Maintaining nitrogen level is key to healthy sweet potato crops

Carefully managing nitrogen levels is the most important trick to obtain high yields from sweet potato crops. Too little nitrogen and the plants do not grow properly and too much of it, again, leads to low yield.

A recent study focuses on how much nitrogen is needed to maximize yields of sweet potato crops. The researchers discovered that field history matters when trying to apply the optimal amount of nitrogen for sweet potato crops. Cover crops grown in the same plots prior to sweet potato crops affected how much nitrogen was needed. Cover crops are often grown cyclically with economic or cash crops. They may be incorporated into the soil as green manure.

Sweet potato plants, grown in plots previously used to grow legume cover crops, needed 35% less nitrogen fertilizer. Growing sweet potatoes after a cereal cover crop, however, was no different than growing them in a plot that previously only had weeds.

Different cover crops bring different benefits to the growth of crops. Legumes, for example, can increase soil nitrogen levels. Beneficial bacteria in their root nodules pull atmospheric nitrogen into the soil. However, they also decompose faster than cereal cover crops once terminated.

Currently, recommendations of how much nitrogen fertilizer to use with sweet potato crops do not consider the history of cultivation in the area. That can result in farmers using more or less fertilizer than needed.

Adalton Fernandes, an agronomist at the Center for Tropical Roots and Starches at Sao Paulo State University in Brazil said, " We now better understand how much nitrogen is needed to maximize sweet potato yields in tropical regions. This will help manage the application of mineral nitrogen fertilizers during sweet potato cultivation." In addition to maximizing yields, using less fertilizer also reduces costs for farmers.

The study appears in Agronomy Journal.