Slope gradients mediate the effects of newly returned crop residues on soil nutrient dynamics and microbial diversity in Mollisol maize monoculture systems in Northeast China - Anwar Zeb; Liang-Jun Hu; Xu Li; Gohar Ali; Atteqa Akbar; Sarfraz Ahmed; Muhammad Awais Haider; Amrozia Naz (Agriculture, Ecosystems & Environment, 2026)