Jesse and Meghan wanted to understand the contribution of spring legume cover crops
towards the nitrogen requirements of the following cash crop. They established a randomized
block design with low- and high-legume cover crop treatments. They sampled cover crop
biomass and used lab analyzes paired with a free online calculator from Oregon State
University to estimate plant available nitrogen (PAN) from the cover crops, and also tested
an in-field method to estimate PAN. Finally, they took soil nitrate samples throughout the
growing season to better understand the best tools to manage his fertility.

In a Nutshell

• Legume cover crop mixes can supply a lot of PAN, potentially in excess of the needs of some vegetable crops.
• Cover crops act as an effective catch crop by reducing soil nitrate early in the season.
• Legume content in a cover crop mix moderates in-season PAN as indicated by soil nitrate.
• Cover crop biomass sampling coupled with lab analysis and the online calculator provided a simple, cost effective tool for quantifying PAN contribution of cover crops.
• Both pre-plant and mid-season soil nitrate-nitrogen sampling were effective tools for predicting PAN availability when Jesse and Meghan compared their results to the literature.