The results from the last three years at the AFIF Swift Current spoke site have shown that the yield of AC Barrie hard red spring wheat on pea, lentil, or Kabuli chickpea stubble has averaged 5 to 8 bushels per acre more than AC Barrie on durum stubble (see Figure 1). This yield benefit after a pulse crop occurred across a range of N fertilizer rates -- when applying less fertilizer than soil-test recommended (25 to 30 lb/ac of actual N), applying soil-test recommended fertilizer N (40 to 45 lb/ac of actual N) or applying more fertilizer than recommended (65 to 70 lab/ac N actual). Wheat grain protein has also averaged 0.5 to 1 percentage points higher on pea or lentil stubble than on durum stubble (see Figure 2). Again, the protein benefit after a pea or lentil was about the same across a range of rates of N fertilizer. Wheat grain protein after Kabuli chickpea was about the same as after durum except at highest N rate when protein after chickpea was about a percentage point higher than after durum. At the lowest N fertilizer rate, the AC Barrie yield and protein was about the same on oriental mustard stubble as on durum stubble. However, at soil-test recommended or higher N rate, AC Barrie yielded 2 to 5 bu/ac more and had 0.2 to 0.5 percentage points higher protein on mustard stubble than on durum stubble. However, the AC Barrie did not always do better on the stubble of a broadleaf crop than on cereal stubble. When planted on coriander stubble, the wheat often did worse than on durum stubble, particularly at high N fertilizer rates.
Durum (Kyle) and Canadian Prairie Spring wheat (AC Karma) were very similar to hard red spring wheat with regard to their relative yield and protein performance for the different stubble types and for different N fertilizer rates. Yield and protein were highest on pea and lentil stubble and lowest on coriander and durum stubble. If the yield was higher on mustard and chickpea stubble than the protein was usually similar to that on durum stubble. However, if the yield was the same on mustard and chickpea stubble as on durum stubble, then the protein was higher.
The yield and protein increase for each additional amount of N fertilizer applied was similar among stubble types for durum and both wheats. Hence, there is no reason to reduce N fertilizer to below soil-test recommendations for pulse stubble. In fact, considering protein premiums, under fertilizing wheat on pulse stubble can be a poorer decision than under fertilizing wheat on other stubble. For example, in 1999 and 2000, we did not capture the protein premium for durum on durum stubble even with 70 lb/ac of actual N. We only attained high-protein durum when it was grown on pea or lentil stubble and fertilized to soil-test recommendations or better.
Figure 1. Average yield of AC Barrie for 1998 to 2000 at the AFIF Swift Current spoke site as affected by previous stubble and nitrogen fertilizer rate.
Figure 2. Average protein of AC Barrie for 1998 to 2000 at the AFIF Swift Current spoke site as affected by previous stubble and nitrogen fertilizer rate.