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Let’s take a walk

Woody Lane, Ph.D., for Progressive Forage Published on 31 May 2019
Pasture walk

Come … join me for a pasture walk.

I know you’ve already walked through lots of pastures, many times, but a formal pasture walk is different.

We won’t just cross fields to watch animals or chase them; instead, we’ll walk slowly, focusing on the forages, not the livestock. We’ll look at the pasture from a grazier’s perspective.

We’ll consider that our real crop is sunlight, that our forages are the photosynthetic machinery that harvests the sunlight, and that our animals are the sunlight products we sell in the market. You won’t be bored. If you’ve never done a real pasture walk, there’s quite a lot to see. And it won’t take long; I’ll get you back in time for the next page. Oh yes, grab yourself a pair of rubber boots; it’s wet out there.

Let’s start with this grazed field behind the barn. It’s about 10 acres with a border of trees and a stream at the far end. Notice that there are no cross-fences. The owner told me he pulled his animals off 14 days ago, so we are looking at two weeks of regrowth. Hmm. Not very much, even though we’ve had good weather lately with some rain. Let’s come back to this item in a few minutes.

Look at the color of the grass. It’s a bright, light green. Looks nice, eh? To some folks that would be beautiful, but not to me. What does that color really tell us? As you look around the field, you’ll see lots of patches of darker green with taller growth. Look carefully at those patches; their forage is deep green and very dense. It’s obvious that each square inch in these patches contains far more leaf area than the surrounding ground. Leaf area means more sunlight captured and more feed for our animals.

Well, those deep-green patches are manure or urine patches, and they tell me the field is low in nitrogen or phosphorus. Manure contains nitrogen and phosphorus; urine contains nitrogen in the form of urea. Those taller plants are getting enough nutrients to support a fast regrowth, while the surrounding plants are not. In practical terms, a slow regrowth translates to a longer waiting period before livestock can go back into the field.

Before we started, the farmer told me he has spread manure on this field for years, and last fall he had also applied 60 pounds of urea fertilizer. That’s 60 pounds of fertilizer per acre. Urea is only 46 percent nitrogen. (The label on the bag lists “46-0-0-0.”) Therefore, those 60 pounds of fertilizer really equate to only 28 pounds of nitrogen per acre.

Frankly, that’s not very much nitrogen. Also, urea is quite soluble and, in this region, this form of nitrogen is only effective for approximately 60 days. That’s why the grass was light green; in spite of the manure applications, it is still starved for nitrogen.

Here’s a story: Last year on a different farm, as we stood in a field that looked just like this one (light green with very little growth), I noticed a large, deep-green area about 30 yards away. It really stood out; its grass was at least 6 inches higher than the surrounding area.

But the patch was a full 6 feet across, much too wide for a manure patch. I joked with the farmer, “Did a ewe die there?” He didn’t remember, so we all walked over and examined the forage. And found bones. Yes, I suppose this does add a new dimension to the term “fertile ewe,” but I wouldn’t recommend it as a routine fertilizer practice.

Let’s come back to our paddock. Notice that the total pasture mass is quite low. I’d say it’s only around 1,000 pounds (of dry matter) per acre. This is after 14 days of recovery. There is a problem here. Normally, I would remove animals from a pasture before they grazed the residual down to 1,000 pounds. This pasture is telling me the animals had been left in too long during the last grazing period. They had probably grazed it down to 700 pounds or even less. That’s well down into Phase I growth.

Plants in this part of their growth curve require a long recovery period until they have enough leaf area to capture enough sunlight for higher rates of growth. And this is early summer – we should be seeing an incredible surge of growth at this time – yet this forage is hardly growing. Fourteen days of regrowth has resulted in only 300 pounds of dry matter, a growth rate of only 21 pounds per day.

I would expect that forage like this, if it was in Phase II growth, at this time of year with good weather and fertility, could grow at a rate of more than 100 pounds per day. This field, however, is being forced to struggle back from Phase I without good fertility. Think of all of the sunlight not captured.

There are, however, more efficient alternatives. During periods of high growth rates, some good graziers routinely expect to rotate animals through their paddocks every 17 to 21 days. But those graziers maintain high soil fertility, and they leave a lot more residual forage in their paddocks, which gives plants a running start for their next growth cycle. Those graziers can’t afford the long lag period from Phase I plants. Look at this field here: After 14 days, it’s just beginning to add enough leaf area to support good growth. It will be another 20 days before this farmer can properly put stock back on it. So instead of coming back to this field in 21 days, animals won’t return here for at least 34 days.

One last thing – look over there, near the stream. See those large areas of tall grass that resemble bamboo? That’s reed canarygrass (Phalaris arundinacea). It likes to grow in wet areas. Reed canarygrass may be an invasive volunteer species farmers hate, but it’s clearly growing in its niche on this farm. Since no one planted it, it must be one of the older, less palatable varieties.

Those plants are tall because the animals didn’t want to graze them. That tells me the stocking density was too low in this paddock or at least in that area of the paddock. The animals refused the reed canarygrass because they had the luxury of alternative feeds. There was no cross-fencing, so the stock could avoid these reed canarygrass areas even as they contentedly overgrazed other parts of the field.

I know most folks curse reed canarygrass, but look at that growth. Maybe the reed canarygrass is telling us something. Maybe that area should not be treated like the rest of the field. If this were my place, I would probably fence that area as a separate small field so my animals would have no choice of feeds, and I’d move stock in and out as often as necessary to keep the plants low and nutritious. Otherwise, all that incredible growth of reed canarygrass simply means a lot of photosynthesis is going to waste.

Well, it’s time to go. Please close the gate on your way out. Let’s do this again soon – we’ll walk through a different paddock. And next time, I’ll make sure the electric fence is off.  end mark

ILLUSTRATION: Illustration by Ray Merritt.

Woody Lane is a certified forage and grassland professional with AFGC and teaches forage, grazing and nutrition courses in Oregon, with an affiliate appointment with the Crop and Soil Science Department at Oregon State. His book, From The Feed Trough: Essays and Insights on Livestock Nutrition in a Complex World, is available through Woody Lane.

Woody Lane, Ph.D.
  • Woody Lane, Ph.D.

  • Lane Livestock Services
  • Roseburg, Oregon