Nyuma Henry Tamba, Njoroge Ruth, Otinga Abigael Nekesa
Department of Soil Science, School of Agriculture & Biotechnology, University of Eldoret, Eldoret, Kenya.
Department of Agronomy, College of Agriculture & Forestry, University of Liberia, Monrovia, Liberia.
PLoS One. 2025 Apr 8;20(4):e0313385. doi: 10.1371/journal.pone.0313385. eCollection 2025.
Agroforestry, a sustainable land use practice, was introduced in western Kenya in the early 1990s as a soil fertility replenishment strategy. Since then, the effect of the practice on soil quality has seldom been evidenced. A study was conducted to assess the impact of agroforestry adoption on soil quality under smallholder maize systems in the region. Soil samples were collected from two land use practices: agroforestry adoption (90) and non-agroforestry adoption (30) at 0-30 cm depth from two locations (Busia and Kakamega counties). Results showed variations in soil characteristics between the study locations. Soils in Kakamega contained higher concentrations of soil organic carbon (SOC), exchangeable cations, and micronutrients. On average, agroforestry adoption significantly (P ≤ 0.05) improved soil physicochemical properties. Under agroforestry adoption, bulk density (BD) reduced by 21% (from 1.4 to1.1 g cm-3), while (SOC) increased by 75% (0.8-1.4%), P by 80% (3.0-5.4 mg kg-1), exchangeable K by 256% (0.3-8.0 cmol kg-1), Ca by 100% (1.0-2.0 cmol kg-1), S by 50% (0.2-0.3 mg kg-1), and Cu by 18% (2.8-3.3 mg kg-1). Agroforestry adoption significantly increased K and Cu levels above the critical thresholds of 0.4 cmol kg-1 and 1.0 mg kg-1, respectively, at both locations. Sesbania sesban and Leucaena leucocephala influenced soil BD, pH and P (4.3.-7.0 mg kg -1), exchangeable K (0.4-0.7 cmol kg-1), Mg (0.1-0.2 cmol kg-1), and Mn (13.5-25.2 mg kg-1) at both locations, while Calliandra calothyrsus significantly increased SOC in Kakamega only. These findings highlight the significance of agroforestry in soil fertility management. Furthermore, Sesbania proved to be effective in enhancing the characteristics of soils at both sites, hence, the need for its inclusion in agroforestry extension messages. Further studies are needed to understand nutrient release mechanisms from agroforestry biomass and their influence on soil characteristics and maize yield in smallholder farming systems.
农林业是一种可持续的土地利用方式，20世纪90年代初在肯尼亚西部被引入，作为一种土壤肥力补充策略。从那时起，这种做法对土壤质量的影响鲜有证据。开展了一项研究，以评估该地区小农玉米种植系统中采用农林业对土壤质量的影响。在两个地点（布西亚县和卡卡梅加县）0至30厘米深度处，从两种土地利用方式中采集土壤样本：采用农林业的（90个）和未采用农林业的（30个）。结果表明，研究地点之间的土壤特性存在差异。卡卡梅加的土壤含有较高浓度的土壤有机碳（SOC）、交换性阳离子和微量营养素。平均而言，采用农林业显著（P≤0.05）改善了土壤理化性质。在采用农林业的情况下，容重（BD）降低了21%（从1.4降至1.1克/立方厘米），而（SOC）增加了75%（0.8-1.4%），磷增加了80%（3.0-5.4毫克/千克），交换性钾增加了256%（0.3-8.0厘摩尔/千克），钙增加了100%（1.0-2.0厘摩尔/千克），硫增加了50%（0.2-0.3毫克/千克），铜增加了18%（2.8-3.3毫克/千克）。在两个地点，采用农林业均显著提高了钾和铜的含量，分别高于临界阈值0.4厘摩尔/千克和1.0毫克/千克。田菁和银合欢对两个地点的土壤BD、pH值和磷（4.3-7.0毫克/千克）、交换性钾（0.4-0.7厘摩尔/千克）、镁（0.1-0.2厘摩尔/千克）和锰（13.5-25.2毫克/千克）有影响，而红千层仅显著增加了卡卡梅加的SOC。这些发现突出了农林业在土壤肥力管理中的重要性。此外，田菁被证明在改善两个地点的土壤特性方面有效，因此，有必要将其纳入农林业推广信息中。需要进一步研究，以了解农林业生物量的养分释放机制及其对小农种植系统中土壤特性和玉米产量的影响。
