Eyes in the Sky, Boots on the Ground: Assessing Satellite‐ and Ground‐Based Approaches to Crop Yield Measurement and Analysis
利用乌干达东部数百个小农地块的玉米数据，比较了农户报告、子地块作物切割、全地块收获和卫星遥感四种产量测量方法，发现卫星方法在解释全地块收获产量变异方面表现不逊于甚至优于传统地面方法，且对投入产出关系的估计与作物切割法相似。
Understanding the determinants of agricultural productivity requires accurate measurement of crop output and yield. In smallholder production systems across low‐ and middle‐income countries, crop yields have traditionally been assessed based on farmer‐reported production and land areas in household/farm surveys, occasionally by objective crop cuts for a sub‐section of a farmer's plot, and rarely using full‐plot harvests. In parallel, satellite data continue to improve in terms of spatial, temporal, and spectral resolution needed to discern performance on smallholder plots. This study evaluates ground‐ and satellite‐based approaches to estimating crop yields and yield responsiveness to inputs, using data on maize from Eastern Uganda. Using unique, simultaneous ground data on yields based on farmer reporting, sub‐plot crop cutting, and full‐plot harvests across hundreds of smallholder plots, we document large discrepancies among the ground‐based measures, particularly among yields based on farmer‐reporting versus sub‐plot or full‐plot crop cutting. Compared to yield measures based on either farmer‐reporting or sub‐plot crop cutting, satellite‐based yield measures explain as much or more variation in yields based on (gold‐standard) full‐plot crop cuts. Further, estimates of the association between maize yield and various production factors (e.g., fertilizer, soil quality) are similar across crop cut‐ and satellite‐based yield measures, with the use of the latter at times leading to more significant results due to larger sample sizes. Overall, the results suggest a substantial role for satellite‐based yield estimation in measuring and understanding agricultural productivity in the developing world.