Since spring weather has not yet touched down in Saskatchewan and there could be more snow to come, producers can look forward to seeding yet again into wet and possibly saturated soils.
Some challenges when faced with a wet spring include poor and delayed germination because of cool soil temperatures, shallow root system development that can interfere with both nutrient uptake and accessing moisture later in the season and, if flooding occurs after plant development, plants will drown due to lack of oxygen. Long term effects of excess soil moisture are mostly dependent on the soil texture. Soils with higher clay content hold moisture and are more adversely impacted than those of lighter texture where moisture can drain, such as loamy or sandy soils.
Best management practices (BMPs) are those science-based production practices that are sustainable in the long term while being environmentally sound and economically viable. These BMPs can be used to mitigate the impacts of managing wet soils.
Following are several impacts on soil and plant growth that can occur due to excess moisture along with a BMP that can mitigate effects:
Compaction. This is usually due to pressure exerted by farm equipment and can impede root growth and prevent the movement of moisture and air through the soil. A BMP to prevent this is patience, that is, wait for soil to dry out before taking equipment onto the land.
Reduce Nutrient Availability. Saturated soils are more likely to show losses of nitrogen through both increased volatilization and mineralization, releasing nitrogen gas, nitrous oxide (a greenhouse gas) and ammonia. Reduced numbers of beneficial microorganisms can also interfere with phosphorous uptake. A BMP is to follow the 4Rs for optimizing fertilization: the Right Rate of the Right Source at the Right Time in the Right Place.
Pests. Weeds, disease and insects will all take advantage of stunted crop growth and change in the microclimate of a field. BMPs would include practicing integrated pest management through careful planning and observation of field conditions and using a cover crop to break any pest cycles.
Crusting. This can happen when the soil surface dries and soil structure breaks down to prevent penetration of water and air. BMPs would be the use of a cover crop and retention of crop residue.
Pasture Damage. When grazing is allowed on wet soils, compaction from animal movement can occur and outbreaks of anthrax are common (bacteria can survive many years and thrives in alkaline conditions). The BMP for this is to delay grazing until the soil dries out and consider re-seeding for more severe damage.
Erosion and Runoff. When this occurs, there is downstream depositing of sediments and the development of gullies. BMPs for reducing erosion are mostly well-known and include grassed waterways, reduced tillage and cover crops, among others.
Salinity. Salts in lower soil regions can dissolve and rise to the surface where they interfere with crop development. BMPs would be to select salt-tolerant species and use a cover crop.
In general, a BMP that is useful for mitigating impacts that can occur on wet soils is the use of a cover crop. Cover crops can be spring cereals that are cheap to seed or fall seeded crops such as fall rye or winter wheat. Pulse crops also make an attractive alternative because of their nitrogen fixing ability. Cover crops are usually left in the field to decompose, adding back nutrients, and can break disease and other pest cycles.
For more information on this or other crops related information, contact Joanne Kowalski, Regional Crops Specialist at 306-953-2362 or the Agriculture Knowledge Centre at 1-866-457-2377.
Source: Managing Wet Soils. Agriculture and Agri-Food Canada publication.
