Sustainable Intensification (SI) is essential for Sub-Saharan Africa (SSA) to meet the food demand of the growing population under conditions of increasing land scarcity. However, access to artificial fertilizers is limited, and the current extension system is not effective in serving smallholder farmers. This paper studies farmers' response to improved fertilizer availability under field conditions. Data on farms and families were collected from 267 smallholder farms, while data on fertilizer use and crop response to fertilizer were collected on 127 farm plots. Fertilizer applications and maize yields were measured, and benefit to cost ratio (BCR) of fertilizer application was calculated and to assess its effect on food security. Farm household typologies were used to determine differences in farm endowment and food security classes. Fertilizer application did not significantly improve maize yields in 2017 due to unfavorable weather conditions and pest infestations, whereas significant yield responses were observed in 2018. Consequently, fertilizer application was economically beneficial (BCR >1) for only 45% of the farmers in 2017, compared to 94% in 2018 when 80% of the farmers passed the technology adaptation point (BCR > 2). Surprisingly, economic returns did not vary significantly between household types, implying that fertilizer application provides comparable benefits across all farm types. This is partly explained by the fact that soil fertility varied little between farm types (soil carbon content, for example, showed no correlation with farmer endowment). Still, large differences were observed in farmers' willingness to invest in larger fertilizer applications. Only a small proportion of farmers is expected to increase fertilizer applications as recommended. Our work demonstrates the need to address risks for smallholders and shows that socio-economic aspects are more important than biophysical constraints for policies promoting sustainable intensification.

中文翻译：

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肯尼亚西部的可持续集约化：谁将受益？

可持续集约化（SI）对于撒哈拉以南非洲（SSA）在土地日益稀缺的情况下满足不断增长的人口的粮食需求至关重要。然而，获得人工肥料的机会有限，目前的推广系统无法有效地为小农服务。本文研究了农民在田间条件下对提高肥料可用性的反应。农场和家庭的数据是从 267 个小农场收集的，而肥料使用和作物对肥料的反应数据是在 127 个农田收集的。测量了施肥量和玉米产量，计算施肥的成本效益比 (BCR) 并评估其对粮食安全的影响。农场家庭类型被用来确定农场禀赋和粮食安全等级的差异。由于不利的天气条件和虫害，施肥在 2017 年没有显着提高玉米产量，而在 2018 年观察到显着的产量反应。 因此，2017 年施肥对只有 45% 的农民具有经济效益（BCR >1），相比之下，2018 年有 94%，当时 80% 的农民通过了技术适应点（BCR > 2）。令人惊讶的是，家庭类型之间的经济回报并没有显着差异，这意味着施肥在所有农场类型中都提供了可比的收益。部分原因是不同农场类型的土壤肥力变化很小（例如，土壤碳含量与农民禀赋没有相关性）。尽管如此，在农民方面观察到了很大的差异 愿意投资于更大的肥料应用。预计只有一小部分农民会按照建议增加施肥量。我们的工作表明需要解决小农的风险，并表明社会经济方面比促进可持续集约化政策的生物物理限制更重要。