Weathering the weather in Atlantic Canada
The consequences of changing precipitation regimes on soil conditions are numerous. What are some ways to mitigate them?
April 19, 2023 By Caitlin McCavour, Perennia
One of the many challenges the agriculture industry must face with climate change is the increase in frequency and severity of storms and changes in precipitation regimes. In the Atlantic region, spring and fall have been getting wetter and summer has been getting drier. It is making it increasingly difficult to manage water on-farm, and many producers are becoming more reliant on irrigation and artificial drainage.
The changing precipitation patterns have altered the quantity of water available to farms and the timing at which water is available. There is a growing need to build soil resiliency to adapt to changes in weather patterns. There are many consequences to poor water management, and excess water in the spring and fall can result in the following:
- Compaction from heavy traffic results in compressed soil particles and reduced pore space. It restricts root depth and can impact plant growth. The use of heavy machinery or even foot traffic on your fields when wet can cause rutting and decrease productivity in the affected areas.
- Water erosion, in which soil sediment is moved and relocated. Soil erosion can remove topsoil resulting in the loss of the most fertile part of your soil. Rills and gullies occur due to soil erosion, and these areas cannot support healthy crop growth. In extreme cases, this can prevent the use of machinery.
- Water runoff and leaching of plant-essential nutrients. Runoff occurs when water input from rainfall or other sources exceeds your soil infiltration rate. Nitrate is a plant-available form of nitrogen that is soluble in water, and can be leached (removed) from the soil through runoff. Phosphates can bind to soil particles and be lost through erosion with increased runoff. This loss of nutrients can instigate nutrient deficiencies in your crop and may require greater amounts of fertilizer to compensate for the loss. In addition, phosphates and nitrates in runoff water can cause damage to adjacent ecosystems such as freshwater streams.
- Lower oxygen in soil pores and restriction of root growth and microbial activity. Warming temperatures increase microbial activity in the spring. Oxygen in the rooting zones allows for aeration, which dries the soil and helps increase soil temperature in the spring to promote seed germination. Water in the rooting zones for long periods can delay the planting season by delaying soil warming. If water remains in your field for long periods, inhibiting planting and plant growth, surface or subsurface drainage should be considered.
- Loss of soil nitrogen through denitrification. Denitrification is the conversion of nitrate and nitrite to gaseous forms of nitrogen, like nitrous oxide. Denitrification increases when low oxygen in the soil results in nitrogen losses.
Lack of water in summer can result in the following:
- Reduced plant water uptake, resulting in drought symptoms. Irrigation may have to be considered if drought-like conditions frequently occur in your field.
- Decreased microbial activity results in decreased mineralization and lower nitrogen and phosphorus availability. Microbial activity in soil largely depends on soil moisture and soil temperature. Alterations to temperature and moisture through drought can alter soil organic matter decomposition.
- Decreased movement of nutrients through soil solution, resulting in lower nutrient uptake. Plant nutrient deficiencies often occur.
To avoid these consequences, it is important to increase water infiltration and water holding capacity. Controlling water on your farm can be difficult and expensive, but soil organic matter is one of the most important tools for water management. Soil organic matter is reported on a soil test report, and taking soil samples is vital for soil management. Soil organic matter can often be thought of as a sponge; it can absorb water and slowly release it, helping to manage both lack of and excess water.
Some practices which can help increase soil organic matter are:
- Using cover crops to promote plant rooting and help increase infiltration;
- Leaving crop residues on the field;
- Applying organic amendments such as compost and manure;
- Using a diverse crop rotation; and
- Reducing tillage.
Keep in mind that organic matter can take a long time to increase, and improvements in water dynamics may not occur immediately.
In the face of increased climate volatility, managing water on farms will become increasingly difficult. However, building soil resiliency through increased organic matter can help mitigate some of the risks of climate change.
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