Polyculture chemicals into the environment such as eutrophication of fresh water or the presence of excess atmospheric nitrogen are greatly reduced in polycultures. Other negative impacts of modern agriculture are similarly reduced. Excessive tillage occurs in most modern agricultural practices, but removes essential microbes and nutrients from the soil that are conserved in polycultures, especially permacultures. Agricultural machinery not only uses fossil fuels and creates waste, but is more costly to farmers. Because polyculture relies on natural systems of crop maintenance these costs can be eliminated as well. Modern agriculture is also dependent on a very limited number of plant species.
Epigenetics of plant growth and development premise in plants. In hybrids, lack of proper regulatory action, such as silencing by methylation, leads to uninhibited genes. If the gene is involved in growth, such as photosynthesis, the plant will experience increased vitality (Ni et al. 2008). The results heterosis can be seen in traits such as increased fruit yield, earlier ripening, and heat tolerance. Heterosis has been shown to provide increased general growth and fruit yield in tomato plants (Xiaodong). Epigenetics of plant growth and development Plants depend on epigenetic processes for proper function. Epigenetics has been defined as "the study of changes in gene function that