A. Matus

The influence of tillage and crop rotation on nitrogen fixation in lentil and pea

Direct seeding into standing stubble and crop diversification are two practices that are becoming widely adopted in western Canada. This study was conducted to determine: i) the influence of zero and conventional tillage on N-fixation in lentil (Lens culinaris Medikus) and pea (Pisum sativum L.), and ii) the effect of cropping history on N-fixation in lentil. Data were obtained from a crop rotation experiment being conducted on a silty clay soil in east-central Saskatchewan, which included six cereal-oilseed-cereal-pulse rotations, each managed using zero and conventional tillage practices. The finding showed that N-fixation was 10% higher by lentil and 31% higher by pea when grown using zero tillage as compared to conventional tillage practices. On average, lentil grown in highly diversified crop rotations fixed 12% more nitrogen than when grown in less diversified crop rotations. Key words: Nitrogen fixation, lentil (Lens culinaris Medikus), pea (Pisum sativum L.), zero tillage, conventional tillage

Carbon isotope discrimination and indirect selection for transpiration efficiency at flowering in lentil (Lens culinaris Medikus), spring bread wheat (Triticum aestivum L.) durum wheat (T. turgidum L.), and canola (Brassica napus L.)

SummaryCarbon isotope discrimination has been proposed to indirectly select for transpiration efficiency in several C3 species. To determine the effectiveness of carbon isotope discrimination to indirectly select for transpiration efficiency at flowering we measured: (i) variability for carbon isotope discrimination, (ii) the magnitude of the genotype-by-water regime interaction for carbon isotope discrimination, and (iii) the magnitude of the correlation between carbon isotope discrimination and both transpiration efficiency and dry matter at flowering. Ten lentil (Lens culinaris Medikus) genotypes, ten wheat genotypes (eight spring wheat (Triticum aestivum L.) and two durum wheat (Triticum turgidum L.)), and ten canola (Brassica napus L.) genotypes were grown in a greenhouse at 80, 50 and 30% field capacity. Above ground dry matter was harvested at 80% flowering and dry matter at flowering, water used, and carbon isotope discrimination determined. Genotype variation for carbon isotope discrimination was observed in lentil, spring wheat and canola at each water regime, and when averaged over the three water regimes. The largest range in carbon isotope discrimination among lentil and spring wheat genotypes was observed using the wet regime; whereas, the dry regime provided the largest range for CID in canola genotypes. In all species the genotype-by-water regime interaction for carbon isotope discrimination was nonsignificant. The correlation between carbon isotope discrimination and dry matter at flowering was inconsistent across water regimes and years. In addition, in all three crops, no correlation was observed between carbon isotope discrimination and transpiration efficiency at any of the water regimes, and when averaged over water regimes and years. These results suggests that under the conditions reported here, carbon isotope discrimination cannot be used effectively to indirectly select for transpiration efficiency in lentil, spring wheat, and canola.

Comparison of a dual‐inlet gas isotope ratio mass spectrometry system and an automated single‐inlet mass spectrometry system for δ13C analysis

Abstract A dual‐inlet isotope ratio mass spectrometer (VG‐SIRA 12, Isotech, Middlewich, England) using sealed‐glass combustion sample preparation and an automated single‐inlet isotope ratio mass spectrometry system (RoboPrep Sample Converter interfaced with a TracerMass Stable Isotope Detector, Europa Scientific, Crewe, England) were compared for δ13C analysis. Two hundred twenty four samples of plant and animal tissue were analyzed for S13C using the two systems. Delta 13C values obtained from the two instruments were highly correlated (r2=0.986, P=0.0001). The slope of the relationship was not different from one nor was the Y‐intercept different from zero (Y=‐0.2 + 1.0X; P=0.86 and P=0.28 for the slope and Y‐intercept, respectively). In addition, samples from two complete experiments were run on both mass spectrometery systems and statistical analyses performed. In both experiments, differences between treatments were detectable using the RoboPrep system that were not detectable using the SIRA 12 system...