Winter changes many things on a rural property. The animals' routine, feed consumption, pasture management. But there's one point that few producers consider with the attention it deserves: what the cold does to the manure lagoon.
In southern Brazil, where winter temperatures can drop below 5°C for extended periods, the manure lagoon behaves differently. The substrate becomes more viscous, biological decomposition slows down, the crust hardens, and pumping becomes more difficult. All this while the volume of manure generated by the herd remains the same or increases, depending on the farming system.
In this article, we explain what changes in the behavior of the pond during winter, what the risks are during this period, and why monitoring is even more important at this time of year.
What does the cold do to the sewage lagoon?
The waste lagoon is a living biological system. What happens inside it depends largely on the temperature. And when the cold arrives, this system reacts.
The substrate becomes more viscous.
As temperatures drop, the viscosity of the waste increases. The material becomes denser, more resistant to movement, which means the lagoon needs more energy to be homogenized. An agitator that works well in the summer may have difficulty moving the same volume in the winter.
Biological decomposition slows down
The bacteria responsible for decomposing organic matter are sensitive to temperature. Below 15°C, biological activity drops significantly. This means that the substrate decomposes more slowly, and the volume of material in the pond grows faster than in summer.
The crust hardens.
In cold weather, the crust that forms on the surface of the pond hardens more quickly and becomes thicker and more compact. A hardened crust is much more difficult to break than the typical summer crust, and requires more agitator power to break it.
Pumping becomes more difficult.
The combination of a more viscous substrate and a thicker crust makes pumping more difficult in winter. The pump needs to work harder to remove the same volume of material, and if the pond is not well agitated, what comes out is the more diluted surface layer, which has less agronomic value.
Specific winter risks for the lagoon
Winter brings together a set of conditions that increase the risk of problems in the lagoon:
Accelerated volume buildup
With slower biological decomposition, organic material accumulates more quickly. If the interval between pumping sessions is not adjusted to this reality, the lagoon may reach its limit sooner than expected, precisely when pumping is most difficult.
More compacted sediment
The cold weather promotes the compaction of sediment at the bottom of the lagoon. Material that would still be partially suspended in the summer settles and compacts in the winter, reducing the usable volume of the lagoon and hindering homogenization.
Rainy season
In much of southern Brazil, winter coincides with periods of higher rainfall. Rain increases the volume of water entering the lagoon, especially in uncovered systems, further accelerating the filling process.
Difficulty of application in the field
Soil saturated by winter rains does not absorb biofertilizer properly. This limits pumping periods and requires more careful planning to avoid creating environmental liabilities.
Why agitation is even more important in winter
While activity is essential in the summer to keep the lagoon functioning well, it becomes critical in the winter. And for reasons specific to that time of year.
To break the hardened crust
The winter crust is thicker and harder. Without sufficient agitation, it is not broken and continues to grow, trapping gases and reducing the active area of the lagoon. The agitator needs to have adequate power and length to break up this layer and put the material into suspension.
To maintain substrate homogeneity despite higher viscosity.
A more viscous substrate resists movement more. Agitation needs to be more intense and more frequent in winter to ensure the same level of homogenization that would be achieved with less effort in summer.
To facilitate pumping during available periods.
Since pumping opportunities are more limited in winter due to waterlogged soil, low temperatures, and adverse weather conditions, every pumping opportunity needs to be well utilized. And this utilization begins with a well-stirred pond and a homogeneous substrate.
To prevent the lagoon from reaching its limit.
With the volume increasing faster and pumping opportunities becoming scarcer, the lagoon needs to be constantly ready for pumping. Regular agitation ensures that, when the time is right, the material is ready to be pumped out.
What adjustments to make in winter management
Managing the lagoon in winter doesn't need to be radically different, but it does need to be more attentive.
Some adjustments make a difference:
Increase the frequency of shaking.
In summer, weekly stirring may be sufficient to keep the pond in good condition. In winter, the increased viscosity and faster crust formation require more frequent stirring, at least twice a week in ponds with larger volumes or denser substrate.
The programmable electric stirrer has a clear advantage here: it can be configured to operate more frequently in winter without requiring manual intervention each time it is activated.
Shake for longer before pumping.
With a more viscous substrate, the time required to homogenize the pond before pumping increases. In summer, 2 hours may be sufficient. In winter, depending on conditions, it may be necessary to stir for 4 to 6 hours before starting pumping to ensure that the material is truly homogeneous.
Monitor the lagoon's water level more closely.
With the volume increasing more rapidly, the interval between pond level checks should be shorter in winter. A well-defined warning point, a visual marker or ruler allows the producer to plan pumping in advance, without relying on urgency.
Take advantage of windows of favorable weather.
In winter, days with milder weather and soil with good absorption capacity are rarer. When they do appear, they need to be taken advantage of. A well-watered pond and homogeneous substrate ensure that pumping can be done efficiently when the window of opportunity arises.
Check the agitator maintenance before winter.
Winter is the time when the agitator will work harder with more resistant substrate and for longer periods. A preventive inspection before the arrival of the cold weather, checking seals, bearings, propeller, and motor, avoids breakdowns at the worst possible time.
A well-managed winter means a lagoon under control.
Winter doesn't have to mean problems for your manure lagoon. By paying attention to changes in substrate behavior and making simple adjustments to your management routine, especially in the frequency and duration of agitation, it's possible to keep the lagoon functioning well even in the most adverse conditions.
The producer who understands what cold weather does to the pond acts before the problem appears. And the right agitator, operating at the right frequency, is what makes this possible.
A lagoon that's very busy in winter is a lagoon that doesn't charge high prices at the wrong time.
Do you want to make sure your pond is prepared for winter?
AGTO manufactures tractor-driven and electric agitators for swine and bovine manure lagoons, with models for different volumes, depths, and substrate types. Our technical team analyzes the characteristics of your lagoon and recommends the right equipment to maintain efficient management at any time of year.
Get in touch and speak with an AGTO specialist.
