EFFICIENT USE OF NITROGEN IN SPLIT APPLICATIONS OF 15N-LABELED FERTILIZER IN WHEAT

The nitrogen use efficiency (NUE) by agricultural crops is very low due to losses associated with its high solubility and, in some soil conditions, due to high volatility, which results in negative impacts on economic profitability and environmental pollution. A field experiment was carried out under irrigation in soil of El Bajio, Guanajuato, Mexico to study the assimilation efficiency of nitrogen fertilizer by wheat (Triticum aestivum L.) by fractionating its application using ammonium sulfate enriched with 3.0237 % of atoms in excess of N-15 as a tracer. The Winter wheat varieties evaluated were Gema C2004, Nana F2007 and Urbina S2007; 100% of the fertilization rate was 240 kg N ha(-1) and 10 partitions in percentage were used at planting, stem elongation and heading (00-00-00, 100-00-00, 00-100-00, 50-50-00, 00-50-50, 70-30-00, 30-70-00, 00-30-70, 00-70-30 and 33-33-33). Yield and percentage of Nitrogen Use Efficiency (NUE) were higher when the N fertilizer was partitioned into 30-70-00, NUE ranged from 19.68 %, when partitioned at 100-00-00 and 41.14% when partitioned at 30-70-00. When N-fertilization was not applied at planting, the NUE was less than 25.72 %. In local practices, fertilization 50-50-00 is recommended, but yield increased up to 8.4 % and the NUE in grain up to 8.32 % when partition was 30-70-00. Proper fractionation of N-fertilization is necessary to improve nitrogen assimilation rates and grain quality.