Widespread adoption of no-till systems in Pennsylvania, together with improved weed control, fertilization, plant genetics, and planting equipment, has greatly expanded the opportunities to integrate grazing into cropping systems. No-till systems enhance soil conservation, which provides improved surface organic matter content and a firm soil matrix that resists soil compaction by grazing animals. This leads to a more abundant and diverse soil biological community that improves aggregation and porosity to alleviate compaction, and makes it easier to diversify cropping systems with crops that can be grazed by reducing the expense and time required to prepare a seedbed.
Grazing is a low-cost method of harvesting livestock feed; the cost of grazed forage is typically half or less of that of harvesting, storing, and feeding with machinery. In addition, in a controlled grazing management system, there is no need to spread the manure and urine of grazing ruminants. The time spent managing the animals is therefore compensated for by the time saved harvesting, storing, feeding, and spreading manure in confined operations. By using management-intensive grazing systems in which animals are moved to a different paddock every few days or even hours, manure distribution is much improved compared to continuous grazing. Below are some opportunities to integrate grazing into no-tillage cropping systems.
Rotating Cool-Season Perennial Pastures with Annual Crops
The benefits of perennial sod compared to annual crops are well documented and include reduced nitrogen losses (especially nitrate leaching losses), reduced soil erosion, improved soil organic carbon, improved soil structure, improved soil water-holding capacity, higher subsequent crop yields, reduced fertilizer nitrogen requirements, and reduced insect, disease, and weed pressure. In a long-term crop rotation trial in central Pennsylvania, corn yields after a four-year perennial sod crop of orchardgrass/alfalfa were increased 15 percent in the first year after sod, 10 percent in the second year, 8 percent in the third, and 7 percent in the fourth year because of soil health improvement and other benefits.
Farmers have found it beneficial to grow annuals for a year or two in a pasture renovation program. By using no-tillage, the soil improvement benefits of the perennial sod crop are maintained. Research from the southeastern United States showed that the positive soil quality benefits achieved during the pasture phase were preserved when no-tillage was used. While in these cases the perennial sod is killed before annual crop establishment, it is also possible to overseed annual forages into dormant perennial forages. This is practiced routinely in the southeastern United States, where annual ryegrass and/or crimson clover are overseeded in the fall with no-till practices into dormant perennial bahiagrass or bermudagrass, boosting fall and spring grazing potential.
Figure 1. The effect of crop rotations on corn yield in a 16-year crop rotation trial at Rock Springs in central Pennsylvania. CC = continuous corn; CS = corn-soybean rotation; CCCCAAAA = four years of corn, four years of alfalfa/grass rotation, with the first bar being first year of corn; second bar, second year of corn; third bar, third year of corn; and fourth bar, fourth year of corn after alfalfa/grass hay; COWRR = corn-oat-wheat-two years of red clover timothy hay rotation. Percentages above the bars show the corn yield increase in percent compared with continuous corn.
Grazing Cover Crops
Cover crops are considered to be among the most cost-effective practices to improve environmental performance of annual cropping systems. Cover crops help reduce soil erosion by protecting the soil from raindrop impact and runoff scouring; reduce nitrate leaching by absorbing any soil nitrate that is left over or released after main crop harvest; alleviate soil compaction through their root systems; increase soil organic matter content and improve soil health; take up nutrients from manure applied in the off-season, protecting them from loss to surface water or groundwater; fix atmospheric nitrogen (in the case of leguminous cover crops) that can benefit following crops so less fertilizer is needed; and add mulch cover for soil protection, water conservation, and feeding of soil organisms in the following main crop.
Cover crops are typically annual species grown after main crops are harvested and occupy the field when it would otherwise be fallow. Cover crops may be established after the main crop is harvested, but they can also be planted into a standing crop. By grazing cover crops judiciously, most environmental and soil health benefits can be maintained while an immediate economic benefit is obtained. This makes it much easier for a farmer to justify the time and expense involved in cover crop establishment and management. By using no-till, the cover crop can be established quickly (immediately after harvest), which guarantees better growth of the cover crop than if soil had to be plowed and a seedbed prepared after harvest of the main crop. Research at Penn State has led to the development of a no-till interseeder that can be used to interseed cover crops into standing corn or soybeans within six to eight weeks after planting. This way the cover crop will already be present when the main crop is harvested. Another opportunity is to broadcast red or sweet clover seeds into standing wheat or barley in February or March. The action of soil freezing and thawing and the high moisture content of the soil usually result in acceptable germination and a good clover stand. Broadcasting is usually not effective when done in the summer because there is not enough moisture at the soil surface and perhaps because soil critters like slugs eat the small seedlings. Many farmers are concerned about the threat of compaction when cover crops are grazed. However, in research in the Piedmont of Georgia where cover crops were either grazed for 47 days by cow-calf pairs or left ungrazed, no compaction and degradation of the soil due to grazing were observed.
In case studies in Pennsylvania we did observe compaction of the surface of the soil immediately after grazing, but the compaction dissipated if the paddock was rested for a period of 20 days or more before it was grazed again. Soil compaction needs to be monitored carefully, and if you see “pugging” (places where cattle sink into the soil), it is time to move the animals to a drier paddock or to a hard surface until conditions are fit. Many cover crops have very good feed quality if grazed in the vegetative stages.
Figure 2. In integrating grazing into no-tillage systems, the farmer relies completely on biological activity of organisms such as earthworms, fungi, bacteria, and root systems to improve the ability of the soil to resist compaction and to remediate the effect of compaction caused by grazing animals. However, the farmer needs to observe if pugging is being caused by the animals under wet conditions, at which point the grazing animals should be removed from the paddock. Photo courtesy of Sjoerd Duiker
Grazing Crop Residue
Grazing crop residue is one of the simplest and cheapest ways to feed livestock. Grazing corn residue is widely practiced in the western Corn Belt and east-central Great Plains region, and could be more widely used in Pennsylvania as well. In the Corn Belt, beef cows are usually grazed on rangeland in the summer and then after harvest are transported by truck to the cropland where they are grazed for a fee. The animals may not belong to the farmer who owns or farms the cropland. Corn residue can supply grazing for 250 to 370 animal unit (AU) days per acre for ruminant animals. One AU is 1,000 pounds of liveweight of animal. The quality of corn stover is sufficient to feed dry cows and mature bulls; however, if growing heifers, steers, bulls, or lactating or pregnant cows are grazed on corn reside, a protein supplement is needed to meet their dietary needs.
Grazing crop residue is an effective way to save money on hay or haylage to feed these animals in the winter. Research has shown that grazing corn residues decreases residue cover by only 5 to 25 percent, so erosion control is not compromised. Grazing is a much more cost-effective method to harvest crop residue than baling it and bringing it to the animals. Soil compaction by animals is a prime concern when grazing crop residues, just like when grazing cover crops. However, because there is no living root system in the soil if no cover crop is present, the danger of soil compaction is greater. Nonetheless, crop residue can be grazed without detrimental soil compaction if the land is grazed when the soil is frozen or relatively dry, surface soil organic matter content is high because of years of no-tillage management, and large quantities of crop residue cover the soil, acting as a blanket. The key is to monitor soil conditions. If you see pugging of the soil surface by the grazing animals, then it is time to remove them from the field to avoid negative consequences for the following crop.
Repeated freeze-thaw cycles also help to alleviate soil compaction. If there is a highly active soil biological community, the soil will bounce back from compaction better than if soil biological activity is low. In most cases in Pennsylvania snow cover is not a concern for grazing animals unless the snow is very deep or it melts and becomes a thick layer of ice that the animals cannot break through. Although crop residue can be grazed, it is recommended to drill a winter-hardy cover crop even if it is late in the fall. The cover crop may not emerge before winter falls in, but it will still produce growth in the spring.
Figure 3. Grazing corn stover can be a cost-effective way to reduce the need for hay or haylage. However, it is preferable to plant a cover crop immediately after corn harvest. Photo courtesy of Jessica Williamson
There are many opportunities to integrate grazing into no-tillage cropping system, such as grazing perennials in rotation with annual crops, grazing cover crops, and grazing crop residues. One option we have not mentioned is grazing small grains that will subsequently be harvested for grain. While it is a common practice in the southern Great Plains, it still needs to be evaluated in Pennsylvania. Another option—grazing forages established between young trees (silvopasture)—in new plantations is another example of a practice that has not been evaluated in our state but could offer potential to get some extra income out of young tree stands. But the three examples we have detailed here show great promise to improve profit, increase diversity, and improve soil health on our crop farms. With new crop management practices, such as continuous no-tillage, increased weed management options, new seeding technologies, and management-intensive grazing, grazing can be successfully integrated into crop production while soil health is maintained or improved.
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Franzluebbers, A. J., and J. A. Stuedemann. “Early response of soil organic fractions to tillage and integrated crop-livestock production.” Soil Science Society of America Journal 72 (2008): 613–25.
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Prepared by Sjoerd W. Duiker, professor of soil management and applied soil physics, and Jessica A. Williamson, assistant professor of forage management.
This material is based upon work supported by the NaturalResources Conservation Service, U.S. Department of Agriculture; under number 68-2D37-14-743.