Molybdenum‐induced effects on nitrogen uptake efficiency and recovery in wheat (<i>Triticum aestivum</i>L.) using¹⁵N‐labeled nitrogen with different N forms and rates

Abstract

Abstract Background : Molybdenum (Mo) is an essential microelement for higher plants and plays a significant role in nitrogen (N) metabolism, which includes nitrate reduction, assimilation, and efficient N acquisition. Its deficiency in soil may induce the reduction of N uptake and wheat yield. Aims : We aimed to explore the Mo‐induced effects on N uptake efficiency and recovery in Mo‐inefficient winter wheat cultivar using a 15 N isotope tracer under different N forms (Nf) and N rates (Nr). Methods : The experiment was conducted in greenhouse conditions, and the treatments included three Nf in the form of 15 NH 4 Cl as sole NH 4 + , Ca ( 15 NO 3 ) 2 as sole NO 3 − , and 15 NH 4 15 NO 3 ) under two Nr [low (L) 0.05 and high (H) 0.25 g N kg –1 soil], with (+Mo) in form of [(NH 4 ) 6 Mo 7 O 24 ∙ 4H 2 O] and without (–Mo) Mo application. The plant biomass, Mo content, total N uptake, fertilizer 15 N uptake, soil N uptake, as well as N uptake, agronomic and physiological efficiency were evaluated. Furthermore, the fertilizer 15 N recovery in various wheat organs was also studied. Results : The results revealed that Mo application increased N uptake efficiency in wheat to 38.26%, 68.24%, and 71.53% when the plants are treated with low rates of NH 4 + , NO 3 − , and NH 4 NO 3 , respectively. While at a high N rate, N uptake efficiency increases to 46.26% and 45.34% in the case of NO 3 − and NH 4 NO 3 treatments, respectively, and it was slightly reduced to 10.84% when plants were supplied with NH 4 + form. Mo supply increased 15 N recovery from fertilizer in grain organ under low N rate with all supplied Nf, that is, NH 4 + , NO 3 − , and NH 4 NO 3 , while at high N rate, Mo enhanced 15 N recovery in grains organ in case of NO 3 − and NH 4 NO 3 forms. Conclusion : This study shows that Mo fertilization may be a promising strategy to improve N uptake efficiency and recovery in wheat when nitrate is the main N form.