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NITROGEN MANAGEMENT

Strategies to Improve Nitrogen Use Efficiency in Winter Cereal Crops under Rainfed Conditions

^a Dep. Producción Agraria, Universidad Pública de Navarra, Campus Arrosadía s/n 31006 Pamplona, Spain
^b Dep. Producción Vegetal: Fitotecnia, ETSIA, Univ. Politécnica de Madrid, Avda Complutense s/n 28040 Madrid, Spain

^* Corresponding author (miguel.quemada{at}upm.es).

Developing fertilizer strategies that increase nitrogen use efficiency (NUE) could reduce unnecessary input costs to farmers and environmental impact of N losses. Two field experiments were performed in northern Spain to evaluate alternative N fertilization strategies to improve NUE in winter cereal crops (wheat [Triticum aestivum L.] and barley [Hordeum vulgare L.]). The strategies were: (i) adjusting the fertilizer rate by soil mineral N before N application; (ii) splitting of N fertilizer application; and (iii) the use of fertilizer with a nitrification inhibitor (3,4-dimethylpyrazole phosphate, DMPP). The experiments were designed as a completely randomized block design with seven treatments and four replications. Treatments included a control, two single applications, one with DMPP, and four split N applications. Nitrogen balance was calculated according to the general equation of conservation of mass for any soil–crop system from which N-efficiency parameters were determined. Grain yield followed a quadratic-plus-plateau model with different optimum N rate depending on the year (71 and 98 kg N ha^–1 in 2002–2003 and 2003–2004, respectively). Adjusting N fertilizer rate by soil mineral N before N application gave a maximum yield and a similar NUE to the optimum N rate predicted by the model. Neither applying N in two doses nor including a nitrification inhibitor with a single dose showed any advantages in terms of yield or N efficiency.

Abbreviations: ASN, ammonium sulfonitrate • GLAI, green leaf area index • N_a, organic nitrogen in aboveground plant parts • N_bal, nitrogen balance • N_f, nitrogen supplied by fertilizer • N_h, soil mineral nitrogen at harvest • NI, nitrification inhibitor • N_ini, soil mineral nitrogen at sowing • N_lch, nitrogen leached • N_m, mineral nitrogen supplied by soil • N_r, organic nitrogen in roots • NRF, nitrogen recovery fraction • NUE, nitrogen use efficiency • NU_pE, nitrogen uptake efficiency • NU_tE, nitrogen utilization efficiency

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Received for publication June 3, 2007.