An economist was overheard saying that there were 5 ways to increase profits in any production system: cut costs, cut costs, cut costs, cut costs, and increase yields. This was somewhat a joke but has a solid underlying basis. Let’s delve a little deeper into this strategy with some specific examples and practices to follow. 

Yields are influenced by soil and weather conditions, soil pH and nutrient fertility status, and by pests (insects, diseases and weeds). The number one yield limiting factor for most Kentucky row crop producers is water, either too much or not enough. Water management is more of a long-term production decision regarding installation of irrigation and/or drainage systems that we will leave to the engineers. 

Controlling insect, disease and weed pests is another management practice that can have a huge impact on final yield and profitability for any given year. For now, we will also assume producers are using good pest management strategies and following IPM practices/thresholds to make spray decisions. 

As soil scientists, we’d like to discuss soil pH and nutrient availability. Both of these concerns can be addressed by proper soil sampling and testing. A standard soil probe is capable of making (or saving) a producer many dollars per acre when used correctly. A properly collected soil sample will provide a producer, or their consultant, with the current fertility status of the sampled fields. Knowing this for a field is paramount to knowing the right amount of lime, phosphorus, or potassium to add to that field, if any is actually needed. Remember that there are two ways to lose money in your soil fertility program; adding something you don’t need (wasted input costs) or not adding something that you do need (reduced yield due to poor soil fertility). Soil sampling and testing can help avoid both of these perils as you manage your soil fertility program.

A good soil sampling and testing routine should be the basis of any soil fertility program. The first step is to properly identify the area of interest, typically no more than 10 to 20 acres in size (depending on field uniformity), sampling to 4 inches in no-till fields and 6 inches in tilled fields, and making sure to avoid anomalies within that area that might greatly affect test results. Submit the samples to a lab with a good reputation that uses soil test procedures appropriate for soils of the of the area/region. Soil extractants are developed to provide an estimate/index of nutrient availability for crop use in the coming growing season. These extractants can vary with region as native soil conditions can vary considerably (e.g. acid, alkaline, saline, etc.). In Kentucky, we are best served by using the Mehlich 3 extractant that was developed for acid to neutral soils in the southeastern U.S.. There may be several soil test labs in the area that use the same extractant but be aware that they might report results differently. The two most common reporting methods are lb nutrient/acre or ppm nutrient in the sample. The conversion between the two is simple: multiply ppm by 2 to convert to lb per acre, or divide lb per acre by 2 to get ppm. Make sure you understand the unit your chosen lab is using.

Spring soil samples will differ slightly from fall soil samples. For continuity of interpretation, be sure to collect soil samples at the same time of the year. This allows a producer to compare the historical soil samples with the current ones and make changes as necessary. Comparing the soil samples over time, along with good fertilizer application records, will allow the producer to make adjustments for individual fields as needed. 

Once good soil samples are collected, and then analyzed in a good laboratory, the next thing is to evaluate the results for individual fields. Follow soil test recommendations for the individual field. Don’t average soil test values across multiple fields – apply what is needed to the field that needs it. Generally, the best bang for the soil fertility buck is going to be soil pH management. Row crops perform best at a pH around 6.5. Maintaining a pH in this range optimizes availability of phosphorus and micronutrients, promotes good root growth and health and can positively influence the activity of certain herbicides. 

How do you decide what nutrients or soil amendments should be added if the budget is limited? Liebig’s Law of the Minimum is a good rule to remember when deciding which nutrient(s) to add. It states that crop yield is proportional to the amount of the most limiting essential nutrient. In other words, the addition of a non-limiting nutrient will not maximize yield if the limiting nutrient is not addressed. Adding potassium to a phosphorus deficient soil will not remedy phosphorus deficiency or vice versa. Adding phosphorus to a soil with a pH of 5.3 is not going to be as effective for improving yield as liming the field and increasing the soil pH.

In very tight times with limited fertilizer budgets, rates might need to be cut in order to get several needed nutrients on the field. At what point is yield being lost due to a reduction in fertilizer additions? In these instances it would still pay to address soil pH. Work from The University of Tennessee showed that a half rate of limestone was almost as effective in neutralizing soil acidity as the full recommended rate - the benefit just didn’t last as long. You can cut lime some, but acidity will eventually have to be addressed. Soil test values in the high range don’t call for a fertilizer addition. Crops growing on soils testing in the ‘medium’ range are less likely to respond to fertilizer additions, especially when at the higher end of the medium range. The soils testing in the ‘low’ range for available nutrients are most likely to limit crop growth and are most likely to profitably respond to fertilizer addition. These are the fields to address first, followed by fields testing in the low end of the medium range.

One thing to avoid is using a “miracle product” that claims to replace conventional fertilizers at a fraction of the cost and nutrient rate. There are plenty of products available that have remarkable claims about reducing overall soil fertility needs. Be skeptical of products with claims like, two quarts per acre replaces X pounds of dry fertilizer. A pound of fertilizer is a pound of fertilizer regardless of the form. For example, a gallon of ammonium polyphosphate (APP, 10-34-0) weighs about 11.7 lb and contains about 4 lb P2O5. To obtain 50 lb P2O5/acre using APP will require 146 lb or 12.5 gallons APP/acre. To get the same 50 lb P2O5/acre with DAP (18-46-0) requires 109 lb DAP/acre. This 50 lb P2O5/acre will not be replaced by a product at a use rate of 1-2 quarts per acre, regardless of their claims. Don’t spend $5 to $20/acre on these types of products in hopes of replacing a proven lime or fertilizer product – the money is better spent on proven products.

Maybe the opening paragraph should read “make well informed decisions and don’t waste money where it isn’t needed” rather than cut costs, cut costs, but that wasn’t as catchy. We didn’t really tell you anything special or new, we just promoted that you use good basic agronomic principles. Maintaining good yields and watching the budget comes down to following basic crop production principles. If you can manage costs wisely while maintaining good yield potential in your fields, then you are in a better position for the seasonal weather to give you a nice profit. Take good soil samples and submit them to a reputable lab using appropriate soil test procedures. Evaluate all fertilizer and lime recommendations carefully, with an eye towards controlling costs. Soil sample analysis cost ranges from $0 (free) to about $10 per sample. What other important management practices can be completed at such a low cost? Address soil pH when it falls below 6.0 to 6.2. Match fertility applications to soil sample recommendations. Don’t average fertilizer rates over several fields – apply what is needed where needed. When budgets are tight, address low testing nutrients first, then those at the low end of the medium test range. The lower the soil test value the greater the chance for a profitable crop response. Don’t spend money on miracle products that merely claim to replace proven fertilizer products – go with what works.

Optional Citation: Ritchey E., Grove J., 2025. Follow the Basics to Maintain Yields and Manage Costs. Kentucky Field Crops News, Vol 1, Issue 2. University of Kentucky, February 14, 2025