Managing Field Variability: How to Take Your Management to the Next Level

Written by Dr. Tracy Blackmer
February 14, 2016

Although many aspects in agriculture vary, the rate of change has increased to all facets of ag. In good economic times, I’ve found that growers are looking for new opportunities to take their management to a new level. But in financially challenging times, there’s a tendency to pull back on change. You may tweak what you’re already doing, but trying something completely new may seem like taking on undue risk.

In my experience, it’s during these financially challenging times when it makes the most sense to evaluate current management practices and ask if there’s an opportunity to adjust them.

And one of the biggest opportunities for gain is to adjust the management of your fields based on the variability within those fields.

For most growers, fields are variable. And if that’s the case—shouldn’t management vary? The is answer is intuitively yes: you should manage your fields spatially. But the more important question is how?

Below you’ll find five suggestions intended to help growers improve spatial management in trying times. All five suggestions involve refining practices you’ve most likely already adopted so that they include spatial variability.


 1. Understand the variability in your fields.

To manage variability, you need a way of identifying the variability within your fields. Measuring the differences in crop growth or yield is a good place to start because the difference in plant growth (which affects grain yield) is a good indicator of variability. Satellite imagery can be used to measure plant growth variability.


This satellite image shows some of the differences in crop growth based on field variability.

How to accelerate your plan with FarmLogs: With FarmLogs Crop Manager, we’ll send you multiple images of each of your fields throughout the growing season to help you track plant growth.


2. Manage yield response to management, not total yield.

Managing your field’s agronomy is key to unlocking the profit you can control. Although you’re paid on each bushel you produce, it’s the return on investment of each individual management practice that’s important here.

Some decisions you make on the farm require simple yes or no answers: you either use tillage or you don’t. You use specific seed treatments or you don’t. But if you’re managing your fields spatially, many decisions require an additional consideration: at what rate do you apply inputs?

For instance, you know you need to plant corn to harvest it. But at what rate should you apply it? If you assume a 80,000K unit of corn seed costs $300, that means you’re paying $3.75 per 1,000 seeds. As an evaluation do you know if the difference between the extra 3,000K of seed that costs $11.25 will give you more than that in yield increase? In other words, 30,000 vs. 33,000? Does it make sense that differences in the field that affect yield level will also change the best seeding population? The answer is field-specific. Fields without sufficient variability will not benefit. Fields with more variability will.


3. Know your management zones.

Not all variability should be managed the same. For example, in a given yield map, there are high- and low-yielding areas of the field. But for some decisions, knowing why the yield was low is important.

The eroded knoll vs. low lying/poor drainage areas may both have low yields but would benefit from differing seeding rates.

Some services will provide a general management zone as a combination of different data layers that the service provider assumes is useful for multiple or all types of management. This is a bad assumption in many cases.

For example, in a seeding prescription, a low yield from low soil moisture should be treated differently than low yield due to portions of a field that floods out every third year. Depending upon the input, you’d probably prefer to manage for the potential. For the portion of the field that floods out every third year, you wouldn’t want to use the three-year average of yield history but rather, the potential from the two years it did not flood out.

The big takeaway: management zones are often different for each specific management practice (i.e., the management zones for seeding rates are different than the management zones for N rates).


As your fields vary, so does your N uptake. Shouldn’t your fertilization application rate also vary?

How to accelerate your plan with FarmLogs: Variable Rate Nitrogen and Seeding Prescriptions make zone generation and management easy and intuitive. We generate the management zones for your fields and the prescriptions apply variable rates based on daily weather updates and the unique characteristics of each of your fields.


4. Dont wait for a yield monitor to give you feedback.

Yield monitors are a valuable tool but they don’t provide actionable insight for your current growing season. By the time a crop is planted you’ve already made a major investment. Instead of relying solely on your yield monitor maps to evaluate your field’s performance, we recommend monitoring your fields throughout the season to protect your investment.

In addition to your usual scouting efforts, try supplementing your efforts with aerial imagery taken throughout the season. Imagery collected throughout the season can be used to detect subtle differences in small parts of the field that a random scouting trip may not catch. Imagery can be used to look for differences between dates to identify new problems in the field being detected that can help guide ground truthing by scouting.

How to accelerate your plan with FarmLogs: FarmLogs Crop Manager includes in-season, field-specific Crop Health Imagery, and Crop Health Alerts, which alert you any time a potential yield threat is spotted in your fields. FarmLogs Crop Manager gives you a more efficient, more targeted way to treat zone-specific yield threats.


5. Set up your field to help you monitor what you want, when you want it.

Most growers are looking for at least one thing they can do in their operation to make it better. The question is how do you identify that one thing?

From an agronomic perspective, you need to focus on the question you want to answer and then set up a way to test the answer.

For example, a good question might be: “Am I using the right amount of N to raise my corn?”

To answer this, you can apply test strips with more or less N than you usually use and measure the yield differences.

By considering the fertilizer costs for each application rate in addition to the yield differences, you can get an answer. Know, however, that by using this method you’re most likely finding an answer that can’t be applied until next year. This isn’t an innately bad thing, because many people make the same mistake each year. But many growers are interested in knowing what they can do to help this season.

For questions relating to N management, there are in-season corrections that can help more immediately. Reference strips, for instance, could be placed in every field that has 50 lbs more N/acre than the rest of the field. These strips could be used like a canary in a coal mine–that is, when a difference in the reference strips is detected from the rest of the field, more N should be added.

It’s been documented that adding N as late as the silking stage can increase yield by 40 bu/a when it’s added in way that the plants can take it up.

Dribbling the fertilizer on top of the soil may not get down to the roots if there isn’t enough rain. But adding N with irrigate water (if needed) will help the plant take up the fertilizer.

How to accelerate your plan with FarmLogs: Another way to monitor the effects of your N management practices is with FarmLogs Nitrogen Monitoring, which is also included with FarmLogs Crop Manager. This tool shows you N availability and provides you with the status of N in your fields each day to indicate whether a new application is necessary.


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Dr. Tracy Blackmer


Dr. Tracy Blackmer Dr. Tracy Blackmer is an expert agronomist with over 20 years of experience incorporating precision agriculture technologies in agronomic management for growers. His work has included organizing a network of over 1,000 growers from 12 different states to conduct Nitrogen adaptive management using imagery, yield response, and other feedback assessments. Tracy also focuses on implementing large-scale, on-farm trials that are easy for growers to implement and result in improved agronomic recommendations. His work as the Vice President of Science at FarmLogs includes developing tools that improve local management for growers through better and simplified recommendations and monitoring.