Nitrogen economy of early and late-sown maize crops

• Published in: Field crops research 2019-02, Vol.231, p.40-50
• Main Authors: Maltese, N.E., Melchiori, R.J.M., Maddonni, G.A., Ferreyra, J.M., Caviglia, O.P.
• Format: Article
• Language: English
• Subjects: Maize; Nitrogen uptake efficiency; Nitrogen use efficiency; Nitrogen utilisation efficiency; Sowing date
• ISSN: 0378-4290; 1872-6852
• DOI: 10.1016/j.fcr.2018.11.007

•We compared nitrogen use efficiency (NUE) and its components (NutE and NupE) of early and late-sown maize crops.•NUE and NutE (nitrogen utilization efficiency) decreased as sowing date was delayed.•NupE (nitrogen uptake efficiency) accounted for a higher proportion of the variation in NUE than NutE.•In late sowing date, NupE was mainly related to pre-flowering N uptake.•NutE decreased when post-flowering N source per grain was increased. Late sowing dates of maize are widely adopted in the Pampas region of Argentina, stabilising grain yields due to a more favourable water balance around flowering. However, late-sown crops are exposed to high soil N availabilities (Nav), high temperatures during the pre-flowering period and declining photo-thermal conditions during grain filling, which may affect nitrogen use efficiency (NUE, kg of grain per kg of Nav). These effects could be exerted through nitrogen uptake efficiency (NupE, kg of N uptake per kg of Nav) and/or nitrogen utilisation efficiency (NutE, kg of grain per kg of N uptake). Environmental conditions could affect i) pre (Nuptpre) and/or post-flowering N uptake (Nuptpost) and, consequently, NupE and ii) the determinants of NutE, such as N harvest index (NHI) and N source per grain. Early- and late-sown maize were cropped in order to analyse i) grain yield, Nav and NUE and ii) relationships among NUE and related-N efficiencies. The experiments were carried out in Paraná (31°48′ S 60°32′ W), Argentina, during 2014–2015 and 2015–2016. Treatments were combinations of two sowing dates (early and late), three N rates (0, 90, and 270 kg N ha−1) and two genotypes (DK 70-10 VT3P and DK 73-10 VT3P). NUE decreased in late-sown crops (ca. 32 to 26 kg grain kg Nav−1), mediated by lower grain yields (ca. 8564 kg ha−1 and 7832 kg ha−1 in early- and late-sown crops, respectively) and higher Nav (ca. 267–312 kg Nav ha−1). DK 73-10 VT3P exhibited the highest NUE (ca. 31 kg grain kg Nav−1) and NutE (ca. 63 kg grain kg Nupt−1). N rate affected more strongly Nav than grain yield; and there was a greater association between NUE and NupE (P