Lessons from the summer drought of 2012

Tuesday, October 2, 2012

With most farms hurting, this is a good time to reflect on what happened and how to avoid it in the future

by KEITH REID

By the time you read this, the cropping season of 2012 will be pretty much done except for assessing the drought damages.  As I write in late July, however, the corn is just tasselling and the soybeans are flowering while we are in the middle of record-breaking heat and dryness with no sign of significant relief in the long-range forecast.

I don't think I'm going too far out on a limb to predict that, while most farms are hurting, some fields will take a bigger yield hit than others.  So this is a good time to reflect on what could have caused some fields, or partial fields, to suffer so badly and, more importantly, how to avoid this in the future.

Lesson 1: Good soil management can make the difference between no crop and a decent crop. It is unreasonable to expect that any level of soil management can make up for a month without rain, but it can reduce the amount of damage. We can see the fields where there has been a forage-based rotation or that have received regular additions of organic matter from manure, compost or cover crops. These fields stayed green and vigorous for two weeks or more after fields without these advantages began to show drought stress. They also bounced back more quickly after a shower, showing that the soil was able to absorb all the water that fell on it.

Lesson 2: Past mistakes can come back to haunt you many years later. Several farmers have commented to me about stunted patches in fields that normally grow evenly from front to back. Some of these "mystery patches" relate to variations in the subsoil, but more often they are evidence of the track the manure tankers took across the field or the place where the combine got stuck 10 years ago.

The negative impacts of soil compaction can last for a long time, but they only show up when there is weather stress. The best way to ensure consistent crop production is to keep compaction from happening in the first place.

Lesson 3: Crop residue on the surface is a good thing. Most of the focus on crop residue has been on its role in preventing soil erosion, but in a dry year it can also act as a mulch to slow evaporation from the soil surface and moderate soil temperatures. Both of these serve to preserve moisture in the soil so more is available to the crop.

Aside from this, crop residue on the soil surface is an indicator the ground was not excessively tilled before planting. Each tillage pass in the spring dries out the soil, and the rule of thumb is that this amounts to one-quarter inch of moisture for every pass.  Farmers who kept the trips over the field to a minimum this spring started out with more moisture in the soil to keep the crop going.

Lesson 4: Early planting pays off. In general, soil conditions were fit for corn planting by mid-April, but much of the corn didn't get in the ground until May. The later planted corn missed some rain that helped with even germination and allowed the crop to get a healthy root system established before the ground dried out, so it could pull water from deeper in the soil profile. Early-planted crops generally outperform late-planted crops, but remember that "early" means "as soon as the ground is fit." Planting into wet soil negates the benefits of early planting.

Lesson 5: You really need "all your ducks in a row" in stress years. Successful crop production is always a matter of juggling a thousand little details, but it is even more important to get them all right in a year like this. Lack of nutrients in the soil will have a much bigger impact when there is less water to carry them to the plant roots. Weed competition will hurt the crop much more since the weeds are after the same water, light and nutrients as the crop.

Even details such as uneven planting depth will hurt the crop by increasing the competition between crop plants of different sizes. Review your entire production package for any weak areas that need to be shored up. BF

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