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Crop roots are an important source of organic matter in agricultural soils. Assessing the potential of crop root biomass and nutrient resources can help optimize fertilizer and irrigation management strategies and provide scientific support for improving soil structure and quality. This paper combines data from the literature, establishes an indicator parameter system for crop root-to-straw ratio, and based on the 2022 national crop straw resource account data, measures the root biomass of China’s major crops in detail, and analyses the effective nutrient resources and fertilizer substitution potential of the root system in the current season. In 2022, the total root biomass of major crops nationwide was 152 million tons, accounting for 18.63% of the straw production. The root biomass of rice, wheat, and corn alone comprised 90.2% of the total. The total nutrient resource amount from the underground root systems of these crops was 3.22 million tons, with an effective nutrient resource amount of 2.32 million tons for the growing season. Specifically, the effective nutrient resource amounts per unit area for N, P 2 O 5 , and K 2 O were 4.71 kg/ha, 1.39 kg/ha, and 12.85 kg/ha, respectively. The effective nutrient resources of the main crop roots in the season accounted for 5.31% of the best chemical fertilizer application amount, which was equivalent to 2.62% of the N fertilizer application amount, 1.76% of the P 2 O 5 fertilizer application amount and 13.09% of the K 2 O fertilizer application amount. Crop roots are rich in nutrient resources and the contribution of their roots to soil carbon sequestration is considerable.

A pot experiment was conducted to study interactive effects of arbuscular mycorrhizae (AMs) and maize (Zea mays L.) straws on wheat (Triticum aestivum L.) growth and organic carbon (C) storage in a sterilized sandy loam soil. The experiment included four treatments: control, inoculation with AM fungus Glomus caledonium (M), amendment with maize straw (S), and amendment with maize straw plus inoculation with G. caledonium (S + M). The inoculation of G. caledonium significantly (P < 0.05) increased wheat root biomass and root-to-straw ratio, but had no significant effects on shoot biomass, grain yield, and soil parameters. The amendment of maize straw significantly (P < 0.05) decreased soil pH, wheat root biomass, and root-to-straw ratio, and significantly (P < 0.05) increased soil invertase and alkaline phosphatase activities, but had no significant effects on shoot biomass, grain yield, soil organic C content, and urease activity. The combined application of G. caledonium and maize straw had no significant effects on root mycorrhizal colonization rate compared to the M treatment, while significantly (P < 0.05) increased wheat root biomass and significantly (P < 0.05) decreased soil pH compared to the S treatment, and also significantly (P < 0.05) increased grain yield, soil organic C content, and urease activity compared to the control. The Two-Way ANOVA also showed interactive effects of G. caledonium and maize straw on soil pH (P < 0.05) and wheat grain yield (P < 0.01), and the redundancy analysis result indicated the potential application of AM fungi in straw-returned fields.