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Keeping soil biology ticking

Pasture Management: Grazing setbacks happen, but find opportunities to get back on track

Normal weather” at 4 Clover Ranch near Rocky Mountain House, Alta. has been illusive for a couple of years at least and it has created some grazing challenges at the expense of pasture performance.

Our planned grazing system, where we look at the health of the grass on an ongoing basis, has responded well over the 25-year journey. I have written other articles about our grazing data collection and observations of pasture health in relationship to the way we graze our paddocks. It has been a rewarding experience.

It was an extraordinary observation a couple of years ago to have the “ah ha moment” of discovering improving mineral cycling in the soil and the effects of mycorrhizal fungi assisting with the creation of a strong environment for soil micro-organisms. It frees up soil nutrients that wouldn’t be plant available otherwise. It is especially relevant since we don’t use any form of commercial fertilizer. It is good to see plant species composition across all paddocks have steadily increased as a result of our grazing system.

However, the last two years of bizarre weather patterns, extremely low winter precipitation, below-average snow cover, early-season droughts and slow pasture growth in spring really challenged the soil biology processes that had kicked into gear so nicely.

In addition to the poorer pasture performance, accepting more cattle for our grazing operation compounded the issue as we couldn’t leave sufficient litter in the paddocks to feed the soil fungi. We paid for those decisions but things are looking up.

Pastures recovering

In west-central Alberta last season we received an abundance of rain from early July, totalling over 22 inches by October. Although the pastures were extremely slow to get started there was soon some recovery and the second pass in our planned grazing system saw great stands of high-quality feed.

Early in the spring we noticed that the urine and manure spots were showing across the paddocks, where they weren’t seen before, a sign of poor nutrient cycling. In September, to our delight, as the cattle were well into the second rotation, these spots were gone suggesting with the additional soil cover from the forage stand there was renewed activity in the soil — fungal activity was kicking in again. Soil micro-organisms such as bacteria, nematodes, protozoa and amoeba were all busy exchanging favors with the fungal mycelium and plants responding with healthy growth.

With the relatively poor outlook in the spring we had backed off the 2016 stocking rate slightly, with 62 cow-calf pairs and three bulls for the home quarter and 42 cows and calves and two bulls on the east quarter. We had announced a couple of options for the clients we custom graze for — early exit or destocking by late summer.

As a result, the home quarter herd left early and by fall we were down to 32 pairs and one bull on the east quarter, leaving a great scenario of plenty of carry-over that will sustain a healthy soil biology and allow for recovery from the two years of grazing above a level we felt was sustainable.

We keep close tabs on grazing data on an annual basis and with these adjustments we are aiming at a stocking rate of roughly 10,800 Animal Unit Days (grazing days) for the season on the home quarter and 6,100 AUD on the east quarter. This should prevent the setbacks we saw in pasture health the last couple of years. Leaving litter is crucially important to maintain heathy soils and an active soil biology so fundamental to pasture productivity. It takes years to build a healthy soil function and we sadly discovered how quickly it can deteriorate.

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