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Grain yield, efficiency and the allocation of foliar N applied to soybean canopies

2019; UNIVERSIDADE DE SÃO PAULO; Volume: 76; Issue: 4 Linguagem: Inglês

10.1590/1678-992x-2017-0395

1678-992X

Silas Maciel de Oliveira, Clovis Pierozan, Bruno Cocco Lago, Rodrigo Estevam Munhoz de Almeida, Paulo César Ocheuze Trivelin, José Laércio Favarin,

Plant nutrient uptake and metabolism

Soybean [Glycine max (L.) Merr.] grain yield is closely associated with the level of optimal nitrogen (N) supply, especially during the reproductive stages. Foliar fertilization with low rates of N have been considered as a strategy for furnishing additional N and enhancing grain yields. Field studies using 15N tracer were conducted over two growing seasons to investigate the impact of foliar N fertilization on grain yield, plant N content, the amount of N derived from fertilizer (NDFF) and N recovery efficiency (NRE). Four foliar N rates (0, 1300, 2600 and 3900 g ha−1) were supplied by two equal split applications at the R1 and R3 stages. Foliar N fertilization of soybean canopies did not affect grain yield, grain N content, shoot N content nor plant N content. Total NDFF was increased from 0.7 to 2.0 kg ha−1 across the N rates. Nonetheless, NRE was unaffected by foliar N fertilization, which averaged 53 %. Soybean plants allocated the same amount of N fertilizer to both grains and shoots. No significant effects of low rate foliar N fertilization were registered on soybean grain yield nor plant N content, despite considerable N fertilizer recovery by plant organs.