Winter forage and other ways crop-livestock integration improve resilience

Winter forage can minimise erosion while allowing cattle to graze freely during the winter months reduces feed and labour costs. And the large gain in soil organic carbon under perennial pastures is a key climate change mitigation strategy offered by integrated crop-livestock systems.

Author: Alan Franzluebbers. Source: Landscapes for People, Food and Nature    

On a bright sunny day in late March, Steven Knapp walks his cropland fields inspecting the lush growth of rye cover crop that has become an oasis of winter forage for his cattle. Across the road, a neighbour drives by another field – likely in astonishment that the previous night’s rain has washed away so much soil, thinking he will just have to disk up the gulleys once again just like he did after harvesting the previous corn crop. Other neighbours are less dismayed, as they had planted cover crops following their corn crops and felt fortunate that their fields were protected from the storm.

However, Steven is out to inspect his fields up close for evidence of erosion, because his cattle had been grazing the cover crop for a couple of weeks. Maybe they had consumed too much of the protective armor of this cover crop. He was sure he had appropriately stocked with the right number of animals and had planted his cover crop directly into the previous corn crop’s stubble without tillage – a conservation approach being promoted around this region of north Georgia. And to his delight, he’s not finding any evidence of erosion.

In a few weeks when he moves his cattle off the cover crop they will have been fed naturally without the need for supplemental hay for a good month and a half during a time when forage on his permanent pastures was only just starting to green up. The labour savings of cattle grazing on their own on winter cover crops and the added value of cattle weight gain from the investment in planting a cover crop on cropland are major bonuses – and missing from the current practice of planting winter cover crops for conservation alone. Steven is a technician at a USDA research station, so he takes pride in knowing that his work and the research he is engaged with will be extended to other producers so that they can be both more profitable and more protective of the environment they treasure.

Mature cows grazing pearl millet cover crop in foreground while sorghum is grown for grain in the background. Photo: Alan Franzluebbers/USDA

Mature cows grazing pearl millet cover crop in foreground while sorghum is grown for grain in the background. Photo: Alan Franzluebbers/USDA

The short-term cover crops used for conservation and for grazing that Steven Knapp is testing are just one of a variety of agricultural approaches that are well suited for integration of crops and livestock, with significant benefits for environmental health and farmer livelihoods. Integrated crop-livestock systems are characterized as approaches that capture the synergistic benefits of material and energy flows to and from crop and livestock enterprises – whether these exchanges occur within the same farm, neighbourhood, or region. Efficient utilization of resources within such integrated systems is a key characteristic. There is no universal approach, but there are several categories of strategies that can be adopted and adapted to many different ecological conditions.

Livestock raised on grasslands and agricultural cropping using conservation management are capable of coexisting in ecologically-oriented approaches like long-term sod-based rotations, short-term cover crops used for conservation and grazing, dual-purpose use of small grains, pasture cropping, temporally dynamic inter-cropping or relay-cropping, and spatially dynamic strip-cropping, alley-cropping, silvopasture, or integrated crop-livestock-forestry systems. Forages have extensive, fibrous root systems that explore large volumes of soil, mostly in the surface foot of soil, but also penetrating deep into the profile. Perennial forages also extend the growing season compared with annual cash crops, thereby photosynthesizing, depositing rhizosphere carbon inputs, and extracting water from soil during longer periods of time than annual crops.

Sorghum planted for grain with no tillage following grazing of rye cover crop. Photo: Alan Franzluebbers/USDA

Sorghum planted for grain with no tillage following grazing of rye cover crop. Photo: Alan Franzluebbers/USDA

Extreme climate changes will likely affect integrated crop-livestock systems in many of the same ways they affect specialized agricultural systems. However, mixed production systems have some key differences that allow them to both mitigate and adapt to climate change, resulting in potentially less severe impacts.

For example, integrated crop-livestock systems rely on forages as part of a diversity of crop choices. These forages provide a large benefit for positive balance of carbon in the soil. Plus, reduced nitrogen fertilizer requirements for crops grown in rotation with forages will reduce nitrous oxide emissions. The total effect of integrated crop-livestock systems on greenhouse gas emissions – ie carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) – is, however, largely unknown, because the large spatial and temporal complexity of integrated crop-livestock system designs makes projections uncertain.

Nonetheless, the large gain in soil organic carbon under perennial pastures is a key mitigation strategy offered by integrated crop-livestock systems, and also a key adaptation strategy to overcome drought and partially control flooding by improving soil quality when forages are distributed appropriately across a landscape. Forage and grazing lands have historically provided a sustainable and resilient land cover, rooted by a variety of vigorous grasses and forbs and serving as key biospheric engineering components mediating a plethora of essential ecosystem services, notably water cycling, nutrient cycling, gas exchange with the atmosphere, climate regulation, food and feed production, and aesthetic experience.

The diversity of farming operations in integrated crop-livestock systems reduces the overall risk of failure, despite any one farming component being negatively affected as in specialized agricultural systems. This diversity also offers resilience of the farming system against perturbations caused by extreme weather events and climate change. Greater integration of crops and livestock using modern technologies could broadly transform agriculture to enhance productivity, mitigate environmental damage, protect biological diversity, reduce dependence on fossil fuels, provide healthier foods, and increase economic and cultural opportunities in many different regions of the world. When incorporated into diverse agricultural systems that include livestock, perennial grasses and legumes and a wide variety of annual forages offer enhanced agro-ecosystem resilience in the face of uncertain climate and market conditions.

More information on this topic can be found in Chapter 8 (Climate change and integrated crop-livestock system in temperate-humid regions of North and South America: Mitigation and adaptation) of CABI Climate Change Series 5 “Climate Change Impact and Adaptation in Agricultural Systems”, edited by Jűrg Fuhrer and Peter Gregory and published in 2014.

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