Improving fertilizer use efficiency has remained a challenge, particularly for small-scale farming in undulating ‘abnormal’ landscapes of East Africa. Milne's 1930s concept on ‘Catena’ was considered as a breakthrough in understanding soil variability and its implication on productivity in East African highlands. However, there is limited information on how the ‘Catena’ features could be used for fine tuning fertilizer recommendations. We initiated multiple on-farm replicated experiments in three wheat-growing districts (Endamohoni, Lemo and Worreilu) in the Ethiopian highlands in 2014, 2015 and 2016 to assess landscape positions affecting crop-nutrient responses, identify yield limiting nutrients across the ‘Catena’ (N, P, K, S and Zn) and quantify effects of landscape positions on resources use efficiency. We clustered farmlands across the ‘Catena’ (Hillslopes, Midslopes and Footslopes) based on land scape positions in the respective locations. Wheat yield was more strongly and significantly affected by landscape positions (P < 0.001) than by nutrient sources or rates. The crop response to fertilizers was 50 to 300% higher in foot slopes than in hillslopes, depending on locations and inputs levels. With increasing slope, there was a decrease in a crop fertilizer response due to a significant decrease in soil organic carbon, clay content and soil water content, with r2 of 0.95, 0.86 and 0.96, respectively. The difference in the crop response between landscape positions was significantly higher (P < 0.05) with higher rates of nutrient applications (>N92 P46) while differences between landscape positions diminish at lower rates. Yield benefits due to application of K was significant only in the dry years (P < 0.05), while there was hardly any yield benefit from the application of zinc and sulfur. The crop nitrogen recovery fraction and crop water productivity decreased with an increasing slope regardless of nutrient combinations. The results indicated that the landscape position could be considered as a proxy indicator for targeted fertilizer application, particularly in farms with undulating topographic features. Hillslopes are better served by the application of organic fertilizers along with conservation measures as applying higher rates of mineral fertilizer in hillslopes would rather increase the risk of downstream nutrient movement.

中文翻译：

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景观位置决定了东非高地小麦耕作系统中作物肥料的反应

提高肥料使用效率仍然是一个挑战，特别是对于东非起伏的“异常”景观中的小规模农业而言。Milne 1930 年代关于“Catena”的概念被认为是理解土壤变异性及其对东非高地生产力的影响的一个突破。但是，关于“Catena”功能如何用于微调肥料建议的信息有限。我们于 2014 年、2015 年和 2016 年在埃塞俄比亚高地的三个小麦种植区（Endamohoni、Lemo 和 Worreilu）启动了多项农场重复实验，以评估影响作物养分反应的景观位置，确定“Catena”中限制产量的养分（N、P、K、S 和 Zn）并量化景观位置对资源利用效率的影响。我们根据各自位置的景观位置将农田聚集在“Catena”（Hillslopes、Midslopes 和 Footslopes）上。小麦产量受景观位置的影响更大且显着（磷< 0.001) 比营养来源或比率。根据地点和投入水平，山坡上的作物对肥料的反应比在山坡上高 50% 到 300%。随着坡度的增加，由于土壤有机碳、粘土含量和土壤水分含量显着降低，作物对肥料的响应降低，r2分别为 0.95、0.86 和 0.96。景观位置之间作物响应的差异显着更高（磷< 0.05)，养分施用率较高 (>N92 P46)，而景观位置之间的差异以较低的速率减少。仅在干旱年份，施钾带来的产量效益显着（磷< 0.05)，而锌和硫的应用几乎没有任何产量收益。无论养分组合如何，作物氮回收率和作物水分生产力都随着斜率的增加而下降。结果表明，景观位置可以被视为目标施肥的代理指标，特别是在具有起伏地形特征的农场中。施用有机肥料和保护措施可以更好地服务于山坡，因为在山坡上施用更高比例的矿物肥料会增加下游养分移动的风险。