How Do You Fertilize Onions Under Plastic Mulch?
Plastic mulch encourages healthy microbes to grow in the soil. It helps maintain soil temperatures and moisture levels. Carbon dioxide builds up under the mulch, escaping through the holes around the plants, which encourages more vegetable growth. Onions have shown they benefit greatly from plastic mulch and they benefit from fertilizing the soils under the mulch. Prepare your vegetable garden for planting four weeks before the last average spring frost. Dig a trench four inches deep and 10 feet long with a spade. Spread half a cup of fertilizer with 10 percent nitrogen, 20 percent phosphorus and 10 percent potassium ratio to the bottom of the trench in a band. Cover the fertilizer with two inches of soil. Transplant your onion plants every four inches along the trench. Lay down a drip irrigation system with one drip tube watering each plant. Spread the plastic mulch in a sheet over the row of onions. Cut holes in the plastic with a knife over each onion and allow the plant above the g
