Damiba Wendyam Arsene Flavien, Gathenya John Mwangi, Raude James Messo, Home Patrick Gathogo
Civil Engineering Department (Environment, Arid and Semi-Arid Lands (ASAL)), Pan African University-Institute for Basic Sciences Technology and Innovation (PAUSTI), Jomo Kenyatta University of Agriculture and Technology (JKUAT), P.O. Box 62000-00200, Nairobi, Kenya.
Soil, Water and Environmental Engineering Department, Jomo Kenyatta University of Agriculture and Technology (JKUAT), P.O. Box 62000-00200, Nairobi, Kenya.
Heliyon. 2024 Feb 5;10(5):e25611. doi: 10.1016/j.heliyon.2024.e25611. eCollection 2024 Mar 15.
Land and water degradation caused by soil erosion and climate change pose major environmental threats, particularly in agricultural watersheds. Soil erosion in a catchment leads to low crop yields due to declining soil quality (SQ), productivity and sustainability. However, very few studies have been done to assess soil health in Kenya, and none in Narok County. Thus, the aim of this study was to evaluate the soil sustainability status in Kakia-Esamburmbur catchment, based on the identification of key indicators (IKI) from a large dataset (LDS) of 23 indicators, across three land use types designated as grass land (GL), crop land (CL) and forest land (FL). To achieve the stated objective, two soil quality indexing methods were employed: the Additive Soil Quality Index (A-SQI) using the LDS; and the Weighted Soil Quality Index (W-SQI) using Principal Component Analysis (PCA) as a reduction tool to obtain the IKI set. The results show that at a depth of 20 cm, the catchment's soils characteristics did not differ significantly. The two methods (A-SQI and W-SQI) resulted in FL having the highest SQI mean values (0.61, 0.57), followed by CL (0.59, 0.55), while the lowest SQI mean value was recorded in GL (0.58, 0.53). Additionally, the sensitivity analysis showed W-SQI as the most sensitive and superior method in the evaluation of SQI changes due to its high sensitivity and coefficient of variation (CV), at 2.25 and >12 %, respectively. Among the ten IKI, CEC made the greatest contribution to SQ (18.68 %), followed by BD (15.61 %), BIR (14.71 %), Mg (14.26 %), MBN (8.30 %), MBC (8.26 %), Sand (6.77 %), Moisture (5.75 %), TOC (5.16 %), and PMN (2.63 %). The findings show that the catchment belongs to the "medium" category of SQ. The IKI can help save time and reduce the cost of intensive lab works for temporal assessment and monitoring of the effects of different land use on SQ.
土壤侵蚀和气候变化导致的土地与水体退化构成了重大环境威胁，在农业流域尤其如此。集水区的土壤侵蚀会因土壤质量（SQ）、生产力和可持续性下降而导致作物产量降低。然而，肯尼亚评估土壤健康的研究极少，纳罗克县尚无此类研究。因此，本研究的目的是基于从23项指标的大型数据集（LDS）中识别关键指标（IKI），评估卡卡亚 - 埃桑布尔姆布尔集水区的土壤可持续性状况，该数据集涵盖三种指定的土地利用类型，即草地（GL）、耕地（CL）和林地（FL）。为实现既定目标，采用了两种土壤质量指数方法：使用LDS的加法土壤质量指数（A - SQI）；以及使用主成分分析（PCA）作为降维工具来获取IKI集的加权土壤质量指数（W - SQI）。结果表明，在20厘米深度处，集水区的土壤特性无显著差异。两种方法（A - SQI和W - SQI）得出的结果是，林地的SQ平均值最高（0.61, 0.57），其次是耕地（0.59, 0.55），而草地的SQ平均值最低（0.58, 0.53）。此外，敏感性分析表明，W - SQI在评估SQ变化方面是最敏感且更优的方法，因为其敏感性和变异系数（CV）分别高达2.25和>12%。在十个IKI中，阳离子交换量（CEC）对土壤质量的贡献最大（18.68%），其次是容重（BD，15.61%）、生物可利用性指数（BIR，14.71%）、镁（Mg，14.26%）·、微生物生物量氮（MBN，8.30%）、微生物生物量碳（MBC，8.26%）、砂粒（Sand，6.77%）、水分（Moisture，5.75%）、总有机碳（TOC，5.16%）和潜在矿化氮（PMN，2.63%）。研究结果表明，该集水区属于土壤质量的“中等”类别。IKI有助于节省时间并降低密集实验室工作的成本，用于不同土地利用对土壤质量影响的时间评估和监测。
