Pine Bluffs Post - Serving all of Eastern Laramie County since 1908

No till notes - cover crops, parts 2 and 3


Cover crops have proven to be an intriguing production practice in modern agriculture. Cover crops have also proven to be equally perplexing. Let’s take a look at everything I think I know about cover crops, which is a little, and all that I don’t know which is considerable.

What has gotten me so interested in cover crops and especially cover crops grown for grazing cattle is the testimonial I’ve heard from farmer/rancher friends of mine and others I’ve listened to at meetings who have some amazing results on their farms and ranches from the production of cover crops. Producers who have been raising cover crops and grazing them for forages are now producing outstanding yields of cash crops such as corn, wheat, and other cereal grains without any commercial fertilizer.

When I’ve visited with these producers about their yields and their use of cover crops they explain to me that the key to their success is improving their soil’s health. When they produce these cover crops they are improving the soil organic matter, increasing the water holding capacity of their soil, and increasing the microbial diversity and populations in their soil. This improvement in soil health has allowed them to reduce their inputs of commercial fertilizers in their cash crops making their operations more profitable.

The key to these cover crops is adding diversity into the plants we grow in our soils. This diversity includes diversifying and increasing the soil microbial community which releases more nutrients for the plants we grow as cash crops. I’ve spoken to soil microbiologists who have explained to me the complicated world of soil microbiology. My general understanding is if your soil has the right combination and populations of soil microbes the soil is capable of supplying many nutrients to the plants.

I find this whole concept of soil health very interesting. I’m also looking at ways to adopt this concept of plant diversity into our own farming operation. My main goal is to reduce my production inputs of commercial fertilizer to improve the profitability of our farming operation. Improving the health of the soil we work with is also a goal.

Twenty years ago we started down this path with the adoption of no-till crop production practices on our farm. We have also added legumes to our cropping rotation which has added diversity to our production system. This past year we planted a cover crop for grazing cattle after we harvested our irrigated winter wheat. We have a couple of on farm experiments on our dry land corn crop as well as our irrigated corn crop which we planted into our cover crop that was grazed during the winter.

Let’s start out by taking a look at the irrigated corn crop we are growing following the cover crop for grazing. I really like the idea of growing the cover crop following our winter wheat harvest. By growing the cover crops we have a living root in the soil growing as opposed to a long fallow period prior to planting corn the following spring. This time period is ideal for adding diversity to our cropping system as well as producing forage for cattle. The only downside to this production practice is the fact we had to pump 5 inches of irrigation water on the cover crops to produce them.

The cover crops we planted were 80 lbs. of field peas/acre, 2 lbs. of sunflower/acre, 5 lbs. of flax/acre, and 2 lbs. of nitro radish/acre. Our seed costs were $8 per acre for everything but the field peas which we grew ourselves. Adding in the value of the field peas total seed costs were approximately $20 per acre.

The cattle really utilized the cover crop and we grazed approximately 300 head of cows for a month on this cover crop mix. We were very careful not to overgraze and we left 50 percent of the residues to maintain good soil cover. These residues will reduce the soil moisture evaporation and help feed the soil microorganisms.

Next week we’ll look at our farm experiment on this field including biomass sampling of the cover crop, soil testing, soil microbe testing, and the Haney test for nutrient release from these soil microbes.

I wanted to show you why I think producing cover crops for forage is so intriguing and what we have learned up to this point with our on farm experiments. This will also point out why we need more research into soil health and the economic benefits of improving soil health.

We raised cover crops following our irrigated winter wheat harvest last fall. We had a neighbor graze his cattle on these cover crops in March, then planted the field to corn this May.

Last fall we had a biomass sample tested of the cover crops residues which showed there were 174 lbs. of nitrogen per acre in the cover crop’s residues and the other residues from the crop’s we had grown previously that were still on the soil surface. There were other plant nutrients in the sampling as well, but I want to focus on nitrogen for the time being.

We had a carbon to nitrogen ratio of 39 parts carbon to 1 part nitrogen in this biomass sample. After visiting with Ray Ward whose soil testing lab performed the testing of the biomass sampling, we decided there would be approximately 50-60 pounds of nitrogen available for the corn crop.   

We soil sampled this field in the spring to see how much commercial fertilizer would be required to produce a 200 bushel per acre corn crop. As we expected there was very little residual nitrogen in the soil. In the top 3 feet of soil there was only 20 pounds of nitrogen. The cover crops had absorbed most of the nitrogen in the soil and moved it up into plant material. The soil sample test recommended 220 pounds of commercial nitrogen needed to be applied for our 200 bushel per acre yield goal.   

Our crop consultant determined we had a corn plant stand of 34,000 plants per acre. He felt that this field of corn has the yield potential of 220 bushels per acre. This yield goal would require approximately an additional 25 pounds of nitrogen which would raise our nitrogen requirement to around 245 pounds of total nitrogen needing to be applied to the field.

We planted the corn and applied approximately 10 pounds of nitrogen with the planter. After planting we sprayed another 50 pounds of nitrogen per acre on the field with our sprayer.  We also have applied an additional 100 pounds of nitrogen through our center pivot when we irrigated the corn crop.  Our total applied nitrogen to this field has been 160 pounds per acre.

With a yield goal of 220 bushels per acre our nitrogen requirement from the soil test is 245 pounds per acre. We have applied 160 pounds. This leaves us with a nitrogen deficit of 85 pounds per acre.

We also have tested the field for soil microbes which showed we had a good population of soil microbes and good diversity of soil microbes. We also tested the field using the Haney test to determine how much mineralization of nutrients we could expect from these soil microbes. The Haney test indicated we have enough soil microbes in the soil to supply a large portion of our nitrogen needs for the corn crop. The Haney tested indicated we needed only 92 pounds of commercial nitrogen fertilizer for a 200 bushel per acre yield.

You can see why I find this idea of cover crops and soil health so interesting. We tissue sampled the corn crop and the results from this testing indicated we have sufficient to high amounts of nitrogen for our yield goal of 220 bushels per acre. We have applied approximately 85 pounds per acre less nitrogen than traditional soil sampling would indicate we needed to apply. We have also applied approximately 70 pounds more nitrogen than the Haney test indicated we would need.

Have we over fertilized our corn crop or under fertilized the crop? I don’t have the answer to that question. How much nitrogen can the microbes and residues provide? I don’t have an answer for that either.  I really think these are questions we need answers to so we can determine an economic benefit to producing cover crops for forage.

We plan to tissue sample the field again next week to make sure the plant has the nitrogen necessary for high yields. I’ll let you know the results of this test when I get them back.


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