Limited information is available on soil management effects on crop production and nitrogen (N) cycling in acid soils. The effects of conventional tillage (CT) versus no-till (NT) and liming (0 versus 7.5 Mg ha -1), and their interaction, on labile N pools in an acid soil were evaluated during the 7th to 10th year of a 3-course small grain rotation. Crop production and N uptake, N 2 fixation by pea ( Pisum sativum L.), and labile soil N were determined. Liming increased the pH from 5.3 to 6.0 in the top 10 cm of soil and had no influence below 10 cm depth. No-till increased average crop yield and N uptake by 12 and 14%, respectively, compared to CT. The corresponding increases due to lime application were 13 and 20%. There was no treatment effect on N concentrations in plant tissues (probably because of adequate N fertilizer application), or on N 2 fixation in pea. The percent N derived from the atmosphere varied from 12% in one dry year to 68% in a moister year. Soil NO 3 in spring and autumn was significantly higher where the preceding crop was field pea, particularly in the surface soil layer. Soil inorganic N was little influenced by tillage and liming. In contrast, soil microbial biomass N concentration was consistently greater with liming than without (30-64% difference) and with NT than with CT (7-36% difference), but little affected by crop sequence. Liming enhanced the positive effect of NT on soil microbial biomass N. Crop total N uptake was significantly correlated with microbial biomass N ( r=0.69* for barley ( Hordeum vulgare L.), and 0.70** for canola ( Brassica rapa L.)). Liming with NT can be effective in increasing N turnover and crop growth in acid soils.
