Soil Management for Integrated Crop-Livestock Systems
Types of Integrated Crop-Livestock Systems
The most commonly practiced integrated crop-livestock systems in the United States are livestock grazing of cover crops within cash-crop rotations or grazing of crop residues.
Grazing Cover Crops and Crop Residues
Cover crops integrated into crop-livestock operations provide many benefits. Many producers consider cover crops a success only if yield of the subsequent cash crop increases. It is important to state that net margins per acre for cash crops are determined more by input costs than by yield per acre. Cover crops provide a wide range of services, whether planted following a cash crop or interplanted, can increase soil organic matter, improve soil moisture holding capacity, help prevent soil erosion, limit nutrient runoff, and reduce soil compaction. Producers who have been using covers for several years also report reduced weed pressure in cash crops, and lower pest and disease pressure on their cash crops.
Cover Crops for All Seasons
Cover crops are usually annual forage crops that can be planted in the fall after a row crop (soybean, corn, or cotton) harvest or in the summer after a wheat harvest.
Summer Annuals (Warm Season). Summer annuals, otherwise known as warm-season annuals, prefer warmer soils at planting, making them ideal for crop rotation with small grains or early harvested crops. If the goal is to maximize yields of the summer annuals or stored forages followed by late grazing, their planting time would be like that of corn and soybeans, giving them a longer growing season. Sudangrass is a summer annual grass that can be positioned into a crop rotation to provide grazeable forage during the typical summer slump in cool-season grass growth.
Winter Annuals (Cool Season). Winter annuals, or cool-season annuals, are crops planted from late summer to early fall, grown over winter, which can be harvested in both the fall and the subsequent growing season. Many of the species considered options for cover crop grazing are also regarded as row crops. Two types of cool-season annual forages that are well-suited to produce forage are small grain cereal grasses, such as oats, cereal rye, triticale and wheat, and brassicas which include turnip and radish.
Intercropping with Cover Crops for Forage
Crop managers may consider using interseeding tactics to establish cover crops for grazing. Establishing clover into vegetative wheat during the winter is an old practice that will normally result in a large amount of forage growth after wheat is harvested for grain during the summer. Forage grasses can also be planted with wheat in the fall. Another technique involves establishing cover crops into vegetative corn during the V-4 to V-6 stages with the goal of having well-established cover crops after corn harvest.
Managed Grazing
Some farmers growing cover crop grazing find they get optimum returns by using intensive grazing management techniques with low-cost, portable electric fencing and regular moves of livestock between paddocks. Daily or near daily moves not only lead to more efficient use of cover crop forage but also reduce potential hoof damage to crop fields. Strip grazing is recommended to increase grazing days and efficiency. Strip grazing is achieved by fencing off a portion of the field with electric fence to reduce selective grazing and utilize corn residue more efficiently.
Livestock Grazing/Animal Impact
The cover crops mix planted and timing of the grazing are critical. For the cover crop to be terminated, it has to be at the correct stage of its life cycle. Usually this means it has finished pollinating. High stock densities are required to trample the cover crop. While high stock density grazing can significantly reduce opportunity for the cover crop to interfere with the subsequent cash crop, it will not create or cause complete termination of the cover.
Grazing of Crop Residues
Grazing annual crop residue works with an annual row crop system where the grain is harvested and the residues are grazed during the dormant periods in the autumn, winter, or dry season. Although crop residues do not meet annual feed needs, it reduces feed costs and improves nutrient and carbon cycling. Cattle grazing of corn residue in winter is common in the Great Plains and has been shown to increase soil health and crop yields. This process involves grazing the corn residue left behind after harvest—namely the stalk, leaf, husk and cob, as well as downed ears. Through this system, producers can utilize available forage resources while reducing stored feed costs and respective operating costs. In some cases, farmers also leave some of the grain unharvested (corn or sunflowers, for example), enabling forage access for the grazing animals during the winter, even with deep snow. Cows grazing cornstalks or grain sorghum stubble will consume 25 to 50 percent of the available residue in 30 to 100 days, depending on stocking density or stocking rate, leaving enough material to prevent soil erosion.
Swath Grazing
Swath grazing is an alternative forage handling method that offers the potential to lower winter feeding costs. This technique involves cutting hay, leaving the residue in windrows, known as “swaths,” and allowing livestock to graze the windrows during the winter. Swath grazing can be utilized with various crops and can improve utilization of the crops for feed, while decreasing fuel, harvest and feeding costs and also improving soil health. Producers who currently utilize swath grazing are mostly windrowing annual crops such as oat and barley, but perennial hay crops and late-seeded oats or barley have also been successfully used.
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