Split applications of molybdenum fertilizer on common bean increase molybdenum in seed

Abstract

Common bean (Phaseolus vulgaris L.) plants sprayed with molybdenum (Mo) fertilizer produce Mo‐enriched seeds, which may increase yield in Mo‐poor soils. The challenge has been to produce Mo‐enriched seeds with less fertilizer. Split applications of Mo increase seed Mo content (SMoC), but the number of splits that maximize SMoC has not been studied sufficiently. In three sprinkler‐irrigated field trials, we evaluated the effects of split‐applied Mo fertilizer on SMoC and seed physiological quality. All treatments received NPK fertilizer at sowing. In two treatments, 69 kg ha−1 of urea‐N was top‐dressed or not applied. In six treatments, Na2MoO4·2H2O was foliar‐sprayed once at either 90 or 600 g ha−1 of Mo at the 4th trifoliolate leaf (V4) growth stage, or 600 g ha−1 was split equally at V4 and bud initiation (R5); V4, R5, and full flowering (R6); V4, R5, R6, and early pod formation (R7); or V4, R5, R6, and early and late R7 growth stages. Seed yield for each trial ranged from 3723 to 4621 kg ha−1. Site‐treatment interaction was significant for SMoC and seed germination (p < 0.001). SMoC ranged from 0.11 to 0.23 (only NPK‐fertilized), 1.81 to 3.31 (600 g ha−1, no split), and 5.22 to 6.29 μg (four splits). Four and five splits did not differ significantly for any variable. In two trials, seeds from 600 g ha−1 of Mo had a 3.9% higher germination than seeds from 90 g ha−1. In conclusion, SMoC increases as the number of splits increase up to four times. Additionally, Mo applied at 600 g ha−1 may improve seed germination rate.