This post is written by Jongwoo, K., Mason, N.M and Snapp, S., Michigan State University

In many developing countries, including Tanzania, food insecurity and child malnutrition remain persistent problems. In 2017, globally, about 151 million children under age five are stunted, where 55 percent and 39 percent of these children live in Asia and Africa, respectively; but Africa has shown relatively slow progress in reducing stunting and it is the only region where the rate of stunting has risen since 2000. Malnutrition is a leading cause of child mortality, making children more vulnerable to severe diseases. Approximately 45 percent of global deaths of children under age five are linked to malnutrition, and the mortality rate of children in sub-Saharan Africa (SSA) is the highest in the world. Tanzania — a focal country in this study — is the third worst affected country in SSA based on the prevalence of stunting.

Agriculture and nutrition are closely linked because the majority of undernourished people still live in rural areas and many of them are smallholder farmers. This linkage suggests that agricultural intensification via farmers’ adoption of improved inputs and management practices may improve the nutritional status of nutritionally vulnerable household members including young children. This can be done by enhancing the household’s agricultural production, productivity, and/or income, as well as by providing better access to more diverse or nutritious foods. However, there is an emerging consensus that conventional agricultural intensification via high-yielding crop varieties and inorganic fertilizers may be insufficient to sustainably raise agricultural productivity and could have negative environmental consequences (Pingali, 2012). Moreover, in many parts of SSA, rapidly growing populations and a lack of new land to farm has led to continuous cultivation of plots and reduced fallowing, thereby degrading soils and adversely affecting crop yields and yield response to inorganic fertilizers. A major question then is, what is the impact of this declining natural resource base on family nutrition status, and should agricultural development just focus on intensification (via fertilizer subsidies), or pay equal attention to organic matter technologies and agrobiodiversity for a sustainable approach to intensification?

In this context, agricultural sustainable intensification (SI) is, at its core, an approach that seeks to “produce more food from the same area of land while reducing the environmental impacts” (Godfray et al., 2010, p. 813). In our study, we focused on the effects of SI maize production on child nutrition outcomes in maize-growing households in Tanzania. We focused on maize due to its importance as a staple food in Tanzania, and because it accounts for approximately 75 percent of the total cropped area in the country. To do this, we applied a multinomial endogenous treatment effects (METE) model, combined with the correlated random effects (CRE) approach, using three waves of nationally representative household panel survey data (the Tanzania National Panel Surveys of 2008/09, 2010/11, and 2012/13). These surveys were conducted by the TNBS in conjunction with the World Bank.

Some of our key findings included the results from our exploration of the effects of different combinations of three soil-fertility management practices (inorganic fertilizer, organic fertilizer, and maize-legume intercropping) used by rural Tanzanian households on their maize plots on the nutritional outcomes of children aged 6-59 months within the household. The results suggested that joint use of inorganic fertilizer with maize-legume intercropping and/or organic fertilizer (which we refer to as the sustainable intensification or SI group of practices) is associated with increases in children’s height-for-age z-score (HAZ) and weight-for-age z-score (WAZ), as compared to households that adopt none of these practices. The positive effects of the SI group are mainly among children aged 25-59 months who, as compared to younger children, are less likely to be breastfed and may be more directly affected by household diet changes associated with changes in agricultural practices. The joint use of maize-legume intercropping and inorganic fertilizer is a key driver of the positive SI effects, in the form of crop income and productivity pathways.