Every year we evaluate our management practices to see how we can improve our efficiency. Selecting the right hybrids and varieties are key to our success, but fine-tuning our fertilizer program has also paid big dividends.
There are three main areas that have been key to our fertilizer program’s success: soil testing, proper fertilizer selection and using technology to appropriately apply fertilizer in a time, space and form that allows the crop to access these nutrients most efficiently.
Soil Test Frequently
Our fields are sampled on a 2-acre basis every 4 years so we can get a handle on the field’s variability in pH, phosphorus (P), potassium (K), organic matter and cation exchange capacity, as well as soil characteristics, such as soil type, water holding capacity, soil texture and more. This intense sampling helps us determine how we should manage each individual field.
The soil test data is then put into our precision ag software so we can develop prescription maps for lime and dry fertilizer applications. We variable-rate potash in the soybean years and P on in the corn years to meet our fertility goals.
Dry vs. Liquid
When developing a fertilizer program for your farm, it’s important to think about how to reduce the risk of losing fertilizer and the most economical way to build your soils up to a productive level. Product selection and timing of these applications can have a large impact on how successful you are at achieving these goals.
It’s important to think about the size of the plant’s root system when you are applying the fertilizer, and how you can place the fertilizer so the plants can take up the nutrients efficiently. We try to feed the corn plants in several ways so the fertilizer is easily accessible to the plant throughout the growing season.
Because they are generally more economical than liquid fertilizers, we use dry fertilizers as much as possible to provide our P and K needs, and some of our nitrogen (N) and sulfur requirements. However, we do use liquid fertilizers on the planter to provide more precise placement of nutrients near the small seedlings so the plants can easily access the nutrients.
Dry fertilizer starters would also work well if we had a smaller planter, but with a 24-row it’s much easier to use liquids to distribute them and to hold down the weight of the planter. With the larger planter, we only carry enough fertilizer to get the seedling off to a good start and the majority of our P and K fertilizer is applied through a broadcast system.
We also provide the nutrients in a way that reduces the possibility for them to be lost. Selecting N products that are more stable so they have to go through more conversions before they can be leached or denitrified helps to improve N use efficiency.
There is a lot of popular press about the use of 28% and 32% liquid N sources with some applied pre-plant and the balance as a sidedress. We have tried these solutions in our field trials over several years and never really can get the same yields and N use efficiency that we get with anhydrous ammonia, so we continue to use a combination of dry and liquid fertilizers. The biggest share of N is supplied through pre-plant anhydrous stabilized with N-Serve.
From Start to Finish
We apply 5-6 gallons of 10-34-0 under the seed to give it adequate N to get started and nearly half of the total P the crop will need. We dribble in 5 gallons of 28% N and 2½ gallons of ammonium thiosulfate through a 2-by-0-inch band off the back of the planter. This allows the small plant to easily access these nutrients as it’s developing its root mass.
The liquid fertilizers are more expensive than the dry sources, but are easier to apply with our large planter, and the fertilizer application attachments for the planter are more economical. The cost of these nutrients in a liquid vs. dry form is about $5.00 more per acre. We feel we easily get that back from the starter fertilizer, which normally provides an increase of 7-8 corn bushels per acre on our farm.
The total K and the rest of P needed for the corn is variable-rate spread before planting as potash and diammonium phosphate (DAP). Ammonium sulfate is added to this blend to provide additional sulfur and another source of N for the plant as its roots are developing.
The biggest share of our N is applied as anhydrous ammonia in 40-inch bands with N-serve in between every other row of our 20-inch planting system. The other fertilizer products provide our small plants with easily accessible forms of N that are close to their small root systems.
As the plant then reaches V4-V5, it has a large enough root system to access the deeply placed anhydrous, which has been stabilized but now converted to a form the crop can use.
We concentrate the N in 40-inch bands and use the stabilizer to delay the anhydrous from volatilizing, so the crop can efficiently use the N and it isn’t lost. Soil bacteria help to convert the anhydrous to nitrate and nitrite forms of N, which are then plant-available.
Having the ammonia more concentrated in fewer bands in the field slows the ability of these bacteria to convert the N, hence the N band remains stable for a longer period of time, providing N longer into the growing season.
We feel this system provides us more usable N to the plant than sidedressing liquid N would because the anhydrous is more stable and the concentrated band reduces conversion rates. Also, with our 20-inch rows it would be hard to sidedress without root pruning.
Another way we have improved this system is by using RTK guidance and a variable-rate N controller to apply the N. This allows us to precisely apply N with guidance lines so our planting passes are perfectly in between the N bands, which ensures there is no loss of stand over the N seams because we are planting in between the bands, and it allows each row equal access to the N.
This also allows us to apply the anhydrous within a day of planting without the fear of losing a stand. In the past, we would have to put the N on 7-10 days before planting to ensure we wouldn’t have germination issues if we were over a N band. Thus we are putting the N on much later, which again helps to reduce the risk of N loss. The planter also works much better when the openers are running in firm soil away from the anhydrous knife mark.
Our system is designed to match the nutrient placement with the crop’s uptake of the nutrients and to provide nutrients that are stable and used efficiently throughout the growing season. The fertilizer products we have selected are also generally the most economical form available.