SeedBed: Maxing your profits from precision farming

Tuesday, April 1, 2008

Calculating the likely benefits from using precision techniques is not always simple.
Here's what 10 years of experience tells us about the potential savings

by KEITH REID

A decade ago, precision farming was being hailed as the next great new thing, and many farmers jumped on the bandwagon. Today, the buzz has died down, or at least changed. However, it is worth looking at what we have learned over the past 10 years to see where the greatest potential exists for profit now, and in the future.

There are two ways by which precision farming could improve the bottom line - decrease the cost of inputs, or improve crop yields or quality, as long as these improvements are greater than the cost to achieve them.

To this, I add my own limitation, in that any improvement is relative to normal management rather than no management. If a grower has not been soil testing at all, and decreases his fertilizer rates in response to intensive soil sampling, part of the saving will be due to taking a soil sample at all, and the remainder the response to increased precision. Figure 1 gives an example to illustrate what I mean.

In this example, it would not be appropriate to attribute all of the savings in fertilizer cost to the grid sampling, when the grower had been applying significantly above the average requirements for the field prior to soil sampling.

This example also illustrates a challenge in measuring response to precision management. I have focused on savings in fertilizer costs, but it could be argued that the field receiving variable rates of fertilizer would give a higher yield because of extra nutrients on low testing areas.

Measuring yield responses to variable management is difficult, and so hard to quantify. An easier economic assessment is to turn it around, and look at the potential improvement in net income if we can predict input requirements more precisely. This becomes the upper limit on how much you can spend to improve precision before you are spending more than you are gaining.

The uncertainty of yield impacts also means that we can have much more confidence in our prediction of profits from techniques that save input costs with no impact on yields. The clear winners. If you are looking for a "guaranteed" return from precision farming, the only tool that fits the bill today is the parallel swath autosteer system. Overlaps of seed, fertilizer or pesticides are all direct losses to crop profitability through increased costs for the inputs. Overlaps of tillage or other field operations increase fuel consumption and equipment depreciation.

It is relatively easy to calculate the savings from reducing overlap from, say, five per cent to one per cent on all your acres. This would represent an immediate four per cent reduction in all your crop inputs (including fuel) with no reduction in yield. Dividing the cost of an auto-steer unit by the savings per acre will tell you exactly how many acres you would need to cover to pay for the machine.

The intriguing possibilities. Other precision techniques are not as cut and dried in their returns, but the potential benefits are even greater if we can overcome the technical hurdles. I put management zones and variable rate nitrogen application into this category.

Management zones are not the product of any computer program, and I doubt they ever will be. They represent the integration of a huge amount of data from yield monitors and remote sensing, modified by our knowledge of local conditions, and backed up with targeted sampling and analysis to identify yield limitations particular to those zones. Technology can assist in this process, but the most important computer for identifying management zones is sitting about two inches behind your eyes.

Variable rate N application based on crop colour is one of those concepts that should work, but doesn't yet. The challenge is being able to detect difference in greenness early enough in the season to allow nitrogen application before yield loss occurs. If the technical difficulties can be overcome, this technique could actually deliver on the promise of site-specific nitrogen application.

The long shots. We cannot deny that grid sampling has increased the amount of data from some fields, but this has seldom resulted in any opportunities for management. Fields that are highly variable, but where the lowest soil test is still high enough that no fertilizer is needed, do not offer any opportunities for fertilizer savings from more precise application.

At the other end of the scale, fields with very low fertility will respond more to added fertilizer than to more precise fertilizer application. Most in-between fields yield best with a uniform application of a low rate of starter fertilizer, and don't show enough extra response to variable fertilizer application to pay for the extra testing.

There are some parallels between the development of precision agriculture systems, and farm mechanization in the early 20th century. Sales of farm tractors were lower between 1900 and 1920 than they had been in the last years of the 19th century.

Historians claim that this lag in mechanization was not the result of economic forces, but because the early tractors had fallen so short of delivering the advantages that were promised. Widespread adoption was delayed until the technology matured to the point where it was reliable, economical and easy to use.

I expect to see a similar pattern in the adoption of precision technologies. BF

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