Agronomy

When growers check their crops in season, they know what to expect, year after year, from certain spots in the fields where they are scouting. There’s the gumbo ground that holds water too long and reduces yield in wetter years. There’s the stubborn rocky knob with little to no topsoil, spots that have perfect drainage and deeper dirt and areas that consistently produce top yields. There is generally truth in the words when our grandparents and parents talk about the “money dirt.” 

Despite that historical knowledge and even with the amount of data our harvest equipment captures, sometimes it feels as if we stop short of potential. We end up looking at a pretty, color-coded map of successful and failing parts of our fields without truly using the information we have within our grasp. 

With good, calibrated yield data, however, we can create spatial trends by honing in on our best and worst yield zones in each field. Spatial trends allow us to identify and label spots that consistently grow above-average yields as well as spots with poor production. This data layer can be used to create variable-rate zones for fertilizer applications such as anhydrous ammonia (NH₃) or sidedress nitrogen and to generate precision planting prescriptions. In building the spatial data layer, we leave out years with disasters like hail, drought and mechanical mess-ups to ensure that we look at real-world trends.

With variable-rate corn planting prescriptions, we can label the lower-producing areas, and, keeping the average planting population to what we ordered in seed, reduce the rate in the poorer spots (tree lines, wet spots, wildlife feeding areas) and raise the rate in the spots that consistently contribute higher bushels. This pushes our potential in the best areas and saves inputs in areas that won’t ever produce. 

“Precision practices can help us farm with more consistency and efficiency, ensuring we spend input dollars correctly, down to the acre.”

Looking at early-season applications, we can take these yield trends and apply them to variable-rate anhydrous ammonia. If we plan for nitrogen use efficiency to be 1.1 pounds of N to 1 bushel of corn with a 200-bushel corn yield goal, the recommendation would be 220 pounds of nitrogen per acre. Being good stewards of our soils, and following 4R Stewardship principles, we would split apply this nitrogen through the season. This would consist of a base amount average of pre-plant nitrogen in either fall or spring, followed by an in-season sidedress application when corn begins to take off around V6-V7. This agronomic practice will ensure we are protecting our investment in wet years and potentially saving some applied N in the dry years. 

The variable-rate NH₃ prescription will be based on the year-end goal of 200-bushel average and the nitrogen use efficiency. Low productive spots from our spatial trends may only call for 60% to 70% of average, while better spots may call for 120% to 125%. Adding in factors such as a guaranteed 60-pound sidedress application and nitrogen credits from organic material will determine an equation for pre-plant NH₃. If we have 2.5% organic matter, and we count 20 pounds of N by unit of percentage from organic material, we will have 50 pounds of nitrogen credit (2.5 x 20). We plan to spread 60 pounds of N through sidedress application in season. Those two values, totaling 110 pounds, would then be subtracted from the average NH₃ prescription. The variable-rate prescription would then show an average of 110 pounds of N, while varying lower and higher across the spatial yield zone trends. 

To continue down the 4R Stewardship path, we would then add all these layers to our Nutri-Track N model. This includes grid soil sampling; planting date; crop maturity; tillage method; variable-rate seeding, yield and NH₃ application; and other aspects to make sure we are managing nitrogen correctly. 

With fluctuating markets, increasing input costs and volatility, weather patterns and other factors out of our control, there is more uncertainty in agriculture than ever before. Precision practices can help us farm with more consistency and efficiency, ensuring we spend input dollars correctly, down to the acre. Reach out to your local MFA or AGChoice solutions provider to learn more and begin the process.