Can I grow wheat or other crops between poplar rows and what spacing allows it?

Yes, poplar is one of the best trees for intercropping because it sheds leaves in winter, letting in light for the rabi crop. A common layout is paired or block planting with wide spacing, for example rows about 5 metres apart with trees 4 metres within the row, or boundary and bund planting, so machinery and crops fit between. Wheat, sugarcane, fodder, turmeric and vegetables are grown between young poplar. As the trees grow taller and the canopy increases, shade rises in later years and yields of the intercrop drop, especially close to the trunks, so the best intercrop returns come in the early to middle years. Keep the trees pruned, manage water, and choose intercrops suited to your soil. Plan the layout before planting so the spacing matches your machinery and crop.