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Soil Health Resource Guide

#interseeding

By January 15, 2018December 10th, 2019No Comments

Companion Cropping/Interseeding

Since many farmers struggle to incorporate diversity into their crop rotation, some are looking to push the traditional boundaries by growing cover crops within the commodity crop during the growing season. Before pre-emergence herbicides were standard practice, it was common to seed pumpkins or other crops in between rows of corn to gain an additional crop in the season at “layby” time. Modern experimentation with this interseeding concept has been going on for the last several years, but this technique is still very much in its infancy and has a number of obstacles to overcome. The best results have occurred when covers are interseeded in corn between the V3-V7 stage and a stand gets established before the corn canopies and sunlight is lost. Initial success has come using soybeans, cowpeas, clovers, and annual ryegrass as companion crops. Drilled stands almost always perform better than broadcast seeds, even in high moisture conditions. Since the corn is already established, the emerging cover crop does not grow enough to cause yield reductions in the corn, but grows rapidly once the corn canopy is removed in fall. We encourage you to experiment on a small scale, but pro-ceed with caution and check with your crop insurance agent to maintain compliance.

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Interseeding into

Cool Season Grass Pastures

Cool-season perennial grasses, such as brome, bluegrass, orchardgrass, and fescue, require a great deal of nitrogen fertility for optimum growth and usually grow very little during the heat of summer. These factors have led some people to experiment with drilling or broadcasting other crops into these grasses to increase forage production or fix nitrogen with interseeded legumes. Drilling spring peas, lentils, or chickling vetch in either fall or early spring can provide both additional forage and nitrogen fixation as soon as 60 days after planting, though these species are short-lived. Broadcasting or drilling a blend of red clover, ladino clover, annual lespedeza, chicory, and plantain in either late summer or winter can extend the grazing season further into summer, as well as provide all the nitrogen needs of the stand. This blend takes a while to begin production, but the plants persist for many years. Doing both practices at the same time can provide excellent initial production along with long term benefits. Teff grass or improved varieties of crabgrass can also be broadcast in spring to increase summer production. Other innovators have discovered that they can graze cool-season pastures down in the late spring, then drill a blend of warm season cover crops such as sorghum-sudangrass, BMR grazing corn, pearl millet, cowpeas, and sunn hemp for grazing in late summer for an incredibly high yielding pasture. One eastern Kansas farmer has recorded yields of over eight tons per acre of cover crop dry matter on this system, all produced after a late June grazing of his fescue-clover pasture. He has done this for four years running and his fescue looks better than ever, far better than that of his neighbors.

The picture below shows his warm season cover crop mixes growing in the grazed out fescue pasture. Eight tons per acre never looked so beautiful!

Interseeding into

Warm Season Grasses

Warm-season grasses can be tremendously productive, but have a very short growing season, letting a large amount of sunlight go unutilized. Interseeding a cool-season species can add to total production, extend the grazing season, improve soil biology, and fix nitrogen if legumes are used. While we are not suggesting this as a practice in pristine native grasslands, many pastures have been broadcast sprayed with herbicides and have had their legume and forb component eliminated. Desirable characteristics of a species to interseed into native grass would include high cool-season productivity, low competitiveness to the perennial grass, forage quality, and ability to fix nitrogen. Species that may merit consideration with this practice include sweetclover, winter lentils, crimson clover, and balansa clover. We encourage experimentation with this practice on a limited basis to learn which species are most successful.

Cover Crops in a Cotton Rotation

In some areas of the southern plains, cotton is still king, but because cotton is a low-residue crop, both wind and water erosion is a real concern. Cotton rotations present both real opportunities and real challenges for cover cropping and soil health. There are three time frames to look at when establishing cover crops in a cotton rotation: early spring, prior to harvest (early/mid fall), and post-harvest (winter). 

In early spring, cover crops can be planted when soil temps reach 45°F. A nice diversity of species can be used, but since residue is critical to maintain in a cotton rotation to prevent erosion, the majority of the mix will be grasses like oats, barley, or spring triticale. Species that have a darker residue when terminated, like flax, phacelia, and faba beans, will allow for more heat absorption for early planting but will still maintain residue. Other springtime species to consider adding include Hubam clover, spring peas, woolly pod vetch, or chickling vetch. 

Seeding a cover crop prior to cotton harvest is becoming more common as growers have been having some excellent success with this method.

Jeremy Brown, owner of Broadview Agriculture in Lamesa, Texas, has been successfully broadcasting a cover crop before defoliation of the cotton and before the September rains. Jeremy has been focusing on his soil health for the past nine years by utilizing cover crops and no-till. In southwest Texas, moisture is a huge factor for farmers, so Jeremy’s goal is to properly utilize and manage cover crops and crop rotation to catch every drop of moisture (through better infiltration and no runoff) and to keep that moisture in his soil (by keeping the ground covered to prevent evaporation). Brown typically uses cereal rye, hairy vetch, and radishes in his environment, but he isn’t afraid to try new species in order to diversify. Jeremy notes, “One of the more valuable things I have learned is that we have to allow enough time in the spring for the cover crops to grow in order to get the benefits, while at the same time managing for maximum moisture use efficiency. It is a delicate balancing act.” Jeremy shares much more information and lots of great videos on their Facebook page:

www.facebook.com/BroadviewAgricultureInc

Tom Cannon of Blackwell, Oklahoma, is also a successful practitioner of the pre-harvest seeding method. Tom says, “We flew on a mix of winter lentils, white clover, cereal rye, annual ryegrass, turnips and flax around September 11th but I will try to be a little bit earlier next year as an earlier planting date would have given me more grazing potential. We let the frost desiccate the cotton and apply a boll opener 5 days before the frost, which does not harm the cover crop. We did this on 450 acres and I wish I had done it on 1,000 acres as we will graze these covers in the spring and then plant soybeans in June.”

Lastly, planting cover crops after cotton harvest is possible but it is typically limited by lack of growing degree days as cotton is not harvested until November or December. Cereal rye and hairy vetch are the best choices here as they can establish late in the season. If harvest is delayed into late December and January, utilizing clovers along with cereal rye and vetch in a frost seeding scenario can be beneficial, but waiting for a spring plant window may still be the better choice. For more information about seeding cover crops into cotton, please contact one of our sales representatives from the back cover.

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