In many countries in sub-Saharan Africa, low crop yield response to inorganic fertilizer contributes to low profitability of fertilizer use and reduces the positive effects of and returns to input subsidy programs (ISPs). A major reason for poor crop yield response to fertilizer is low soil quality. However, using other soil fertility management (SFM) practices in conjunction with fertilizer can improve its response rate. But do ISPs encourage (‘crowd in’) or discourage (‘crowd out’) the use of such SFM practices? Using nationally representative household panel survey data, we estimate the effects of subsidized fertilizer acquired through Zambia’s ISP on the use of several SFM practices: (i) leaving land fallow, (ii) intercropping, and (iii) applying animal manure. For each practice, we estimate the household-level effects of an increase in the quantity of subsidized fertilizer acquired on the probability of SFM adoption, land area covered by SFM, and the share of land dedicated to SFM, using the ordinary least squares, fixed effects, and fixed effects-instrumental variable estimators. The results suggest that subsidized fertilizer has statistically significant crowding out effects on all fallow variables, for all measures of adoption, using all estimators. Additionally, we find some evidence that subsidized fertilizer crowds out intercropping. However, the weight of the evidence suggests that subsidized fertilizer has no significant effect on intercropping with legumes or the use of animal manure. By disincentivizing fallowing and intercropping, Zambia’s ISP may be inadvertently reducing soil quality and the effectiveness and profitability of its main input, inorganic fertilizer.

在撒哈拉以南非洲的许多国家，无机肥料对作物产量的低反应导致肥料使用的低盈利能力，降低了投入补贴计划(ISPs)的积极效应和回报。土壤质量差是造成作物产量差的主要原因。但是，结合肥料使用其他土壤肥力管理(SFM)措施可以提高其响应率。但是isp是鼓励(“挤进来”)还是不鼓励(“挤出去”)使用这类SFM做法呢?利用具有全国代表性的家庭面板调查数据，我们估计了通过赞比亚ISP获得的补贴肥料对几种SFM做法的影响:(i)留出土地休耕，(ii)间作，(iii)施用动物粪便。对于每一个练习,我们估计的实施减贫效应增加肥料获得补贴的数量在SFM采用的概率,SFM覆盖的土地面积,土地致力于SFM和分享,使用普通最小二乘法,固定效果,和固定effects-instrumental变量估计。结果表明，对于采用的所有措施，使用所有的估计量，补贴化肥对所有休耕变量都有统计学上显著的挤出效应。此外，我们还发现一些证据表明，补贴化肥会抑制间作。然而，证据的分量表明，补贴化肥对豆类间作或动物粪便的使用没有显著影响。通过抑制休耕和间作，赞比亚的ISP可能在无意中降低了土壤质量以及其主要投入，即无机肥料的有效性和盈利能力。