Efficiency of N uptake by wheat,as affected by time and rate of application,using N15-labelled ammonium sulphate and sodium nitrate

Summary The efficiency of N uptake by wheat was studied in field experiment, using N¹⁵-labelled (NH₄)₂SO₄ and NaNO₃. The N rate used was 120 kg N/Ha. It was applied in three split doses (at seeding, tillering and boot stage), in two split doses (at seeding and tillering stage) and in a single dose at seeding.The N applied at seeding, tillering and boot stage was actively used by wheat. However N applied at tillering stage was utilized most effectively. The single application of N was least productive for grain yield. Splitting the N fertilization increased the efficiency of applied N. The NO₃–N was most productive when applied in three split applications and produced significantly higher yield than single application. The NH₄–N was not as effective and its splitting beyond two doses did not benefit wheat. The A values and calculated effective rate of application (E.R.A.) also established the superiority of NO₃–N over NH₄–N. The E.R.A. proved useful in evaluating time of application as well.