Norwegian University of Life Science, Faculty of Environmental Science and Natural Resource Management, P.O. Box 5003, No1432, Aas, Norway; Hawassa University, Wondo Genet College of Forestry and Natural Resource, P.O. Box, 128, Shashemene, Ethiopia.
International Crops Research Institute for the Semi-Arid Tropics, P.O. Box, 5689, Addis Ababa, Ethiopia.
J Environ Manage. 2021 Oct 15;296:113187. doi: 10.1016/j.jenvman.2021.113187. Epub 2021 Jul 1.
On the cultivated slopes of the highlands of southwest Ethiopia, soil degradation due to water erosion is a challenge for crop production. To limit surface runoff and soil erosion, soil bunds often in combination with trenches, constructed along contour lines, are common. In addition to the interception of surface runoff, soil bunds may affect crop yield. Here, we evaluate effect of soil bunds on surface runoff and maize yield, using FAO's AquaCrop model, calibrated based on field experiments in the Bokole-Karetha watershed, in SW Ethiopia. Experiments were conducted in 2018 and 2019 on three neighboring fields, each comprising plots in triplicate without and with soil bunds. Experimental data from 2018 to 2019, which were average and above average with respect to rainfall, indicate that water availability was sufficient or even in excess for maize production. Soil bunds significantly (p < 0.05) reduced surface runoff, but maize yield did not differ significantly. In plots without soil bunds, the AquaCrop model described surface runoff satisfactorily after slight adjustment of the curve number (related to infiltration capacity) in one of the three fields. Maize yields were reproduced adequately after calibrating soil fertility and adjusting water productivity. After calibration and validation, the AquaCrop model was used to hindcast surface runoff and grain yield from 1999 to 2017, given available climatic data for the region. Hindcasts show that maize yield in the Bokole-Karetha watershed, with its relatively high rainfall, is not significantly affected by rainfall in two of the three fields. In the third field maize yield decreases slightly, but significantly (p < 0.05) with rainfall. In the short run, yield differences between plots with and without soil bunds are not significant. However, eventually high surface runoff from plots without soil bunds are expected to result in unsustainable crop production, due to significant erosion and degradation of the often nutrient-poor soils. Implementation of soil and water management techniques, combined with fertilization, are important to prevent soil degradation and nutrient stress on sloping land.
在埃塞俄比亚西南部高原的耕地坡地上，水蚀导致的土壤退化是作物生产的一个挑战。为了限制地表径流和土壤侵蚀，通常沿着等高线建造的土埂与沟渠相结合。除了拦截地表径流外，土埂还可能影响作物产量。在这里，我们使用 FAO 的 AquaCrop 模型来评估土埂对地表径流和玉米产量的影响，该模型是基于埃塞俄比亚西南部 Bokole-Karetha 流域的田间试验进行校准的。试验于 2018 年和 2019 年在三个相邻的地块上进行，每个地块都包含三个重复的无土埂和有土埂的小区。2018 年至 2019 年的实验数据表明，降雨平均且高于平均水平，表明水分供应对玉米生产是充足的，甚至是过剩的。土埂显著（p<0.05）减少了地表径流，但玉米产量没有显著差异。在没有土埂的小区中，AquaCrop 模型在三个地块中的一个地块稍微调整了曲线数（与入渗能力有关）后，对地表径流的描述令人满意。在校准土壤肥力并调整水分生产力后，玉米产量得到了充分的再现。经过校准和验证后，使用 AquaCrop 模型根据该地区可用的气候数据，对 1999 年至 2017 年的地表径流和谷物产量进行了回溯预测。回溯预测表明，在 Bokole-Karetha 流域，相对较高的降雨量并没有显著影响三个地块中的两个地块的玉米产量。在第三个地块中，玉米产量略有下降，但与降雨显著相关（p<0.05）。在短期内，有土埂和无土埂小区之间的产量差异并不显著。然而，最终由于缺乏养分的土壤的严重侵蚀和退化，无土埂小区的高地表径流量预计将导致不可持续的作物生产。因此，实施水土管理技术，结合施肥，对于防止坡地土壤退化和养分胁迫非常重要。
