Soil Management

A Quick Guide to Basic Nutrient Management Concepts on eKonomics

Cristie Preston, Ph.D.

Cristie Preston

Cristie Preston, Ph.D.


Senior Agronomist

Agriculture has always been an integral part of Dr. Cristie Preston’s life. She grew up in southwest Virginia and had interest in crop and animal agriculture since an early age. Once she began college, she initially chose to study animal science but switched to soil science. Dr. Preston attributes her decision partly to an influential professor who told her, “You can’t understand animals until you understand what they eat.” She received a Bachelor of Science degree in animal science and a Master of Science degree in crop and soil environmental science from Virginia Tech. Dr. Preston holds a Ph.D. in agronomy, focusing on soil fertility from Kansas State University. While completing her advanced degrees, Dr. Preston conducted more than six years of field and lab research. Dr. Preston has experience in laboratory research measuring volatility loss from urea-based fertilizers. Her field research has focused on phosphorus availability and the interactions with tillage and placement. She also has extensive experience in working with large data sets and analysis. Her main priority is helping growers to identify yield-limiting factors and fix those issues as cost efficiently as possible.

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When it comes to nutrient management, every agronomist and farmer should be familiar with several basic concepts. From how to take the ideal soil sample to determining rates, farmers can maximize fertilizer efficiency and their profitability with these four concepts highlighted on eKonomics.

The first step is to take the best soil sample. By determining the amount of plant available nutrients in the soil, a farmer can better plan for supplemental fertilization needed to maximize yield4 Steps to achieving the ideal soil sample

A farmer’s maximum yield will be limited by the most limiting factor – Liebig’s Law of the Minimum – which means continually adding more nitrogen will not increase your yield if potassium has become the primary limiting factor. We have all seen the “barrel” of crop inputs and how each factor affects the water (or yield) within the barrel. However, at eKonomics, we believe a dam gives a better representation of how yield may continue to “leak” from behind the dam if all nutrient needs are not met. Why investing in only nitrogen this spring, may cost you dollars this Fall

Soil sampling is an imperfect science. It is common knowledge that nutrients, like phosphorus, have high spatial variability at the field level. When soil test levels fall below critical levels – the point at which the probability of a fertilizer response decreases – most farmers recognize they need to apply fertilizer. However, since soil sampling is an average of the area sampled, there are areas of low and high soil test levels within that area. Fertilizer management practices, such as The Maintenance Approach, assure soil test levels are built up so the chances of those nutrients being limited are reduced. Fertilization: comparing the maintenance approach vs. the sufficiency approach

By estimating the nutrients removed with grain or stover/straw harvest, farmers can at least apply the nutrients removed the previous year. The Nutrient Removal Calculator can be used to determine the amount of nutrients a crop will take up and remove at a given yield level. Nutrient Removal Calculator – Learning How to Use this Tool

There is no one-size-fits-all approach to crop production; however, by utilizing these basic agronomic concepts found on eKonomics, a farmer can better their chances of increased fertilizer efficiency and their bottom line of increased profitability.