Grazing on Wet Soils

Q: I was in conversation with a California rancher who has his herd out in the winter when the grasses grow in that Mediterranean climate. With the winters come the rains which make the clay soils wet and the herd compacts the soil. We know that compaction reduces water infiltration. Does anyone have experience with being able to reduce that type of grazing compaction given the dominance of annual grasses in that climate? Any strategies to suggest? The grazing goal is to increase perennials and improve bird habitat and to have a profitable livestock operation.

A: I have found that less compaction happens when there is maximum diversity of plant types and covered soils and when you use different types of grazers with less pounds per square inch with each hoof. If possible, identify those areas with soils that are most likely to compact and plan to graze them before the rain events start. Historically, we don’t know when that will occur, but the beauty of the flexibility of holistic grazing planning is that we can replan when needed.

—Rob Rutherford

A: Even on the North Coast where winter rain is quite abundant, it tends to come in discreet, forecasted storms with dry periods between them. I graze sheep on level alluvial clayey soil. Water will stand on the surface during and shortly after a storm but will infiltrate within a few hours, even on compacted areas like lanes, when the rain stops. It doesn’t puddle up where there is good grass and litter cover. Also, I keep the animals in the barn during the worst of the downpours. I think these observations confirm what Rob is saying about timing grazing to avoid a lot of hooves on the wettest areas during the wettest weeks, and keeping soil well covered. All the cool season grasses, annuals and perennials, do best with fall seeding. Over-seeding perennials like orchard grass or clover ahead of grazing and rain events might work? Spreading barn litter on areas with poor grass cover has helped my pastures, but I’m dealing with very small areas so that might not be practical for a larger operation.

—Rhoby Cook

A: New Zealand West Coast dairy farmers only allow their stock on pasture for no more than three hours, probably less depending on how quickly they achieve gut fill. Pugging occurs after that stage as they wander around trying to find a dry spot to lie down and ruminate. They are often taken to a feed pad or barn between grazing. A sacrifice paddock means you are transferring fertility.

Another thing to consider is how you organize your winter grazing planning. I have client here who add to their winter recovery period an extra 15% of days to cover breakouts, water problems, and wet weather, similar to the drought reserve you’ll practice with Holistic Grazing Planning. It means during wet periods you have flexibility to move livestock faster. You can always come back once the frosts strike.

Research here also implies strongly that higher post-grazing residuals—in excess of 1,760 lbs DM/acre (2,000 kg DM/ha), has a greater influence on reducing pugging than livestock liveweight, but like the majority of livestock research that has a caveat around mob size as the research was completed with mobs of 20 cattle. Residuals at that biomass will provide plenty of cover for bird nests.

—John King

A: Living here east of the Mississippi and pretty far north (Wisconsin), we have what we call ‘mud season’: the annual time starting when the ground goes from frozen (we call it ‘free concrete’) until the lush growth of summer. There are also periodic times during the growing season when high rainfall can result in a mini-mud season. Here are some observations from our experience:

1. Grazing lightly (leaving more residual) and moving frequently reduces serious sward damage and pugging. This is not a time to do mob grazing!

2. We’ve found that if the grazing is of short duration and lower stocking density, any compaction you have (at least in our climate) is pretty short lived--some studies have shown that it is gone by the end of the next recovery period.

3. If there is compaction, it is usually pretty shallow and you could consider planting species with deep tap roots that can punch through the compacted layer (alfalfa, chicory, and there are probably native species).

4. Designate a ‘sacrifice paddock’ for wet periods. Once the wet period is over, you move the herd back onto the rested paddocks and renovate the sacrifice paddock. This renovation process is a way of introducing more seed to the pasture, maybe more durable species, and thickening the stand which can reduce the problem in the future.

5. Some farmers in this area, especially dairy graziers, invest in a concrete feeding pad to use during wet periods and winters.

—Laura Paine

A: We also have a lot of experience with wet winters and danger of pugging. I agree with a lot of what has been said, but not the sacrifice, pads etc. With high landscape function (> 30% perennial grass basal area [>4cm2 ] and decomposing litter in the intertussock space) produced from the following practices you can reduce concerns of pugging:

• Long recoveries of approximately 12 months (Gabe Brown suggests even longer up to 15 months—with even six months for wet, humid areas),

• High stock density > 400 cows/acre (1,000 cows/ha), and

• High utilization >70% (we shift the animals slightly quicker through more moves per day not bigger areas).

The photo on page 15 is during a 12-inch (300 mm) rainfall on a flat creek. The next strip is ready to go and animals look like they have to step up into the grassland.

Please do a safe to fail trial before thinking why this would not work on your land. This management is very inconvenient and requires adapted animals.

—Graeme Hand

A: There is a wide range of quality on California’s annual grasslands. I have been on some where grass was sparse even in the best of seasons and others where the sward was really, really thick. Depending on prior management, you may need a transition period to get to healthy, thick swards, and you may consider changing type of livestock or class of livestock or season of use. It is important the grasses have a chance to set seed in the spring. Many operations keep their cattle on the dryland until they get the first cutting of hay off the irrigated land, which in many places, means the dryland grasses are severely grubbed and the soil moisture is too low to allow the grasses to regrow and set seed.

With this in mind, you may also consider the stocking rate to determine if you have too many animals to allow the proper rest at the most critical times of year so the desired species can set seed.

—Angela Boudro

A: I don’t have any moist soils that don’t compact from livestock (or vehicles or my footprints) on my small ranch, and I think compaction in various degrees is present on all my soil types when I compare with areas cattle don’t step on.

Here’s what I know about the extensive areas of heavy black clay (high shrink-swell) here on my small ranch in northern California and their relationship to livestock and wetness. I’ve found the excessive damage occurs only when the herd is on too long while it is raining and the upper soil profile is fully saturated. By excessive damage, I mean killing annual plants from the serious deep pugging rather than just compaction. Once that upper part of the profile has a chance to drain, cattle no longer are doing the extensive damage.

I don’t have any significant cover of perennials on the majority of my clay soil acreage. Where I do have small patches of robust perennials, pugging is not an issue; excessive damage or compaction is of no concern due to the strength of the root mass.

I have come to believe it is the soil macro-pores (within and between the big clay clods that shrink-swell) that are fully saturated before the serious pugging damage to plants/soils occurs. My fields with clay soil are dominated by annual grasses/forbs. I remove the herd from such paddocks as soon as I see severe pugging is occurring, which only occurs with prolonged rains. I simply move the herd into a paddock with loamy soil that is not the plastic clay. It usually takes only a day (two at most) after the rain stops and I can safely put the herd back into that clay paddock, even if on relatively flat terrain with a few puddles. My experience is that the internal soil drainage provides a much firmer footing for cattle. It happens much more quickly than I would have expected on my place, even on flat terrain, after the rain stops

When doing the grazing planning, this can be a very important issue when the number of paddocks available shrinks, particularly in wetter years if/when the “available paddocks” shrinks for a considerable amount of time and will affect grazing and recovery periods for the other paddocks. We can also calculate two different sets of grazing periods to guide us in dry and wet years when doing the planning chart work for the upcoming growing season. That helps keep us on track with the planned recovery for all the paddocks in both wet and dry years.

Thirty years ago, I put cattle onto my paddocks after the area had been farmed (plowed, disced, harrowed) year after year by my previous generations to raise oat/ryegrass/vetch hay. I could not avoid serious pugging on any soil type. I think that was because annual tillage provided better macro-pores to the depth of tillage (except at the soil surface where light capping would quickly develop when the rains began). Cattle legs could easily sink into any fully saturated soil that was tilled the year before. But because I stopped all tillage and managed for plant vigor of all the annual volunteer species (annuals), their seed production and soil cover, such pugging damage quickly disappeared and only happens now on the clay soils with the prolonged rains (and lack of good perennial sod). The pugging damage on other soils, which are loamy soils that are much less plastic, is far less even when they are fully saturated.

I haven’t been concerned about stock density and timing on my place, except when the herd crowds a paddock corner or fence line during prolonged windy rainstorms while soils are fully saturated. But those are very small areas. With a very large herd, that could be a very large area. I find these occasional sore spots add plant diversity in various directions, and they are almost like a small unplanned ‘safe to fail’ trial because they can happen anytime during the months of winter’s slow growth. How that very small site responds to excessive pugging damage can be quite variable because of timing, amount of litter, and size/amount of perennials if present. And I’ve learned monitoring is key to learn what these unplanned trials are telling me about the ecosystem process changes after extensive pugging and about recovery period needs.

Another trial I conduct and watch carefully is a small paddock in which I ‘rest’ year after year. I’m curious about how the brittleness in my area affects the kind of speed of successional change on different soil types and in comparison to planned grazing; and I do it so that people who want to visit my place can see a significant area that receives no grazing. Soil compaction appears to have fully recovered in the top foot after many years, but the paddock has become an annual weed patch. No soil compaction, but energy flow is very minimal during the winter months because of the poor biological litter decay and excessive litter. I do see a few more perennial grasses slowly ‘invading’ this over-rested paddock than I see on the adjacent grazed paddocks, but that may be because of the prevailing wind direction from on old fence where birds drop seed, or because the paddock excluded from grazing hadn’t been farmed every year by my family. Soil microbiology may be quite different from adjacent paddocks that were farmed since my great grandfather’s day or more.

—Richard King