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What we have learned from probes this year

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What we have learned from probes this year

Lately I’ve seen many services, products, and solutions on the market for producers that deal with water management. It’s no secret that by focusing on water, there is huge potential to increase yield, increase profits, and become more efficient with our inputs. Over the past season to date, I have noticed a few agronomic events that have been critical to our crop development in the Midwest that we couldn’t learn unless we had soil moisture probes installed in the fields. By focusing on aspects of the crop that are easy and scalable, the agronomic details for success can often be lost. For this reason, I wanted to talk about the factors we learned from probes themselves this season to date.

Early in the season, one of the biggest agronomic pieces of information we saw with soil moisture probes across the Midwest was water movement from the lower depths of the profile to the top. Water from the lower profile was moving up through the profile through adhesion of the water to the soil particles, and cohesion of the water molecules together from higher concentrations of water to the lower concentrations drying at the top from weather evaporation and crop transpiration. The early season cool weather and precipitation (rain and snow!) let us begin with a full profile in many parts of the Midwest, and this movement of water helped us hold off on irrigations until late June and early July. This movement of water could only have been seen by utilizing a soil moisture probe, and without this knowledge applying early could have led to many detrimental effects. 

Migration of water*Migration of water early in the season from the lower depths of the profile to the top, where weather and crop use depleted water resources.

To stay on the water use trend, currently in early August many soil moisture probes across the Midwest have seen lower crop water use rates and even flatlining on graphs which is opposite of what we typically expect in the reproductive stages of crops now. In the past, we would have thought due to ears of corn filling and soybean pods growing and filling we would have been applying due to the hot temperatures outside. The thing about hot temperatures, is that they only tell us a part of the story and by only applying because it is hot out can hurt crop success. Many probes through the reproductive stages of our crops this season are experiencing lower crop water use due to extremely high humidity across the Midwest. This humidity has helped reduce crop water use and demand, and with high humidity and sufficient moisture in the profile even temperatures to 98oF have no effect on yield.

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*Humid and foggy morning over soybeans in early August.

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*Reduced crop use due to increased humidity in Central NE. Corn in this field was just entering the milk stage.

By using soil moisture probes, we have been able to see exactly what the crop is using and how much water is available to that crop based on the stage and soil in each individual field. Probes allow us to be proactive instead of reactive, doing everything we can to give the crop water at the right time, in the right amount, and in the right spot instead of reacting after stress has occurred.  Viewing an image with visible stress means that stress has already occurred, and utilizing a probe let’s us know exactly where we are at with water available to each crop. Just basing an irrigation event on temperature on date would have caused over application, and misapplication throughout the entire season.  If we had just been applying based on estimated reference Evapotranspiration (ET), we would have been over applying irrigation on fields where ET forecasted to be .25-.3” per day and the crop use ranged from .12”-.24” in many fields. By knowing exactly what is happening in the profile with the probes, we were able to put on the right amount of water at the right time. On the other side of application, we also were able to see exactly how much water got into the profile and how deep the water percolated. Without a soil moisture probe, this would be impossible as well. Just because we got an inch of rainfall does not mean that that inch all infiltrated into the profile and gave us a +1” in our soil moisture bank account. If that inch came in an hour or in 10 minutes, the depth could greatly vary, and knowing where the water is and where the active roots are pulling is critical for crop success.

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*This is the corn ear from this field with reduced water use from the graph above and only 5.5” applied to date. 42×16 average with a 33k even stand with 235 bu/ac yield goal. This field has 28” of ACTIVE roots in the profile which means the CropMetrics Certified Dealer is managing water based on a 28” profile of soil water.

I mentioned above about knowing how much water is available to the crop in each individual field. This is impossible without understanding the Volumetric Water Content of the soil looking at multiple depths, combined with the agronomic knowledge of the soil structure and texture in our profile. With soil moisture probes, we have been able to change our recommendations based upon the active uptake of roots and the depth of these roots in the profile. Looking at 4’ of water in a profile when the crop only has 2’ of roots doesn’t make much sense, and Certified CropMetrics Dealers are able to recommend irrigation events based upon the crops current stage and current root depth and use – all seen by the CropMetrics system. Without a trained agronomic professional working to install the probe and note changes in the soil profile at install, many of these management aspects can be lost. As we install a probe we take note of soil changes vertically in the profile and adjust irrigation recommendations based upon these changes. A sand in the first foot of a soil, with a loam in the second foot can completely change the management of a field compared to a field with sand at the first and second foot. Without someone in the field checking and working on this, water management is a guessing game for root depth and root environment. This change in root depth and water available based on soil composition is also a great way to take advantage of soil based agronomic VRI. By applying water where it is needed by the crop across a field, success continues by being proactive in management. By viewing an image with differences in plant health across a field, chances are the stress has already begun. By utilizing a probe being proactive on water amounts when they are needed, VRI can place the water where it is needed across the field and in the right amount! This all occurs before visible stress happens on the crop itself.

A probe itself; however, is not a stand alone solution. Probes are able to record historical data with many points, while the telemetry unit transmits that data where a Certified CropMetrics Dealer is able to translate that data into actionable events in a field. Not only using the historical data from the probe, where the plant and soil tell us information, but also utilizing field level weather information and forecasts tied to crop modeling and forecasting to help us identify how to plan ahead in conjunction with the probe data. A probe alone will only give historical data, and dealing with living and growing crops in an uncontrolled environment we have to be proactive in managing and forecasting the future of that crop.

With many ways to look at irrigating a crop next season, remember that not every answer can be solved by just weather data or images alone. The life of our plants is found in the roots and the soil, and soil moisture probes give us the opportunity to watch that life progress from start to finish.

 

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