Making sure the bad crop years don't hurt as much

Tuesday, November 1, 2011

We can never overcome all the impacts of adverse weather, but good soil management will keep the yield hit to a minimum

by KEITH REID


The trouble with following an excellent year for growing crops, like 2010, is dealing with the disappointment when this year's crops don't measure up to our expectations. The hurt is especially sharp when crop prices are at historic highs.

As you look up and down the concession, however, it is easy to see that, while everyone suffered with the challenging weather in 2011, not everyone suffered equally. Was it just luck? Or is there something you can do to make sure you are in the "lucky" group the next time the weather turns against you?

The key to growing good crops in tough years lies in your soil. A resilient soil can handle a moderate amount of traffic or tillage when it is a bit on the wet side, without forming hard clods. The pore space will allow excess moisture to drain away easily and let air into the soil, while holding on to the moisture that plants can use.

The same pore space will allow roots to grow easily through the soil, so the crop can pull water and nutrients from a large volume of soil. Soil in this condition is less likely to impede crop emergence through crusting or limit root growth by side-wall smearing of the planting trench than a soil in poor condition. The moisture-holding capacity and large root systems also prevent moisture stress during dry periods in the summer. All of these factors add up to improved yields at the end of the year under less-than-ideal weather conditions. 

Some of the differences in how a crop responds to weather conditions stem from differences in soil texture and where the field sits in the landscape, factors that you cannot change.

That doesn't mean that management won't make a difference on the loamy soils, but it does mean that it will make a bigger difference on soils at either the fine or the coarse extremes of texture. I recall, as a boy, the local ag rep telling a neighbour that "a farmer only has to know enough to put seed in the ground to grow crops on that good soil, but you have to know how to farm to be successful on your tough clay."

Building a resilient soil means looking beyond this year's crop and farming for the long term. The exact mix of practices will need to be tailored to your own farm situation, but there will be big benefits in finding ways to apply as many of these as you can.

n  Practice crop rotation. The advantages in changing crops each year go beyond avoiding the build-up of insects or diseases. Plant roots will follow the old root channels from a different crop, but avoid root channels from the same crop, so rotated crops will have larger root systems. Even better, add perennial forages into the rotation to establish deep root channels, build soil structure and add soil organic matter. 

n  Build soil organic matter. This is the glue that holds soil structure together, while acting as a sponge to improve water holding capacity. It is also the food source for all the biological activity that is so important for a properly functioning soil. The trouble is that organic matter is much easier to lose than it is to build, so you need to take every opportunity to add organic matter to your soil as crop residues, added manure or compost, or by growing cover crops. On the other side of the equation, avoid excess tillage that burns up organic matter.

n  Keep soil in place. When soil erodes with wind or water, the part that is lost is higher in nutrients and organic matter than the bulk soil, so the impact is much greater than just the tons lost. Keep the ground covered with growing crops or crop residue, and minimize the amount of tillage to reduce soil erosion.

n  Manage soil water. Adequate drainage increases the depth of the rooting zone, so it actually increases the amount of available water for crops. It also reduces the chances that you will be driving over a soil when it is too wet and so prevents soil compaction and structural damage.

n  Minimize compaction. Soils with the pores squeezed shut will not drain easily or allow vigorous root growth. Minimize trips over the field, keep axle weights and tire pressures low, and stay off the soil when it is moist. Even better, if you can manage it, is controlled traffic where the damaging effects of compaction are limited to a very small part of the field.

We can never overcome all the impacts of adverse weather, but good soil management will keep the yield hit to a minimum and allow you to take advantage of the good crop prices that usually go along with a tough year. BF

Keith Reid is Manager (Eastern Canada), Soil Nutrient and GHG Management, Agriculture and Agri-Food Canada, Guelph.