2. African crop yield - If US can grow 159 bushels One factor (apart from soil type/access and amounts of water/available tech) might also be this: maybe Gates

2. African crop yield - If US can grow 159 bushels One factor (apart from soil type/access and amounts of water/available tech) might also be this: maybe Gates is considering the environmental impact of growing those 159 bushels just isn't worth it. Without the heavy use of pesticides, fertilizers etc the yield would be lower, but the impact on nature would be much more reasonable and sustainable.