Can small-scale backyard gardening produce more food per acre than broadscale [grain] farming?
Efficacy of food production per square foot/acre differs from soil quality and rate of regeneration. It's also a case of if you can produce year round. Some permaculture specialists, monitored one case in an article of &quot;Green America&quot; A 500 sq foot garden producing 300 lbs of produce per year. Among other's. Soil nutrient recycling is a key aspect of producing food year round, along with temperature (Green houses).

Composting
Soil/air temp
Growth rate of produce involved
So the answer is &quot;Yes&quot; if dedication is involved.