Abstract
Sustainable crop production systems can be attained by using inputs efficiently and nitrogen use efficiency (NUE) parameters are indirect measurements of sustainability of production systems. The objective of this study was to investigate the effect of selected nitrogen (N) management treatments on wheat yields, grain and straw N concentration, and NUE parameters, under conservation agriculture (CA). The present study was conducted at the International Maize and Wheat Improvement Center (CIMMYT), in northwest, Mexico. Seventeen treatments were tested which included urea sources, timing, and methods of fertilizer application. Orthogonal contrasts were used to compare groups of treatments and correlation and regression analyses were used to look at the relationships between wheat yields and NUE parameters. Contrasts run to compare wheat yields or agronomic efficiency of N (AEN) performed similarly. Sources of urea or timing of fertilizer application had a significant effect on yields or AEN (p > 0.050). However, methods of application resulted in a highly significant (p < 0.0001) difference on wheat yields and agronomic efficiency of N. NUE parameters recorded in this study were average but the productivity associated to NUE levels was high. Results in this study indicate that wheat grew under non-critically limiting N supply levels, suggesting that N mineralization and reduced N losses from the soil under CA contributed to this favorable nutritional condition, thus minimizing the importance of N management practices under stable, mature CA systems.
Highlights
One of the most limiting inputs in crop production and quality is nitrogen (N) [1]
In order to avoid redundancy, because yields having a direct relationship with agronomic efficiency of N (AEN), contrasts for yields are presented in Appendix A (Table A1) and are addressed while discussing nitrogen use efficiency (NUE) variables
Contrast 1, comparing both urea types was significant (p = 0.026) (Table A1), the absolute difference in yield was less than 200 kg ha−1, in favor of urea over NBPT-urea
Summary
One of the most limiting inputs in crop production and quality is nitrogen (N) [1]. N fertilizer that is not used to support crop production has the potential to cause a series of environmental issues such as eutrophication on water bodies, acid rain, N saturation in natural environments, and global warming [2,3]. Losses of N from agricultural systems negatively impact the environment as a result of poor N fertilizer management practices. This, in turn, results in low profitability to farmers [4,5]. Sustainable crop production systems, i.e., systems that take into account peoples wellbeing, farmers economy, and that are environmentally safe, can be attained by using inputs efficiently. Nitrogen use efficiency (NUE) and NUE components are indirect measurements of Agronomy 2018, 8, 304; doi:10.3390/agronomy8120304 www.mdpi.com/journal/agronomy
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