The effects of tillage systems and crop rotations on soil chemical properties of a Black Chernozemic soil

The effects of zero (ZT), minimum (MT) and conventional tillage (CT) systems and three 4-yr crop rotations on soil total C and N, mineralizable N, NO 3 -N, P, K and SO 4 -S accumulation and distribution in the soil profile were determined after one 4-yr cycle of crop production on Black Chernozemic Indian Head heavy clay soil. The distributions of available P and K in the profile were not affected by tillage or rotation. Total C and N in the 0–5 cm depth was higher in the reduced tillage systems than in CT, but differences in the 5–10 cm and 10–15 cm depths were not significant. Nitrate concentration was higher in the 15–30 cm and 30–60 cm depths under CT than under reduced tillage. Inclusion of fallow increased accumulation of NO 3 -N in the deeper soil depths, while inclusion of winter wheat in the rotation reduced deep movement of NO 3 -N. Nitrate-nitrogen accumulation after field pea production was comparable to that after winter wheat, but a greater proportion of the NO 3 -N was present near the soil surface after winter wheat, reducing the potential for leaching below the rooting zone. Potential for movement of NO 3 -N below the rooting zone may be increased by fallow and decreased by production of winter wheat and by reduced tillage systems.