So, let’s take a look at the stages of growth for most forage plant species:
GRASS GROWTH — STAGE ONE
Stage one is what we’re used to seeing in early spring, as seen in Figure 2, or in many continuously grazed pastures. The pastures are greening up, yet we see very little growth for quite a long time. When pastures are grazed severely, grass growth also needs to start from stage one.
This can really slow down recovery time for the grass requiring a long rest before the next grazing. When we get thinking about this, it becomes quite obvious that pasture productivity is seriously reduced by keeping pastures in stage one.
We see a lot of pastures allowed to grow well into Stage Two before grazing begins in spring but then they are kept in Stage One by continuous grazing or long grazing durations throughout the rest of the grazing season. Any time you drive by a pasture where you can easily see the dung piles or pebbles on the ground during the growing season, you’re looking at Stage One growth. In April and into early May this is normal. In late May, June, July, August or September, for most Canadian pastures, this is not a good thing.
Stage One growth is very slow because the grass plant’s ‘solar panel’ is very small. As a result, the photosynthesis process is minimal so plants are dependent on what reserves they have stored up. Forage plants with little reserve energy will be especially slow to recover. The roots are also small at this stage, so accessing water and nutrients is limited.
Forage plants are at their weakest in stage one, and are particularly vulnerable to damage by grazing. The quality and palatability of stage one plants are high, attracting grazing animals to select these plants. If most of the plants’ energy is in the new growing shoots, and they`re grazed off, there`s just not much left to get the plant restarted.
GRASS GROWTH — STAGE TWO
In Stage Two, photosynthesis is high and as a result growth is rapid and the forage plant’s reserves are being rebuilt. We often find that, in late spring or early summer, the growth rate is so rapid that we have “trouble keeping up with the growth”. Figure 3 shows the balance of lush growth with a large root system. I think we put too much emphasis on keeping up with pasture growth. We run the risk of over-grazing by trying to keep ahead of the grass. We should always allow grasses to, at least, grow to late Stage Two, just prior to the beginning of heading.
Forages in Stage Two are of high quality and there`s lots of it. Palatability is usually very good throughout Stage Two. Timing grazing for late Stage Two offers the best balance between quality and quantity of forages on our pastures. The class of livestock to be grazed and their desired level of performance will help us determine whether to graze earlier in Stage Two or later in Stage Three.
GRASS GROWTH — STAGE THREE
The beginning of Stage Three is the beginning of flowering and heading as seen in Figure 4. The plant’s energy reserves are rebuilt and energy is being directed towards flowering, heading and seed development. Photosynthesis is slowing down as the plant’s green leaves are reduced. Forage plants are safe to be grazed, even severely, in Stage Three without causing long term damage. As long as the plants have enough time to fully recover, they will be healthy and even increase in vigor and productivity.
I’ve heard quite a lot of talk about grasses heading out early and small. I’ve noted that as long as the forage density is low and some bare ground can be seen, many grasses are compelled to reproduce. When we add heat and drought stresses, plants go into survival mode. It’s as if the plants say “If I’m going to die of heat or thirst, I’ll at least make sure I’ve left offspring to grow next year”. I’ve found that pastures with very dense, leafy forage populations of healthy plants tend to be much slower to head out.
Forage quality is declining in Stage Three and you’ve pretty much maxed out the volume of forage available from that growth cycle. I’ve always found there to be plenty of nutritional quality in Stage Three forages for horses, or for cow/ calf production as long as there’s always enough forage there to keep them full.
You can read the whole article in the June/July 2013 issue of Canadian Cowboy Country magazine.
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