Supplementary file 1_Local sediment and lime but no straw amendments can potentially improve barley biomass and yield at the field plot scale in Kenya.pdf

Soil acidification and nutrient leaching are major agricultural challenges in East Africa, leading to aluminum (Al) toxicity and poor crop yields. Various soil amendments are used worldwide to increase soil pH and crop production. Local sediment amendments have been identified as a potential soil improvement in Kenya, but the mechanisms remain unclear. This study examined the effects of liming, straw return, and local sediment amendments on nutrient availability and barley yield in Eldoret, Kenya. Plots were established with 1% and 3% of two local sediments (from Baringo and Nakuru) or with 0.15% lime, each with and without straw addition. Baringo 3% and lime treatments significantly reduced soil Al availability and increased soil pH, soil phosphorous (P) availability and barley yield (Baringo 3%: 1.3 t ha-1, Lime: 0.91 t ha-1), while the control had no yield. However, only Baringo 3% also increased soil silicon (Si) availability, achieving the highest yield. Other treatments and straw return had no significant impact on nutrient availability and plant production. These results indicate that the increase in barley yield with local sediment may be driven mainly by carbonate dissolution raising soil pH, while higher Si availability and accumulation could further enhance plant production. However, the beneficial effects are dependent on the sediment material and amendment rate.

土壤酸化与养分淋溶是东非地区面临的主要农业挑战，会引发铝（Al）毒害并导致作物减产。全球范围内广泛使用各类土壤改良剂以提升土壤pH值与作物产量。在肯尼亚，本地沉积物改良剂被视为一种具有潜力的土壤改良手段，但其作用机制仍未明确。本研究以肯尼亚埃尔多雷特地区为研究区域，探究了石灰施用、秸秆还田以及本地沉积物改良剂对土壤养分有效性与大麦产量的影响。试验设置了两种分别采自巴林戈（Baringo）和纳库鲁（Nakuru）的本地沉积物（施用比例为1%与3%）、0.15%石灰共四类处理，每组处理均设置添加秸秆与不添加秸秆两个亚组。其中，巴林戈3%比例沉积物处理与石灰处理可显著降低土壤铝有效性，同时提升土壤pH值、土壤磷（P）有效性以及大麦产量（巴林戈3%处理产量为1.3 t·ha⁻¹，石灰处理为0.91 t·ha⁻¹），而对照组未获得任何产量。但仅巴林戈3%比例沉积物处理可同时提升土壤硅（Si）有效性，最终获得最高产量。其余处理以及秸秆还田对土壤养分有效性与作物产量无显著影响。本研究结果表明，本地沉积物改良剂提升大麦产量的核心机制可能是碳酸盐溶解释放，进而提高土壤pH值；而更高的土壤硅有效性与硅素累积可进一步促进作物生产。不过，其改良效果取决于沉积物的材质与施用比例。