Eight-year tillage in black soil, effects on soil aggregates, and carbon and nitrogen stock.

The effects of different tillage management practices on the soil aggregates, soil carbon stock (STCS), and soil nitrogen stock (STNS) are key issues in agricultural research. We conducted an 8-year field experiment to evaluate the effects of different tillage methods: stubble cleaning and ridging (CK), no-tillage with stubble retention (NT), plow tillage (PT), and width lines (WL) on soil aggregates, STCS, and STNS in the black soil corn continuous cropping area of Northeast China. Different tillage methods predominantly affected the soil aggregates in the 2-0.25 mm and 0.25-0.053 mm size classes. The PT methods increased the proportion of macroaggregates and improved the quality of the soil aggregates. PT methods significantly increased the soil organic carbon content at the 0-30 cm layer by changing the number of soil macroaggregates. The PT practices are better strategies for enhancing soil carbon sinks, and the WL method increased the total amount of N in the soil pool. Our results suggest that the PT and WL methods are the best strategies for improving the quality of soil aggregates and preventing/reducing depletion of soil C and N in a black soil area of Northeast China.