Open Gate Rotational Grazing

An alternative approach to facilitating wildlife and plant diversity in grazed prairie.

Based on the last 20 years of experience and data collection, the shifting mosaic approach to habitat management seems to support plant and animal diversity and foster ecological resilience in our prairies.  One of the most important parts of our shifting mosaic management is that each patch of prairie goes through a progression of season-long intensive grazing, followed by a multi-year recovery period.  At any time, only part of a prairie is in each phase of the system (intensive grazing, early recovery, late recovery), so there is always a variety of habitat structure available (short, “weedy” and tall) for wildlife.  In addition, as that grazing/recovery progression occurs, plant species experience a different set of growing conditions each year.  Regardless of its competition ability or strategy, each plant is ensured favorable conditions for its growth and reproduction at least once every few years.  Based on our long-term data sets, our management has sustained plant species richness, and both conservative and opportunistic plant species are persisting in our prairies.

A fenceline contrast at our family prairie shows the kind of habitat heterogeneity found in a shifting mosaic approach to prairie management.

Patch-burn grazing is one way to create a shifting mosaic, but it’s certainly not the only way.  While patch-burn grazing has some attributes that make it easy to implement (no need for cross fences or moving animals during the season), it does require regular application of prescribed fire, which can be difficult for some landowners.  In addition, patch-burn grazing is very different from the kinds of rotational grazing systems many ranchers are comfortable with and have set up their pastures for.  We’ve been experimenting with an approach to creating a shifting mosaic that keeps many of the wildlife and diversity-friendly attributes of patch-burn grazing but might fit better within the comfort zone and logistical framework of many ranchers.

For lack of a better idea, I’m currently calling this approach “Open Gate Rotational Grazing”.  It is not a rigid prescribed grazing system, but rather a general and adaptable way of managing multiple grazing paddocks within a prairie.  It’s similar to a traditional deferred grazing strategy, but with one big difference.  In most rotational grazing systems, cattle are moved from one pasture to the next, closing the gate behind them to allow the previous paddocks to rest.  In the open gate system, when cattle are presented with their next paddock, the gate behind them remains open – allowing the cattle to continue grazing the initial paddock even as they have access to new grass.

In a traditional rotational grazing system, cattle are progressively moved through a series of paddocks, closing the gate behind them.  In a deferred rotational system, at least one paddock is usually rested for the season.
Under an open gate approach, gates are left open when new paddocks are made available, allowing cattle to graze both the new paddock and the one(s) they had been grazing before.

The idea started one year when we weren’t able to get a burn done in a prairie under patch-burn grazing management.  Since we didn’t have a burned patch to focus cattle grazing, we instead used electric fence to concentrate the cattle in the area we’d hoped to burn.  We kept them in the enclosure until they had it grazed pretty short.  Then we removed the electric fence and allowed cattle to access to the whole site.  For the remainder of the season, the cattle continued to focus most of their grazing in that former enclosure, attracted by the tender regrowth.  As a result, the overall grazing pattern was fairly similar to what we’d expect with patch-burn grazing.  Seeing how strongly cattle were drawn back to where they’d grazed earlier provided the seed for the open gate rotational system.

On my family prairie, I’ve been using the open gate approach for the last several years.  I have four paddocks, and I basically think of the gates between those paddocks as relief valves.  We start with the cattle in one paddock, and when they have grazed most of the grass down in that pasture, I open the gate to an adjacent paddock so they have more options.  The cattle can keep grazing the regrowing plants in paddock #1, but they aren’t forced to eat more than they want to in that paddock because they have another whole paddock available to them.  If the cattle graze down most of the plants in the second paddock, I can open a gate to a third paddock and provide them with even more options.  I keep the fourth paddock closed off for the entire season so it can rest.  I choose a different paddock to start with each year.

The result of an open gate approach is that one paddock is grazed all season long, one is rested all season, and the others have intermediate levels of grazing.  This results in heterogeneity of habitat structure as well as a wide range of growing conditions for plants.  Each year, grazing starts in a different place, shifting the disturbance regimes among the various paddocks.

The open gate approach can be used with just about any rotational grazing system, as long as there are adjacent paddocks that can be opened up.  One key component of the open gate approach is that paddocks grazed early in the season continue to receive grazing pressure for the rest of that season without forcing cattle to eat progressively lower quality forage as the season goes on.  Instead, cattle can regulate their diet freely, choosing between previously grazed areas and those they haven’t yet grazed.  Typically, when cattle are given that kind of choice, they eat very little other than grasses.  This works out well for pollinators because it means many wildflowers are allowed to grow and flower amongst grazed grasses.

At our family prairie, the open gate approach seems to be helping with our continuing quest to increase plant diversity in areas formerly dominated by grasses.  New plants are introduced via overseeding (after a season of intensive grazing), and then persist under our grazing management.

In the open gate system, there is great flexibility about when, and how intensively, each paddock is grazed each year, though some of that flexibility depends on how the paddocks are arranged.  Ideally, all the paddocks would be connected through a single hub so the manager can choose to open any gate to any pasture, as needed.  However, my family prairie doesn’t provide that amount of flexibility (the four paddocks are arrayed in a donut-like loop, with no way to connect them through the donut hole) and the approach still works.  Most of the time, the paddock grazed most intensively one year gets complete rest the next.  However, the pattern of grazing each year always depends upon how I think recovery from previous years’ grazing is going.

I think there are great benefits to longer grazing periods and longer rest periods than are typically found in rotational grazing systems.  Certainly, those prolonged grazing and rest periods can provide a greater variety of wildlife habitat conditions, especially on the shorter and taller ends of the vegetation structure spectrum.  In most rotational grazing systems, cattle are moved out of a pasture before grasses are grazed very short, allowing them to recover quickly.  In addition to reducing habitat heterogeneity, that approach can favor strong grass dominance at the expense of wildflowers and plant diversity.

Even when grazing pressure is intense within each paddock of a traditional rotational system, short duration grazing may not foster habitat heterogeneity.  For example, if a paddock is grazed hard in May, it might suppress cool-season grasses, but warm-season grasses won’t be much affected, and once cattle are removed, summer vegetation will fill in quickly, resulting in vegetation structure of moderate to tall height.  The same can happen with summer grazing bouts followed by fall growth of cool-season grasses.  By maintaining grazing pressure for the entire growing season, two things happen.  First, there is sustained short vegetation structure for wildlife that need it.  Second, and perhaps more important, all dominant grasses are weakened by that long term grazing, leading to a fairly long recovery period (1-3 years, depending upon grazing intensity and geographic location), during which wildflowers and other plant species are temporarily released from that grass competition.  That long recovery period creates terrific wildlife habitat and also helps sustain plant diversity.

While prescribed fire isn’t necessary in open gate rotational grazing, it can certainly be incorporated.  The paddock to be grazed all season could be burned before the season starts, for example, which would further add to its attractiveness to livestock (and remove eastern red cedar trees, excess litter, etc.).  At my own prairie, I haven’t been using fire for a variety of reasons, including that I’m so busy burning for work I don’t have time/energy to burn my own place.  So far, I’ve been happy with the way the prairie is responding in the absence of fire, but if I can get myself better organized, I wouldn’t mind doing some burning.  If nothing else, it would mean less time cutting little cedar trees with loppers.

Prescribed fire is not a strategy all ranchers are willing or able to include in their operations.  The open gate approach provides options for creating a shifting habitat mosaic without relying on regular prescribed fire.

I don’t have many years of experience with this open gate approach, or much data to help me understand all the nuances of its impacts on flora and fauna.  However, what I’ve seen from early experiments seems promising.  I’m sharing the idea and our experiences so far, not because I’m endorsing the open gate approach as the next big thing, but because I hope others might find ways to try it and report back.  Because the basic idea is as simple as not closing a gate when opening a new paddock, it can be employed in many different scenarios if people see potential for it.  Also, I’m not trying to claim or patent the idea, and I’d be shocked if there aren’t people reading this that have already tried it in various forms.  If so, I’d love to hear about it.