Published Sep 3, 2014

Field Day Recap: Jim Gerrish Series

By Margaret Chamas

In a nutshell, there are few other individuals I would be willing to listen to for five days straight.  Yet I thoroughly enjoyed the week of pasture walks and classroom instruction led by Dr. Jim Gerrish, hosted by farmers and sponsored by the Iowa Beef Center, ISU Extension, the Iowa Cattlemens’ Association, local SWCD and NRCS offices, SARE, and Practical Farmers of Iowa.

Dr. Jim Gerrish owns American Grazinglands Services, a consulting business to help farmers and ranchers improve their grazing management.  Dr. Gerrish became well-known through his work on rotational grazing in Missouri, and now manages cow-calf pairs and stockers in Idaho.  The titles of his books encapsulate his philosophy and message: “Management-intensive Grazing” and “Kick the Hay Habit.”  During the week he instructed several hundred attendees on some simple processes and changes they could make to improve forage yield and grazing efficiency (and efficacy) on pastures, as well as a striking look at the real cost of producing hay.

What are you hiring those cows to do?

Dr. Gerrish’s classroom sessions started with an analysis of the cattle farm in terms of a business…one where the farmer is the manager and the cows are the employees.  What are those cows supposed to do as workers?  Suggestions included finding their own feed, delivering and raising a healthy calf every 12 months, and spreading fertilizer.  The farmer as manager is in charge of making sure the cows can do their job, by giving them access to feed.  Ideally, he says that this wouldn’t include (much) haying, since it goes against the cow’s job description.

Dr. Gerrish then went through some calculations of the cost of hay production.  Back when tractor-driven hay equipment first became readily available, prices were such that harvesting hay and feeding it to livestock made sense.  Anymore, he argues, “we feed hay to the extent that we can make hay.”  The cost of an average round bale, garnered from the audience, was always less than the average value of a bale calculated on the screen.  Dr. Gerrish accounted for aspects that most people ignore, like the fertilizer equivalent of exported nutrients ($30-85/ac), equipment depreciation (as much as $40/ac) and stand replacement ($50 to several hundred dollars).  Things added up fast, and it presented strong argument for (at the least) paying someone $12-15/bale to custom hay it, or (at the most) stop haying and start grazing.  Other considerations: the opportunity cost of your time – what could you do with those hours spent in the tractor?  What else could you do with that land?  How are you going to address the movement of nutrients from the soil to a manure pack somewhere else on the farm?

The next question, how to reduce the need for hay, is where management-intensive grazing comes in.  Dr. Gerrish first stresses that it’s the management that’s intensive, not (necessarily) the grazing.  It takes some practice, some skill, and some different equipment, but increasing forage yields and animal gain with well-thought-out grazing schemes has helped him and many others reduce or eliminate their need for stored forages.

“Grass feeds grass, grass feeds the soil, grass feeds cattle”

Among Dr. Gerrish’s main points was that phrase.  If a farmer manages the forage to support itself and the soil first, it will repay him by producing enough for his cattle to eat.

Grass feeds grass: This means that to ensure rapid forage regrowth after grazing, there should be sufficient leaf area remaining to capture sunlight.  Grasses have some stored carbohydrates in the stem base, but using these to produce new leaves takes time and leaves the plant vulnerable.  Leaving two or so leaves on the plant provides enough photosynthetic capacity to regrow more leaves – with minimal use of the carbohydrate stores.

Grass feeds the soil: When harvested either by machines or mouths, forage plants slough some root mass.  The process of growth and die-off contributes greatly to soil organic matter.  With properly-managed grazing, there are multiple “pulses” of growth and die-off in each growing season.  Grazing plants too hard or too often increases the recovery period they must get, and reduces the number of pulses that can be achieved.  Leaving some forage after grazing also helps develop a litter layer on the soil, keeping it insulated, preventing water loss through evaporation, and reducing the risk of compaction.

Grass feeds cattle: Last (though not least), by managing the plants and soil properly, sufficient forage is produced to provide for cattle.  Dr. Gerrish recommended stocking pastures according to the winter carrying capacity, so that the need for hay is reduced or eliminated.  When the flush of spring growth occurs, rather than needing to cut it for hay, he recommends temporarily adding some other animals (such as stockers) to harvest it.  Remove them towards the end of summer, allowing some acres to stockpile for winter feed.  Then since there are only as many cows as can be managed through the winter, there should only in bad years be much need for hay.

Getting the most out of your pastures

After the cow-as-employee example came the cow-as-factory idea.  In the grand equation to producing meat, milk, or fiber by ruminant animals, the inputs are CO2, sunlight, water, and soil minerals.  These are converted into forage by plant processes, which are then converted into salable products by the cow.  To make the process work, the inputs must be captured and used efficiently.  While CO2 levels are out of humans’ immediate control, the amount of sunlight and rainwater captured per acre are, and the amount and quality of soil minerals can be altered within a moderately short timespan.

“Grazing management should be about balancing ecosystem processes, not manipulating inputs,” he says.  “Consider each acre of land as 43,560 sq ft of solar panel or water catchment.”

So, the first step is to build a better solar panel.  Dr. Gerrish explained the concept of leaf area index – the ratio of the area of leaves capturing sunlight, to the area of ground underneath those plants.  LAI increases as plants grow and mature, and as LAI increases so does the percent of available sunlight that is captured by plant tissue.

Maturing plants also go through growth phases.  Phase 1 is the immature plant – think a pasture starting to regrow in the spring, full of lush but low quantity growth.  This is the point when carbohydrate stores are being used to push out new leaves, as mentioned earlier, and in many grasses lasts through the 2-2.5 leaf stage.  Phase 2, through about the 5-6 leaf stage, is a rapidly-growing vegetative plant and is characterized by a great increase in LAI and forage mass: the balance of quality and quantity commonly referenced in graphs contrasting forage mass with forage digestibility.  Phase 3 is mature, headed out forage; while there is great forage quantity it is less digestible and palatable.  Dr. Gerrish recommends harvesting forage at high phase 2 (5-leaf stage) and taking it down to low phase 2 (2-3 leaf stage) – the “take half, leave half” philosophy.  For many cool-season forages, this equates to starting to graze at the 12-16-in. height, and removing animals when there is 4-8 in. left.

Avoid taking “the next bite!”  Having a “fear of wasting grass” leads many people to overgraze pastures, reducing their production within a season, and potentially shortening stand life.  Dr. Gerrish prefers to move animals each day, only giving them as much land (and forage) as they need for that time period.  This minimizes risk of animals regrazing individual plants, encourages more even manure distribution, and (believe it or not) takes relatively little time.  It takes him just under 25 minutes to move several hundred pairs at the ranch he manages.  During the winter, when it might take 30-45 minutes, he still says he’s done and back in the house before his neighbor’s tractor is warmed up.

Leaving some leaf area and frequent rotations also helps with the other portions of getting the most out of the pasture.  The shading by leaves and some thatch buildup help shade the soil and keep moisture in.  Constant root growth leaves pores that reduce compaction and allow water infiltration, and prevent runoff and erosion.  Moving cattle often reduces the incidence of loafing areas and spreads manure out over more of the pasture, stimulating a healthy mineral cycle.  If hay is fed, doing so out on pastures (particularly low-fertility ones) adds organic matter and nutrients back, supporting the bugs, worms, and microbes that will help the soil next year.

Out in the pasture

These concepts were reinforced in the field.  Dr. Gerrish helped participants determine whether a pasture was ready to be grazed by counting the average number of leaves present on plucked tillers.  Many participants were surprised to find pastures in the “right” height range that actually were still in phase 1 or early phase 2.  Dr. Gerrish recommended picking ten tillers on a pasture every week throughout the summer, and tracking the progression over time.  Eventually you will know how long it takes your pastures to regrow at different points in the summer, allowing better management.

The next test was stocking rate – how many animals will a pasture support?  Forming a circle in the field, the group practiced estimating whether the enclosed forage would be sufficient for one animal for a day.  While a standard animal unit is a 1000-lb cow consuming 26 lb of forage dry matter per day, it’s simple to scale the value up or down.  So for a 1500-lb cow, that’s 1.5 x 26 lb = 39 lb forage DM per day.  The group would spread out or close in, to encircle the proper forage amount.  Then the diameter was determined, and the area of that circle calculated.  This could then be divided into the area of an acre, to determine how many cow-days were present.

Dr. Gerrish, with years of experience, has trained himself to be accurate with a 4% standard error.  Anyone else can do that too – each day go visually estimate the area needed per cow, fence off just enough area for the whole herd for one day, and the next day go check the residual.  If it’s been grazed too short, make the area bigger next time; if too much is left, tighten it up a bit.  Within a month, he guesses that most people can train their eye adequately.

Many of the specific numbers, hints, tricks, and ideas are too lengthy to write here – and really everyone ought to try reading or seeing for themselves.  My week of pasture walks was informative and thought-provoking.


These groups also sponsored:

Southern Iowa Forage and Livestock Committee (SIFLC)
Iowa Forage and Grassland Council (IFGC)
Leopold Center