Seed bed: What grade do you get on your cropping report card?

Wednesday, November 4, 2009

Understanding how your yield compares and what factors affected it can help you plan for next year

by KEITH REID

Unlike school, where the students get their final report card in June, farmers get their grades in the fall when the crop is harvested. This is an excellent time to assess your soil and nutrient management program, and to plan for any changes that need to be made for next season.

The challenge is that, while differences in yield are obvious, the factors that caused those differences may not be. We also have to keep in mind the weather conditions of the past year, which will have influenced the crop's response to management. It is always a balancing act between making changes that will improve crop productivity for years to come, and responding to specific conditions in the past season that may never be repeated again.

How did your yield compare to that of the neighbours? By this, I do not mean, "Did you get top bragging rights at the coffee shop?" The coffee shop is notoriously unreliable, since you only hear about the best yields in a good year and the worst yields in a poor year.

You should, however, be aware of the general yield trends in your area. Slightly below average yield from your fields while everyone else is down 20 per cent should tell you that your management was on track to deal with the conditions this year. If the opposite is true, with depressed yields on your farm while everyone else was near average, it suggests you need to look closely at your management decisions.

What factors had the biggest impact on yield this year? Once you know where you sit relative to local yield trends, you can start to make judgments about factors affecting yield results. Some will be obvious, like early frost, hail damage or weed escapes. The challenge comes in sorting out the less obvious factors.

Nutrient deficiencies often manifest themselves as "hidden hunger," where there are no visible symptoms on the plant but yields are reduced. Post-harvest soil samples will confirm if your fertilizer program was adequate for this year's crop and aid in planning for next year. They will also identify other chemical limitations, such as low soil pH.  Soil compaction or poor soil structure will not show up on a soil test, but can have just as big an impact on crop productivity by limiting the ability of roots to reach water and nutrients.

The next step is to consider interactions between these various factors.

Did the plants suffer from low nitrogen because of inadequate supply in the soil, or because compacted soil prevented the roots from reaching the available nitrogen? Was poor standability due to genetics, or to stalk diseases exacerbated by low potassium?

If you get discouraged by the range of possibilities, a Certified Crop Advisor is a good resource to help you sort out what might be going on.

Did you spend too much for your yield?
At harvest time, we focus on the bushels per acre, but economically (and environmentally) it is just as important to look at how expensive it was to grow those bushels. Are you fertilizing for more yield than the field is capable of producing? Have you been making "insurance" applications of micronutrients that are not really necessary? Is your tillage program creating optimum soil conditions with the minimum number of passes, or are you spending more on diesel fuel than is really necessary?

Understanding these costs, and knowing whether they have contributed significantly to yield or not, will help you to maximize your bottom line. BF

Keith Reid is soil fertility specialist with the Ontario Ministry of Agriculture Food and Rural Affairs based in Stratford. Email: keith.reid@ontario.ca