunflower, respectively, compared to the control. Molybdenum foliar spray improves the nitrogen nutrition and the achenes mass resulting in the increased achene yield of sunflower. Results suggest that Mo deficiency can compromise the nitrogen metabolism of plants, and result in lower achene yield of sunflower. Key words: Helianthus annuus L., molybdoenzymes, nitrate assimilation, plant nutrition.
Highlights
Molybdenum (Mo) is an important micronutrient for plant growth and occurs in several enzymes catalyzing diverse oxidation–reduction reactions in plants (Mengel and Kirkby, 2001)
Application of 58 and 68 g ha–1 of Mo resulted in increased of the thousand achenes mass (40%) and achene yield (27%) of sunflower, respectively, compared to the control
Molybdenum foliar spray improves the nitrogen nutrition and the achenes mass resulting in the increased achene yield of sunflower
Summary
Molybdenum (Mo) is an important micronutrient for plant growth and occurs in several enzymes catalyzing diverse oxidation–reduction reactions in plants (Mengel and Kirkby, 2001). Molybdenum foliar sprays are often more effective than soil applications, for acid soils, and are most effective if applied at early stages of plant development (Valenciano et al, 2011). Biscaro et al (2011) verified that nitrogen fertilization increased common bean grain yield only when combined with Mo leaf supply. Molybdenum foliar spray (40 g ha–1 of Mo) at 25 days after plant emergence greatly enhanced the nitrogenase and nitrate reductase activities, resulting in increase of total N accumulated in the plant shoots of common bean (Phaseolus vulgaris L.) (Vieira et al, 1998). Calonego et al (2010) found that the absence of Mo foliar supply promoted the accumulation of nitrate in the common bean leaves as result of the increased N availability in the soil, indicating the low efficiency of N assimilation of plants in the absence of this micronutrient. This study investigated the effect of molybdenum foliar spray on nitrogen nutrition, achene yield and yield components of sunflower
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