Infiltration Improved by use of Cover Crops
Infiltration is the process of water entering the soil. Infiltration rate is a measure of how fast water enters the soil. Water entering too slowly may lead to ponding on level fields or to erosion from surface runoff on sloping fields. Reducing erosion and runoff also reduce surface runoff of fertilizers and chemicals such as herbicides. Fertilizers and herbicides are agronomic inputs to assist farmers in producing productive and profitable yields. The objective of applying nutrients and herbicides and other chemicals are to benefit the plant. If the inputs runoff, it is a loss to the farmer and the environment.
Plants need water and sunshine to produce crop yield. Infiltration is dependent on soil type, soil organic matter and aggregate stability or soil structure. As farmers utilize conservation practices that increae soil organic matter, soil health indicators such as soil structure, aggregate stability, and infiltration will also improve.
Rainfall simulators have become quite common in Tennessee. NRCS uses them to demonstrate how cover crops, no-till, and good grazing practices improve infiltration and reduces erosion. Below is an example of rainfall simulator at Milan No-till Experiment Station on Soil Health Plots.
The five trays used were from five treatments left to right, no-till only, NT wheat only, NT cereal rye and crimson clover, NT five-way mix consisting of cereal rye, wheat, crimson clover, daikon radish, and purple top turnip, and NT cereal rye and vetch. Rainfall simulations were run multiple times totaling 3" of water. All trays had good soil structure due to long-term no-till. As you can see by the back jugs showing infiltration, the 5-way mix infiltrated the best.
In another demonstration, the picture below shows minimum tillage (it is still tillage), no-till, over grazed pasture, conventional tillage tobacco with an excellent cover crop, and good grazing. Note that the good cover crop and the good grazed grass infiltrated and had little runoff compared to other treatments which had high runoff and poor infiltration.
So, all that is demonstration. Let’s put this to the test to real field conditions and real rainfall. Matt Griggs who is featured as the Number 3 in the Profiles of Soil Health Heroes on tnacd.org and also Matt Griggs update Profiles of Heroes. Matt recently sent me pictures in a rainstorm at his farm, true dedication.
Cover crops add more carbon and increases soil biology that increases better aggregates which results in much greater soil structure, pore space, thus better infiltration rates. Pictures below show long-term no-till with standing water, four years plus of cover crops and no-till with great infiltration, and the bottom picture show where the two plots come together. A picture is worth a thousand words. Cover crops with no disturbances from tillage improve soil function, such as here, infiltration.
Twenty Years of No-till. Two years of multi-species cover crops and no-till.
No-till alone on the left and No-till with cover on the right.
Soil health is improved by not disturbing the soil, keeping a root growing, keeping the soil covered, and diversity. The demonstrations and real farm application show continuous no-till with cover crops improve the soil’s ability to infiltrate water. Better water infiltration means better efficiency of water use and more stable yields. Contact the Bedford County Soil Conservation District office for more information @ 931-684-1441 ext.3
Guidance for Using a Roller/Crimper
Cover crops are significantly important in keeping no-till systems healthy. In any system, cover crops provide valuable benefits to the soil such as reducing erosion, soil compaction, nitrate leaching and weed pressure. Cover crops also increase the amount of organic matter, keep the soil cooler, and provide a source of nitrogen (legumes) while improving soil fertility, water infiltration and water storage capacity. One important component of cover crop management is choosing how to kill the cover crop before the cash crop is planted. This Fact Sheet provides guidance on utilizing a roller/crimper which is one of the methods available to kill the cover crop. Roller technology is used with the taller grass cover crops (cereals) and with the shorter cover crops that have flowered.
The benefits of the mulch created by using a rolled and crimped are:
(1) Better weed control, especially early in season;
(2) Cooler soil and improved moisture retention in mid-summer;
(3) Maximum soil protection from raindrop impact and erosion;
(4) Improved digestion or decomposition of cover by soil life resulting in improved nutrient cycling;
(5) Better environment for some beneficial insects and soil organisms such as earthworms;
(6) Reduces environment for voles; and
(7) No bare soil for cleaner picking and products (e.g., pumpkins).
Those considering a roller/crimper need to consider certain factors. When rolling a cover crop without herbicides, the cover crop needs to have flowered or reach reproductive stage. If the goal is to kill the crop without herbicides (organically) then fewer species should be in the mix to have them mature or reach flowering approximately same time. The method of crimping involves rolling down a cover crop that both flattens the cover crop and repeatedly crushes (does not cut) the stems. There are commercial rollers/crimpers available in Tennessee. This Fact Sheet does not cover designs of the crimper/roller. If you have questions on sources of rollers/crimpers, contact your local USDA-NRCS or Soil Conservation District office.
The following items are to assist farmers using either a commercial roller/crimper or more basic device to flatten covers.
1. Methods other than commercial roller/crimpers are available to simply lay the cover down flat. These methods include cultipackers, flat drums, logs, and poles. However, all of these methods will require herbicides to terminate cover crop.
2. If using herbicides, either decide to plant green or plant fourteen days or more after terminating cover based on the type of herbicide used and the cash crop being planted.
3. Since many rollers will be rented, planters will not match rollers’ width. Plant as parallel to flatten cover as possible. Planting at an angle has had successes. Try not to plant perpendicular unless coulters are excellent in cutting through heavy residue.
4. If planting green before rolling, then the rolling direction is not as important.
5. If planting corn, rollers will normally not be beneficial in killing cover due to the cover crop being too early in vegetative growth stage. In this case, the roller is used only to manage the cover laying down to improve function. Leave cover as long as possible to maximize height and biomass and plant green when rolled and treat with herbicides later that day or up to three days to prevent killing the germinating corn crop. However, if one is willing to wait on cover crop to reach bloom stage or early head stage for grasses, then the roller/crimper will be able to kill the cover crop.
6. Later planted crops such as cotton, soybeans and vegetables can benefit from a roller to desiccate the majority of the cover crop if grown to flowering. Keep in mind, carbon to nitrogen ratios increase as maturity of covers increase.
7. Do not use roller for low growing cover crops and early termination. You are wasting your time and money.
8. If farming organic, use single or less number of species to mature at a similar time for a more complete termination.
9. Use roller/crimper to cover the soil and to utilize the allelopathic properties of cereal rye and black oats. Covers that are not laid down on the ground can leave the soil bare. Bare soil does not function as well as covered soil. Rollers are excellent for this objective.
10. Use a more primitive roller (log or pole) if the goal is only to lay the cover crop down. A roller/crimper will do the same and also assist in crushing stem.
11. The goal is to roll/crimp not to bush hog or chop. Keep cover intact attached to soil so the offsite movement or movement to the lower areas of the field is prevented.
12. If your goal is to terminate cover crops using a roller either without herbicides or reduced herbicides, the cover crop must be in bloom to early head stage. Cash crops will be planted later using this method. Mature cover crops can reduce the amount of moisture in soil and termination will need to be based on amount of soil moisture.
13. If cover crops are allowed to mature past bloom for non-grasses and early head stage for grass, nutrients will be tied up in seed and cycled later in season.
14. Roller technology can be used at any scale. Small rollers are excellent for gardens.
Basic Cover Crop Mix 1 (before beans)
Aug. 15 to Oct. 15
Austrian Winter Pea
Basic Cover Crop Mix 2 (before corn)
Austrian Winter Pea
Aug. 15 to Oct. 15