For exploring the regulation effect of strip subsoiling (SS) on spatial distribution and amount of maize population root system, a field experiment was conducted with three planting densities (LD: 45 000 plants ha-1, MD: 67 500 plants ha-1, 90 000 plants ha-1) and two soil tillage practices (SS: strip subsoiling tillage, NT: no tillage). The spatial distribution of maize individual and population roots and its response to planting density and soil tillage were studied using small cubic root soil sampler through the “3D monolith” root space sampling method. The result indicated that individual root length was significantly affected by planting density. In 0–50 cm soil layers (each layer was 10 cm), individual roots length was decreased by 110.31, 43.18, 15.73, 10.49, and 17.45 m under high planting density compared with under low planting density. Under the condition of high planting density, strip subsoiling increased individual roots length by 13.32%, 19.80%, 47.20% in 20–30 cm, 30–40 cm, 40–50 cm soil layers compared with no tillage. The effects of planting density were not significant on population total root length, while significant on spatial distribution of population root system. The root length density around single plant centre was decreased by 3.82 cm cm-3, 0.62 cm cm-3 in 0–10 cm, 10–20 cm soil layers, while root length density between two plants was increased by 1.13 cm cm-3, 0.18 cm cm-3, 0.06 cm cm-3, 0.05 cm cm-3 in 0–10 cm, 10–20 cm, 20–30 cm, 30–40 cm soil layers under high planting density compared with under low planting density. Under the condition of high planting density, compared with no tillage, strip subsoiling decreased root length density around single plant centre by 16.10% in 0–10 cm soil layer, while increased it by 47.45%, 13.37% in 10–20 cm, 20–30 cm soil layers. Meanwhile, strip subsoiling increased root length density between two plants by 50.26%, 30.72%, 106.15% in 20–30 cm, 30–40 cm, 40–50 cm soil layers respectively. The significant change of spatial distribution of population root system increased the index of root surface area and root dry matter in high planting density and strip subsoiling tillage treatment. The increments in leaf area and shoot dry matter resulted in an increment of maize final yield. The results of this study suggest that the distribution of root between two plants is improved with the increment of planting density. The treatment of high planting density and strip subsoiling regulates the spatial distribution of population root system by increasing the root quantity in deep soil layer and between two plants, and weakening the crowding of roots in up soil layer, which promotes the increment of maize yield.
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