Fertility strategies to consider this fall

In a high-cost year, re-examining your fertility approach can save you money.

How should you be approaching fertility planning for 2025 crop when fertilizer costs are high and crop prices are lower at this time of year? This is a question we’re seeing from across the country. Not only does re-examining your fertilizer approach save you money when implemented correctly, but it can also reduce environmental impacts. Soil health practices include 4R management which means focusing on the right source, the right rate, the right time, and the right placement. Using the 4Rs as your starting point can help you think through all the options available to you when planning your fertility program.

Two considerations you should make before determining your fertility rate include:

1. Soil sampling helps you understand your nutrient needs.

Soil sampling is the easiest, cheapest way to know what nutrient deficiencies and holding capacity your soil has. Grid and zone sampling can allow you to become even more exact in determining your nutrient rates, especially when yield data is overlayed onto your sampling data. While grid and zone sampling are more expensive than traditional composite sampling, they give a much better look at the variables throughout the entire field, allowing you to apply the right rate on each acre.

2. Soil pH determines nutrient availability.

Soil pH is a driving factor for nutrient availability in the soil. The chart below shows nutrient availability in the soil. The optimum pH for row crop nutrient availability is between 6.2 and 7. Soil pH outside of this range can lead to reduced nutrient availability as well as herbicide carryover. For acidic soil below 6.2, consider adding ag lime to raise your soil pH to optimum levels and increase nutrient availability.

^{pH chart source: No-TillFarmer.com}

Formulate your fertility plan around 4R nutrient management

• Right source 

Determining the nutrient cost for available fertilizers in your area may allow you to save money on inputs, but it is important to make sure quality is not sacrificed. For all nitrogen fertilizers, consider adding a stabilizer to reduce volatilization and leaching. For phosphorus, calculate whether monoammonium phosphate (MAP) or diammonium phosphate (DAP) will provide the most bang for your buck. With more options available it is important to work with your local resources to determine what product is right for your needs.

During times of high fertilizer prices, many farmers look to alternatives such as manure and litter. While these are great sources of many nutrients and, at times, can be cheaper than commercial fertilizer, it is important to remember there will be variability in the product. Periodic sampling of each load/barn is important to make sure the desired rate is being applied.

• Right rate 

When calculating nutrient requirements for the upcoming season, nutrient removal rates can be a great tool to have handy when looking at soil tests and developing a cost-effective fertility plan. Referring to crop removal rates gives you an estimate of the minimum amount of nutrients to apply for your desired yield goal. Keep in mind, this does not take into consideration any nutrient loss from weathering.

Technology also allows variable rate fertilizer to be applied based on the yield data from harvest. Implementing harvest data allows you to replenish the nutrients removed from each acre of the field. This can be a great cost saver, especially in areas experiencing drought.

With continued drought conditions, it is vital to pay close attention to your potassium numbers and make sure they are in line with your CEC. Potassium plays a vital role in the water balance and movement within the plant.

^{Chart source: GoldenHarvestSeeds.com}

• Right time

While split-applying nutrients may cost more in application, when you space out the application of nutrients such as nitrogen, this can help ensure that the rate applied is available for the plant when needed. As pictured in the chart below, N usage in corn increases drastically once the plant reaches V-11, yet across many parts of the country, most of the nitrogen for a corn crop is applied before planting. Split-applying N allows you to better utilize your nitrogen application and make management decisions based on the crop potential and growing conditions. As you consider split-application of N, remember to factor in the equipment available in your area. Applying N late in the season to a corn crop will require either a high-clearance spreader/sprayer or having it flown on. Planning ahead is necessary to make sure the required equipment is available to you when needed.

You’ll also need to consider your P and K applications. If you apply in the fall, will your application be protected if/ when the heavier spring rains come? You spend money on these products, make sure they’re protected. We see more often that a living cover crop will hold the soil and will do the same for your fertility.

^{Chart source: Pioneer.com}

• Right place

Nutrient placement is a combination of both the source and the application method. Some fertilizers react with the air and will volatilize unless placed underground. Similarly, fertilizer mobility will influence where it is placed. Immobile nutrients need to be placed close to the plant roots while mobile nutrients shouldn't be placed too deep. Placing mobile nutrients too deep could cause those nutrients to travel outside of the root zone before they are used. Fertilizing at the right time will positively influence your placement as well.

Your equipment will limit your ability to choose your placement. If you are interested in trying different placement methods, we recommend renting or using the co-op.

 

Don't forget that weather will always play a role, so control what you can. Using 4R management can give you a better insight into the positive and negative impact of what products, application timing, and method have on your operation. This insight can be enhanced with the use of soil sampling, which will take the guesswork out of what nutrients you already have available.. Knowing which nutrients need extra support and which ones are abundant in your soil will definitely pay off when it comes to your fertility plan.