Soil fertility in maize farming areas can decline due to lack of soil improvement. Researchers studied using hairy vetch with maize to boost soil fertility. They found that sunnhemp produced the most biomass and fixed the most nitrogen, followed by cowpea and then hairy vetch. Sunnhemp also improved maize yields significantly when intercropped. Hairy vetch, cowpea, and sunnhemp released more nitrogen when their residues decomposed compared to maize residues alone. Soil acidity did not affect hairy vetch growth significantly.