This is a guest post by Niels Corfield, soil health, agroforestry and whole farm planning advisor, researcher and advocate.
What can we do to capitalise on rain when it comes; so we can get more forage and improve the health of our pasture and animals? I’m going to present some observations from pastures around the UK. Along with what I feel are the key opportunities available to graziers (in the West at least).
Below are 2 pics of the same spot in a permanent pasture. What is a fairly typical situation. What can we glean from them?
Firstly, and most importantly, there are clear bare patches. There could be as much as 50% bare soil, in this case.
These images are following a grazing event (in this case rotational grazing). This type of situation may well be similar to what is revealed after a hay cut, although in this case a low “sward density” maybe a more representative way to quantify the amount of bare soil, since much of the soil after a hay cut will be covered with residues (which is good but is only short term) and otherwise covered by leaves, though still open at the base — leaving space (bare soil) between the plants.
Bare patches in the pasture (as in all soils) are a weakness since it’s a place where water and carbon are lost, and soil health is declining. But they may also be an opportunity.
Ideally, there is no bare soil in pasture, it being covered by living plants, a tight/dense sward, with a closed canopy.
See here for details on recording bare soil in pasture.
Ideally these areas are covered with residues (litter or mulch). In a grazing situation, this would be the product of high stock density grazing management, where low utilisation rates leave residuals that are trampled on to the soil surface, see brief discussion on this topic in earlier article here.
A more ideal solution to this is to have a dense sward with leaves and turf tight enough that it forms a closed canopy that covers the soil surface.
We’ll focus on this second approach and see about turning this problem into a solution.
Establishing seed into existing leys or pasture is notoriously tricky. In this piece I will not focus on the nuance of this process. Except to say that when selecting methods available to you, whether through contract work or doing it your selves, those options that score higher on the soil health principles should be preferred, see above. With obviously the plough down reseeding scoring pretty low.
A few of the standard methods are outlined below:
Ensuring Good Establishment
In this case, where we have a high degree of bare soil, broadcasting is an option that is highly indicated. Basically, spinning-on a mixture of seed. Though slot seeding is still a good option, see below. Where considering broadcasting, there are a few things to bear in mind to get a good take:
1.Improve seed-to-soil contact by rolling or trampling
Cambridge rollers, cultipackers etc are suitable for this purpose as well as, grazing livestock at high stock densities — 100,000+kg live weight/ha, for a day or less (aka mob grazing) after broadcasting. Both these practices could be combined with mulching, or bale grazing, see below.
2.Retain soil moisture by covering soil
Even when there has been a lot of rain, it’s still a good idea to maintain that soil moisture, to improve the take.
Do this by spreading loose materials like straw, woodchip etc. To mulch the soil and keep the soil surface damp.
See pics below for illustration. And further discussion in mob grazing section at foot of earlier piece here.
3.Offer fodders in the field (while still moving the animals)
There’s a few different ways to cut this. But basically keeping the animals in the field and keeping them moving, ideally in tight groups, will aid the process of seed establishment. Different options include: bale grazing and green hay strewing.
Both methods mean being able to keep the animals in the field (when there’s insufficient forage left) and, particularly when combined with high stock density grazing they are ways to:
– tread-in seed — see point 1, above
– dung and urine densely — seeds will grow under pats
– provide some residues to cover seeds and retain moisture
– introduce perennial pasture seeds back into the pasture
In fact these solutions provide most of the functions required to achieve good take: seed contact, covered soil, seeds.
While also keeping animals out in the field, removing the need for muck handling in the yard. And providing better conditions for animals, than indoors.
Legume seedlings germinating in manure pile
Another option for establishing seed into pasture, perhaps where bare soil is less prevalent, and the appropriate kit is available, is slot seeding.
Drilling, rather than broadcasting means the seed will have the better seed-to-soil contact. It will also be placed below the surface where the soil moisture will be higher, at least nominally.
It is certainly more frugal with seed.
Perhaps the main drawback with this option, is that in these very dry conditions it may be difficult to penetrate the soil surface.
Either way, where the kit is available, this method is perhaps the most robust and economic — when it comes to seed, at least.
What Seeds to Sow
Making Initial Selections
We’ve talked about establishment options. So what’s the best seed to actually sow in the pasture? Given that we have run out of forage (due to a lack of regrowth) and we have a degree of dormancy in our pastures.
What might our selection criteria be for selecting plant species:
- Fast growth — forage available this season
- Bulk — lot’s of dry matter to make up for the short-fall
- Nutritious — ensuring sufficient animal performance
So, what type of plants meet these criteria?
Annuals, diverse mixes of them.
Why Annuals, What’s Wrong with Pasture Grasses etc?
Well in a word growth rate — annuals need to complete their lifecycle in a year or less (so it’s a sprint race for them), in that time they can grow tall and produce a lot of bulk and their seed is cheap. You might even have some in the shed right now.
In this case particularly, as a way to get an early bite, and to beat the season, they are highly indicated.
Coupled with that the option to use warm season species (those adapted for hot dry conditions) they’re doubly indicated.
How to get the best return on investment? Sow mixes of annuals.
Compared to this pasture species are perennials, they are: generally slower growing, slower to establish and typically much smaller plants (adapted for multiple grazing events in one season). This is all related to their life cycle of multiple year.
It’s not to say that they can’t be included in a seed mix for sowing now, but with annuals. There’s also the small consideration of seed cost. And grass seeds are on the upper end, needing to be purchased from specialists seed merchants. Another indication for hay strewing or bale grazing.
Principles of Diversity & Soil Health
One of the most important of the soil health principles is diversity. The key insight being that a diversity of plants feeds a diversity of organisms. This diversity is regarded as the key to soil organic matter formation and to a balanced diet for plants, as each organism has it’s own nutrient mineralising specialisms. Ensuring a better diet for animals.
Diversity is also correlated with increased yield.
This is where cover crops and pasture species, being mixes, really excel, compared to crops which have their own restrictions, tending to monocrops.
Once you add-in annuals into the mix, alongside perennials, you really can push the diversity lever up to 11!
Experience has also shown pasture cropping examples, like this, that have resulted in step-changes in soil aggregation, with all those extra living roots pumping-out exudates into the pasture.
Diversity in Action
When it comes to diversity, how much is enough? And what should you choose? Given there’s so much choice.
Thankfully there’s some simple rules, we have been offered from US practitioners, that we can follow:
- 8x species (or more) is a sweet spot, for soil health benefits, from
- 3 out of 4 functional groups
What are these functional groups, and why are they important?
Well they give us some pointers as well as narrowing-down the options somewhat. They are:
- Warm season grasses
- Cool season grasses
- Warm season broadleaves
- Cool season broadleaves
Perhaps this seems like an odd list. And why choose warm season plants for instance?
Well, the first reason is they can actually grow really fast. Due to the fact they photosynthesise using different frequencies of light, more prevalent in strong sun situations. This is why maize is such a high yielding crop, growing to 7′ in a season. These plants are also known as C4 plants.
The other reason we’d select them, in this particular case is due to the fact that we are actually in a warm season, right now. And our pastures (which are all cool season species) have gone dormant or “burned off” because of the extended dry spell. Warm season plants are adapted for these conditions, and have the ability to grow through the “summer slump”. Though establishment is certainly still an issue.
Below is a table of the main species of cover crops.
Remember select 8 or more species from 3 or more of the functional groups.
There’s nothing to stop you using farm-saved seed: peas, oats, wheats etc.
The other option is to source bird seed mixes and feed cereals locally/in bulk. This will certainly bring down the cost, compared to a seed merchant.
In fact there’s a real advantage to doing this as it will allow you to up the seeding rate. If there’s one golden rule with cover crop establishment it’s:
Don’t skimp on seed, too little is as bad as no seed at all.
Putting It All Together
So what might a successful oversowing of annual-based forage mixes look like?
Some examples below. And a few new bits of jargon, all of which are relevant to this situation. Although the text mostly refers to a cropping situation, they are equally suited to pasture, when due diligence is followed around establishment. It’s clear to see that these mixes have the potential to produce large volumes of diverse (quality) forage in a short space of time.
Pasture stitching is the name given to drilling forage crops into pasture.
I hope that this piece offers some practical suggestions of what to do in droughted, burnt-off pasture or more generally in tired pasture, when you want to get a forage boost, or provide forage in the off-season, while improving soil health, and with it animal health — through better quality (diverse) forage.
Take Home Messages
- Use the soil health principles to inform your decisions and to direct your observations in pasture
- Cover bare soil by litter and living plants
- Choose rapid growing annual species for instant results
- Diverse plantings are preferred, where planting date is appropriate
- Keep costs down by: using your own seed/creative sourcing
- Experiment, try some different: mixes, seed rates, establishment methods
And for those that want to find out more, or discuss this in more detail please get in touch or consider joining me on one of my soils courses. If you have any thoughts or questions, get in touch: firstname.lastname@example.org
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Part 2 — Realising the Promise of Soil Health in Organic Horticulture