Soil changes over 12 yr of conventional vs. conservation management on irrigated rotations in southern Alberta

Increased irrigated production of potato (Solanum tuberosum L.), dry bean (Phaseolus vulgaris L.), and sugar beet (Beta vulgaris L.) in southern Alberta in the 1990s prompted a 12 yr (2000–2011) study to evaluate conservation (CONS) management practices for these crops in 3–6 yr rotations. Conservation management included reduced tillage, cover crops, compost, and narrow-row dry bean. After 12 yr, soil organic carbon (SOC) at 0–30 cm depth increased by 0.48 Mg ha−1 yr−1 on a 5 yr CONS rotation, in line with average cumulative compost addition of 154 Mg ha−1. In contrast, SOC stocks on a 3 yr conventional (CONV) rotation, which did not receive compost, declined by 0.25 Mg ha−1 yr−1. Nitrate-N did not accumulate in the soil profile under CONS management, as it was largely influenced by previous crop. In contrast, available P increased with compost addition under CONS management, leading to surface buildup and downward movement in the soil profile. At 0–120 cm depth, the CONS rotations showed 26%–53% higher ...