We’ve planted field peas on all of our dryland fields several times in our winter wheat-corn-field pea crop rotation.

We’ve learned quite a bit over this time on growing field peas and what to expect and watch for as this rotation continues over time, and I thought I’d share some of what we have learned and a few things to watch for in field pea production.

I had several calls one year on how we approach fertilizing winter wheat following our field pea crop. Field peas are a legume that produces nitrogen (N) during their growth cycle. I’ve been told field peas will produce a pound to a pound and a half of nitrogen for every bushel of field peas they produce per acre.

A 30-bushel-per-acre field pea crop could be expected to produce from 30-45 pounds of N per acre. Field peas are one of the best N producers in the legume family. I’ve also been told that this N takes up to 18 months to break down into a plant-useable form of N.

Even though field peas produce a lot of N during their growth cycle I also realize the harvesting of the grain from the field peas is removing a lot of N from the field. I’m hesitant to give the field peas too much N credit for winter wheat since we’re removing a lot of the N they produced with the grain we remove from the field.

When it comes to fertilizing our winter wheat we soil sample each field in the spring to determine the N requirements for yield goals. We apply 10 pounds of N with our starter mix when we seed winter wheat to get the young seedlings off to a good start and carry the wheat through the winter.

Our approach has been to fertilize winter wheat according to soil samples taken in the early spring. The soil samples allow for 25 pounds less  N due to the fact we’re seeding wheat following a legume, so there is some reduction in nitrogen requirements following the field pea crop.

We don’t reduce the N requirement for winter wheat any more than this reduction from the soil testing lab. We assume any N produced by the field peas may not be in a plant-useable form if the N requires 18 months to convert to plant-available N.

My observations over this time of producing field peas is that our winter wheat yields have been very good following this method of determining N requirements for the winter wheat crop. We’ve had good yields of winter wheat and have maintained good protein levels in our winter wheat crop.

I think the winter wheat crop may benefit from the N the field peas have left behind as the protein levels in the wheat have remained high with good yields.

My observation for fertilizing winter wheat following field peas would be to follow the recommendations from the soil-testing lab, and I wouldn’t give the field peas any more N credit than the soil lab recommendation.

I do think the protein levels in our winter wheat crop have benefited due to the N from the field peas, and we may see some reduction in N requirements from the field peas in the corn crop we grow following the winter wheat crop.

My observation over time is that we don’t seem to require excessive N to produce our dryland corn crop. I wonder if the N benefits from the field peas may be showing up following the 18 months since the field pea crop.

Next week I’ll take a look at an old nemesis we have seen come back into winter wheat production following the field peas that has developed over time in our winter wheat, corn, field pea crop rotation.