Diversifying cropping systems enhances productivity, stability, and nitrogen use efficiency

Long-term field experiments are useful for determining cropping system productivity, stability, and resource use efficiency. With 12 yr (2004-2015) of data from five cropping systems on a long-term experiment (> 30 yr) under semiarid conditions in Saskatchewan, Canada, a systems-approach was used to compare grain and protein yield, stability, nitrogen (N) dynamics, N fertilizer (FUEG,P), and available N use efficiency (NUEG,P) for grain and protein. Annualized grain and protein yields for wheat (Triticum aestivum L.)-canola (Brassica napus L.)-wheat-field pea (Pisum sativum L.; W-C-W-P) were 2244 and 372 kg ha(-1), respectively, 14 to 38% and 33 to 66% higher, respectively, than continuous wheat (ContW), summer fallow-wheat-wheat-wheat (F-W-W-W), F-W-W, and lentil (Lens culinaris Medik) green manure-wheat-wheat (GM-W-W). Fallow systems were the most stable, but less productive and well-adapted to low-yielding conditions, while GM-W-W was the least stable and poorly adapted. The ContW had below-average stability and was better suited to high-yielding conditions for grain. The W-C-W-P consistently produced above-average yields, and was best suited for high-yielding conditions for grain and protein. The ContW and W-C-W-P had the highest NUEG (26.4 g kg(-1)) and NUEP (4.1 g kg(-1)), respectively, with GM-W-W having the lowest (18.1 and 2.7 g kg(-1)); FUE was the reverse of NUE. This long-term study showed that diversified cropping systems that include pulses can more consistently produce higher grain and protein yields, regardless of growing conditions, than most other systems with lower N fertilizer inputs, thereby potentially reducing the negative environmental consequences associated with N fertilizer application.