Restoring soil carbon (C) lost due to intensive farming is a long-term endeavor under current conservation management practices. Application of coal combustion residue (293 g C kg-1 ) from a sugar beet (Beta vulgaris L.) processing factory, hereafter referred to as char, could rapidly restore soil C and productivity in degraded croplands, but data on this potential strategy are unavailable. We assessed the impacts of char application to two relatively low-C soils (10.1 and 12.2 g C kg-1 ) and one relatively high-C soil (17.3 g C kg-1 ) on soil C, soil physical and fertility properties, and crop yields in no-till systems in the Great Plains after 2 yr. Char was disked to 15 cm soil depth at char-C application rates ranging from 0 to 19.7 Mg C ha-1 , corresponding to char application rates ranging from 0 to 67.3 Mg ha-1 . The highest char rate increased C concentration in all soils but increased C stock only in low-C soils. Char did not affect soil penetration resistance, available water, aggregate stability, most nutrients, and crop yields. Char application at high rates increased sulfate, Ca, Mg, and Na concentrations but did not influence other properties. Carbon recovery of the char applied at the highest rate varied among soils from 50 to 85%, but the mechanisms for such differences need further investigation. Short-term duration, low char C concentration, and low application rates may explain the limited char effects. Overall, char application at 19.7 Mg char-C ha-1 (i.e., 67.3 Mg char ha-1 ) increased soil C concentration but had negligible effects on other soil properties and crop yields after 2 yr.

中文翻译：

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炭碳能否增强低碳土壤中的土壤特性和作物产量？两年后的感悟

在当前的保护管理实践下，恢复因集约化耕作而损失的土壤碳 (C) 是一项长期努力。使用来自甜菜 (Beta vulgaris L.) 加工厂的煤燃烧残渣 (293 g C kg-1 )，以下称为炭，可以快速恢复退化农田的土壤碳和生产力，但有关这种潜在策略的数据是不可用。我们评估了炭对两种碳含量相对较低的土壤（10.1 和 12.2 g C kg-1 ）和一种碳含量相对较高的土壤（17.3 g C kg-1 ）对土壤碳、土壤物理和肥力特性的影响，以及2 年后大平原免耕系统的作物产量。在 0 到 19.7 Mg C ha-1 范围内的炭碳施用率下，炭被盘到 15 cm 土壤深度，对应于范围从 0 到 67.3 Mg ha-1 的炭施用率。最高的炭化率增加了所有土壤中的碳浓度，但仅增加了低碳土壤中的碳储量。炭不会影响土壤渗透阻力、可用水、团聚体稳定性、大部分养分和作物产量。高比例的炭应用增加了硫酸盐、Ca、Mg 和 Na 的浓度，但不影响其他特性。以最高速率施用的炭的碳回收率在土壤中从 50% 到 85% 不等，但这种差异的机制需要进一步研究。短期持续时间、低炭 C 浓度和低施用率可以解释有限的炭效应。总体而言，施用 19.7 Mg char-C ha-1（即 67.3 Mg char ha-1）的炭会增加土壤 C 浓度，但对其他土壤性质和 2 年后作物产量的影响可以忽略不计。