Over the last year and a half, EPAR has constructed over 150 indicators related to agricultural development, and shared our decisions on data cleaning and indicator construction. We do this work and share our outputs both to facilitate analyses of these rich datasets and to make estimates of relevant indicators available to a broader audience of potential users. There are numerous decision points in the process of constructing indicators that affect the final estimates. These choices and the resulting estimates can inform policy and decision making both in-country and among international development stakeholders. This post is part of a blog series examining the potential consequences of different measurement choices. In the first post of this series, we discussed how the choice of area measure (area planted vs. area harvested) affects estimates of land productivity. In this post, we examine the implications of using different area measurements of multi-cropped plots when estimating crop yield.

Planting multiple crops on a single plot of land can diversify the risk of any single crop’s susceptibility to climate, pest or disease shocks, and unpredictable price movements. Additionally, intercropping multiple crops, particularly nitrogen fixing legumes, has been found to have productivity benefits. For these reasons, farmers commonly plant multiple crops together. The household-level survey data from the World Bank’s Living Standards Measurement Study - Integrated Surveys on Agriculture (LSMS-ISA) Tanzania National Panel Survey (TNPS) finds that in the 2013-2014 long rainy season in Tanzania, 64% of cultivated plots contain more than one crop. Given the prevalence of multi-cropped plots, measurement choices surrounding these plots could have large implications for interpreting productivity.

In a review of 40 papers found in top journals over the past five years examining crop yield in low-income settings, none described any adjustments to the production estimates or crop areas to account for intercropping. Three of the 40 papers indicated the entire plot size was used in the denominator for yield, effectively ignoring the production of intercrops in making yield calculations for any given crop. The area used in the yield analysis in the remaining 37 papers was not specified.

To determine if these area choices have an effect on yield estimates, we used four different methods of dealing with intercropped plots. Figure 1 shows a typical 1-hectare plot, with a quarter solely planted with maize and the remaining three-quarters intercropped with sorghum and beans.

  • Method 1: the entire plot is considered the area under each crop
  • Method 2: the estimated proportion of the plot cultivated with a given crop (e.g. ¼) is considered the area under that crop, even when it shares the space with other crops
  • Method 3: the entire plot area is simply divided by the number of crops
  • Method 4: areas are estimated based on the proportion of the plot cultivated with seasonal crops, adjusted by the number of fruit trees/permanent crops and a set of per-plant (per-tree) area estimates.


Figure 1. Example of area calculation methods in the presence of multiple crops (1 ha plot)

Using the household level data from the World Bank’s Living Standards Measurement Study - Integrated Surveys on Agriculture (LSMS-ISA) for Tanzania, EPAR tested how different methods for measuring multi-crop plot area affects mean yield estimates for maize and rice, with results shown in Table 1. Particularly for maize, using methods 3 and 4, which accounts for space taken by other crops, produces much higher average yields than methods 1 and 2.

Using these different methods to construct yield estimates, we next ran a set of linear regressions with the different estimated yields as the dependent variable, controlling for inputs such as seed, fertilizer, labor etc., management choices such as intercropping, and plot characteristics such as soil quality and the gender of plot manager. We find that when using methods 1 and 2 (which are unadjusted for intercropping), intercropping is negatively correlated with maize yield. Using methods 3 and 4, however, which do account for the presence of multiple crops on the same plot, intercropping is positively associated with yield. Not only is the interpretation of the relationship between yield and inter-cropping reversed according to the area method chosen, but benefits associated with farm management strategies such as intercropping can be masked.

By Isabella Sun

Summarizing research by Ayala Wineman, C. Leigh Anderson, Travis Reynolds, & Pierre Biscay