The main feeds for hogs are corn, barley, oats and wheat for energy and soybean meal for protein. Crop rotation is good land management because it enhances the soil structure, avoids nutrient depletion, substantially reduces soil erosion and aids in water retention. Crop residues such as stalks and leaves are left standing in fields over the winter, to reduce wind and water erosion. Clover and other green legumes are ploughed into the soil to improve fertility and increase organic matter, preventing soil compaction. Some crops are now planted directly in unworked land, without tillage, reducing both soil erosion and fuel consumption.
Farmers fertilize the soil with manure.
As gardeners know, manure from farm animals provides important natural fertilizers and soil conditioners. In Canada, there is an abundant land base to utilize manure without negative environmental effects. However, when manure is not managed properly, it can become an environmental problem by way of run-off into rivers and contamination of ground water through leaching. Pork producers and government are working closely and continually to solve these problems. Research on ways to optimize and find alternative uses of manure are ongoing.