Does Cover Crop Biomass Impact Nitrate Loss Reduction?

To find the right combination of seeding method and date for cover crops for his operation, a farmer in southeast Iowa set up his own demonstration comparing three methods on four dates with 1-2 bushels of rye per acre. He recently shared photos of the cover crops taken April 12-13.

It is clear that the earlier seeded cover crops resulted in significantly more biomass than the November seeding date and that left him wondering if nitrate loss reduction is related to biomass production and if the less expensive method of broadcasting with fertilizer generated enough growth to have an impact on nitrate.

As it turns out, there has been some recent analysis shows nitrate reduction is correlated with cover crop biomass. More biomass – more nitrate reduction. More biomass can also provide weed suppression benefits, especially of early season annuals.

If utilizing a later seeding it is important to consider how long it will grow in the spring. If the cover crop is being used before corn and killed early (10-14 days before planting), there will be limited benefits. However, ahead of soybean there is additional spring growing days that can allow significant growth before that cover crop is terminated, about 7 days before planting for new cover crop users or after planting for more experienced cover crop users.

If you have photos you want to share or questions, email those to and we’ll get them up in our future postings.

-Liz Ripley