To determine farm C credit and reduce global warming potential, information is needed on the effect of management practices on soil C storage. The effects of tillage, cropping sequence, and N fertilization were evaluated on dryland crop biomass, surface residue C, and soil organic carbon (SOC) at the 0- to 120-cm depth in a Williams loam (fine-loamy, mixed, superactive, frigid, Typic Argiustolls) and their relationships with grain yields from 2006 to 2011 in eastern Montana. Treatments were no-till continuous malt barley ( Hordeum vulgare L.) (NTCB), no-till malt barley-pea ( Pisum sativum L.) (NTB-P), no-till malt barley-fallow (NTB-F), and conventional till malt barley-fallow (CTB-F), each with 0, 40, 80, and 120 kg N ha -1. Annualized crop grain and biomass yields, surface residue amount, and C contents were greater in NTB-P and NTCB than CTB-F and NTB-F and increased with increased N rates. At 0 to 5 and 5 to 10 cm, SOC was greater in NTB-P than CTB-F or NTCB with 40 kg N ha -1 and at 10 to 30 and 0 to 120 cm was greater in NTB-P than NTCB with 120 kg N ha -1. Surface residue C and SOC were related with grain yield and C content ( R2=0.21-0.55, P?0.10, n=16). Greater amount of crop residue returned to the soil and turnover rate probably increased surface residue C, soil C storage, and crop yields in NTB-P with 40 and 120 kg N ha -1 than the other treatments. Soil organic matter and crop yields can be enhanced by using NTB-P with 40 kg N ha -1.
