By Sjoerd Willem Duiker
Over the last century the prevalent scientific recommendation has been to exclude (ruminant) livestock from cropland. The quest for higher productivity was pursued through greater control over the factors of production resulting in separation of crop and animal husbandry. These recommendations led to things like continuous corn, pure alfalfa, corn-soybean, wheat-fallow, continuous cotton, confined dairies, beef feedlots, contract hog and poultry production, integrators, and so forth. We are now finding that this lack of diversity in our farming landscape has unintended consequences such as rising costs and greater risk of production, manure excess in some regions and nutrient deficits in others, eutrophication, air pollution, loss of soil organic matter, reduced soil health, a Dust Bowl, loss of pollinators and biodiversity, increasing animal health problems, fewer farmers, rural depopulation, and more.
Now, a movement has arisen that may counter these trends. Some producers, and consumers alike, show an interest in a return to more 'natural' methods of production. It is realized that the diversity that characterizes natural ecosystems has built in checks and balances that buffer these systems to shocks and environmental problems, and provide life to multitudes of organisms, including man. The new form of farming that aims to emulate nature is captured under the term 'regenerative farming.' It goes beyond environmental conservation to environmental improvement. Although regenerative farming has many interpretations, it generally involves bringing ruminant livestock back to cropland, where they graze cover crops and crop residues after crop harvest.
Bringing grazing animals back to crop farms involves quite a change in thinking and practice. How to avoid the animals from escaping to roads and neighboring properties? How much time will be involved moving animals? How to get water to the animals? Will the animals cause detrimental soil compaction, or will their manure, urine and grazing habits help improve soil health? And what are the economics of grazing cover crops? To answer these questions, we studied the soil health, productivity and profitability aspects of grazing cover crops on four long-term no-till farms in southcentral Pennsylvania. No-till was considered to be important because in permanent no-till, the soil becomes more resilient and resistant to compaction, while the soil is protected from erosion as well. Farmers had to learn about grazing cover crops and install fencing and watering systems, while the researchers designed a research protocol to study the soil health and profitability aspects of grazing cover crops in a joint project with Capital RC&D, USDA-NRCS, Conservation Districts, USDA-ARS and Penn State Extension.
Farmers installed permanent high-tensile fencing around the edge of their farms, while they obtained mobile electrified fencing to avoid the animals from escaping into neighboring crop fields, and to facilitate Management Intensive Grazing (MIG). MIG involved daily moves of the animals, where the animals are allowed to consume only a portion of the standing biomass, while the remainder is left standing to either regrow or as mulch for the following crop to favor soil health improvement. The cover crops were often grazed more than once, in which case a sufficient rest period was included after each grazing event, allowing the soil to recuperate from the grazing impact, and the cover crop to regrow until it was ready for repeat grazing. Buried water pipes were installed to bring water to the edge of the field, while above-ground flexible water pipes with quick connects were used to bring water to the paddocks that changed every day. The farmers spent about 20 minutes every day to move the animals, some of which were purchased specifically for this project.
The researchers went out about 2-3 weeks after farmers started grazing a cover crop field to measure standing and post-grazing cover crop biomass, and soil health before, the day after, and 2-3 weeks after grazing. Soil health parameters measured were water infiltration rate, soil bulk density, aggregate stability, organic matter, active soil carbon, and carbon-dioxide burst. The cover crops were planted after corn silage or after wheat harvest. Fall planted cover crop species after corn silage included triticale, wheat, annual ryegrass, hairy vetch, and crimson clover, while summer cover crops planted after wheat included pearl millet, sorghum-sudangrass, sunnhemp, sunflower, cowpea, radish, and forage rape. Many times, mixtures of these were planted together, increasing biodiversity.
We determined that soil health on all farms was excellent, and not affected by grazing. While we hoped for a positive effect of grazing, we were pleased to see that grazing did not lead to detrimental soil compaction. Further, the amount of consumed cover crop biomass varied from 1000-2300 lbs drymatter per acre per grazing. Depending on regrowth the farmers grazed 1-3 times. The farmers left always at least 50% of standing biomass for soil function and protection. We calculated the economics of grazing cover crops after corn silage for each farm, considering the investments in permanent and mobile fencing, buried and above-ground water systems, the labor needed to move the animals (at $20 per hour), and the value of the grazed biomass (at $190 per Ton). We assumed permanent fence and buried water had a lifespan of 40 yrs, mobile fencing 20 yrs, and above ground water 10 years, and used a 5% interest rate. We determined that net value of grazing varied from $48 to $233 per acre per year.
One big factor determining profit was the number of times the cover crop could be grazed, and the quantity of grazed biomass consumed. Further, the cost of exterior fence was another big factor – by fencing in a larger, regularly shaped area, the costs per acre could be reduced. Further, the amount of time spent moving the animals could also be a big cost which could be reduced primarily by having more animals in the herd or reducing travel time to the field. Altogether, the farmers were very pleased with their grazing cover crop experience and most are expanding the practice on their farms, while figuring out how to do it better. Another important finding was that the environmental functions of cover crops (such as its effects on soil health and water infiltration) can be preserved while grazing them, at least if done in permanent no-till and using Management Intensive Grazing practices.
Source : psu.edu