Northeastern China is a major maize-producing region, but decades of unsustainable tillage practices and excessive nitrogen fertilization have degraded black soils and threatened the sustainable production of maize. Conservation tillage practices based on straw return and reduced or no tillage are key approaches to improving soil quality and maintaining crop productivity, and optimizing nitrogen inputs is essential for enhancing resource-use efficiency. To determine suitable tillage practices and optimal nitrogen rates under straw incorporation, and to promote coordinated improvements in maize yield and soil quality in northeastern China, a fixed-site field experiment was conducted from 2022 to 2024 at Yanjiagang farm, Harbin, Heilongjiang province. The experiment used a split-plot design with tillage as the main-plot factor—conventional tillage (CT), rotary tillage (RT), strip tillage (ST), and no tillage (NT)—and nitrogen rate as the subplot factor: 0 (N0), 135 (N1), 180 (N2), and 225 kg hm-2 (N3) as pure N. Across the three years, mean grain yield ranked ST > CT > RT > NT, although differences among tillage treatments were not significant. Relative to NT, ST increased yield by 14.5% in 2023 and 6.6% in 2024, with no significant differences between ST and CT or RT. Nitrogen rate significantly increased yield (P ST > RT > CT, with significant differences among tillage treatments; NT was 20.2%-31.4% higher than CT. Both tillage and nitrogen rate significantly affected aggregate-size distribution, mean weight diameter (MWD), and geometric mean diameter (GMD) (P RT > ST > CT. The N2 and N3 treatments increased the proportion of 0.250-2.000 mm aggregates by 9.2%-29.7% and decreased the proportion of P -2. Overall, under straw incorporation, strip tillage combined with 180-225 kg hm-2 N can achieve high maize yield while improving soil aggregation, and is therefore recommended for the cold regions of northeastern China.
Ma et al. (Fri,) studied this question.
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