Cropping Systems Affect Wheat Yields, Nitrogen Use Efficiency, and Nitrous Oxide Emission

Abstract

Core Ideas Replacing chemical fallow with dry pea or camelina reduced wheat grain yield.Nitrogen fertilizer sources and tillage methods did not affect grain yield.The no‐till method improved grain protein yield in one of the two seasons.Agronomic nitrogen use efficiency improved with no‐till than sweep till.Sweep till and super urea tend to reduce the flux of N2O emission. Cropping systems include mainly cropping sequence, tillage, and fertilizer management practices. Information on the impact of these practices on yields, nutrient use efficiency, and greenhouse gas emission is limited. An experiment was conducted over a 2‐yr period in split‐split plot design to determine the effects of these practices on wheat (Triticum aestivum L.) grain and protein yields, agronomic nitrogen use efficiency (ANUE), and nitrous oxide (N2O) emission. The cropping sequences were chemical fallow–wheat (F‐W), dry pea (Pisum sativum L.)–wheat (P‐W), and camelina (Camelina sativa L. Crantz)–wheat (C‐W). Tillage methods were no‐till (NT) and sweep till (ST). Nitrogen fertilizer sources included urea (U) and Super U (SU), each applied at 0, 45, and 90 kg N ha−1. The result showed that the interaction of cropping sequence and tillage methods affected grain yield and ANUE in one of the two growing seasons. Replacing chemical fallow with dry pea or camelina reduced wheat grain yields by at most 15%, but the additional income from dry pea or camelina could offset this yield loss. Application of 45 kg N ha−1 increased grain yield and improved grain protein content compared with 0 kg N ha−1, regardless of N source. The highest protein yields (366 and 475 kg ha−1 in 2013 and 2014, respectively) were recorded at 90 kg N ha−1. The N fertilizer source had no effect on grain and protein yields and ANUE. The ST method and application of SU resulted in a lower flux of N2O emission than NT and U, respectively.