Long-term reduced and no tillage increase maize (Zea mays L.) grain yield and yield stability in Northeast China

The stability of maize production in Northeast China where rain-fed agriculture is widely practiced faces serious challenges due to climate change. Therefore, to investigate how the mechanisms of conservation tillage affect maize yield, a 4-y study (2018–2021) with two planting densities (60,000 and 90,000 plants ha−1) and three tillage treatments (CT: conventional tillage; RT: reduced tillage; NT: no tillage) was conducted in a 39-y, long-term field experiment. Under 60,000 plants ha−1, maize grain yield was 13.8% higher in NT and 19.6% higher in RT than in CT, whereas under 90,000 plants ha−1, yields were 10.6% higher in NT and 12.6% higher in RT. Reduced and no tillage increased yields compared with those in CT by increasing harvesting ears, kernels per ear, and 1,000-kernel weight. Compared with CT, long-term RT also increased the harvest index under both planting densities, whereas NT only increased the harvest index under 60,000 plants ha−1. Compared with CT, long-term RT and NT increased maize plant height, canopy radiation interception rate, and leaf photosynthetic physiology (i.e., photosynthetic rate, maximal quantum yield of photosystem II photochemistry and actual photochemical efficiency of photosystem II). However, radiation and temperature production efficiency were not different among tillage treatments at either plant density, an interesting target when further improving yield level and stability. Based on the results, RT and NT are recommended to be integrated into crop cultivation strategies for rain-fed agriculture in Northeast China, which is expected to mitigate the adverse effects of increased climatic challenges.