Silicate fertilizer derived from iron slag (hereafter, silicate fertilizer) as a soil amendment has been added to Korean and Japanese rice paddies to improve soil pH and supply nutrients to the crop. However, the consequences of silicate fertilizer application to soil organic carbon (SOC) stocks remain unclear. Hypothetically, silicate fertilizer might deplete SOC by increasing soil pH and stimulating microbial activity or increase SOC by improving rice productivity and biomass. To investigate this, we first quantified the relationship between plant-available silicate (SiO) and soil organic matter concentrations using national soil survey data. We found a highly positive correlation between the two parameters, suggesting that long-term silicate fertilizer application might promote SOC sequestration. We then examined the effect of silicate fertilizer and lime (CaCO) addition on soil respiration for 30 days under flooded conditions. Both materials increase soil pH but affect soil respiration in different ways: respiration increased significantly with lime but decreased significantly with silicate fertilizer application. This demonstrates that silicate fertilizer simultaneously improves pH while minimizing C loss through soil respiration. Finally, in a field study spanning two years, we ascertained the impact of silicate fertilizer (1.5 Mg ha) on annual SOC stock changes under rice cropping. Silicate fertilizer application increased net primary production (NPP) of rice plants by around 20% over control plots that did not receive silicate but decreased respired C loss by 16–20%. As a result, silicate fertilizer application increased the SOC stock by 0.96–1.1 Mg C ha year over the control. Our findings show that iron slag-based silicate fertilizer can promote C sequestration in soil organic matter while simultaneously improving soil properties and rice productivity.

中文翻译：

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水稻土施用铁渣基硅酸盐肥增加土壤有机碳储量

来自铁渣的硅酸盐肥料（以下简称硅酸盐肥料）作为土壤改良剂已被添加到韩国和日本的稻田中，以改善土壤pH值并为作物提供养分。然而，施用硅酸盐肥料对土壤有机碳（SOC）储量的影响仍不清楚。假设，硅酸盐肥料可能通过增加土壤 pH 值和刺激微生物活性来消耗 SOC，或者通过提高水稻生产力和生物量来增加 SOC。为了调查这一点，我们首先使用国家土壤调查数据量化了植物有效硅酸盐（SiO）和土壤有机质浓度之间的关系。我们发现这两个参数之间存在高度正相关性，表明长期施用硅酸盐肥料可能会促进有机碳固存。然后，我们在淹水条件下研究了 30 天的硅酸盐肥料和石灰 (CaCO3) 添加对土壤呼吸的影响。这两种材料都会增加土壤 pH 值，但以不同的方式影响土壤呼吸：施用石灰时呼吸显着增加，但施用硅酸盐肥料时呼吸显着降低。这表明硅酸盐肥料可同时改善 pH 值，同时最大限度地减少土壤呼吸造成的碳损失。最后，在一项为期两年的实地研究中，我们确定了硅酸盐肥料（1.5 毫克公顷）对水稻种植下年度有机碳库变化的影响。与未施用硅酸盐的对照地块相比，施用硅酸盐肥料使水稻植株的净初级生产力（NPP）增加约20%，但呼吸性碳损失减少了16-20%。结果，施用硅酸盐肥料使 SOC 储量比对照增加了 0.96-1.1 Mg C ha 年。我们的研究结果表明，铁渣基硅酸盐肥料可以促进土壤有机质中的碳固存，同时改善土壤性质和水稻生产力。