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Effect of Time of Application of the First Dose of Nitrogen on Yield and Fertilizer Use Efficiency in Maize Grown in Calcareous Soils

ABSTRACT Application of a basal dose of fertilizer nitrogen (N) at sowing of maize has been always practiced in general recommendations in Egypt and elsewhere. A field experiment in two consecutive years (2015 and 2016) was conducted to assess the usefulness of application of a dose of N fertilizer at sowing of maize in calcareous soil at West Delta, Egypt. The treatments consisted of N fertilizer levels of 0, 240, 280, and 320 kg N ha−1 applied in three equal split doses. The first dose for each level was practiced at 0, 7, 14, and 21 days after sowing (DAS). The results indicated that practicing the first dose of N fertilizer at 0 or 7 DAS resulted in highest normalized difference vegetation index (NDVI) at early growth stage. However, the NDVI at later stages dramatically modified to reach highest when practicing the first dose at 14 or 21 DAS. Grain yields of maize when applying the first dose at 14 or 21 DAS were always significantly higher than when applied at 0 or 7 DAS. This was consistent with N fertilizer-use efficiencies. By just postponing the first dose of N from 0 to 14 DAS resulted in an increase of 7.7–13.5% in recovery efficiency and 1.1–2.7 kg grain kg−1 N in agronomic efficiency in both seasons. This study evidenced that application of N fertilizer early at sowing of maize is not necessary as it could resulted in low N-use efficiency.