Nutrient Recommendations
By Jim Halbeisen
We want to discuss our contention that the 1.2 Rule, now being questioned by Blackmer but still followed by the agricultural establishment, is too high. (The 1.2 Rule says that you should apply 1.2 pounds of nitrogen for every bushel of corn you wish to grow.)
The October 2004 edition of Farm Journal had an article featuring Alfred Blackmer of Iowa State University who's research finds that the current recommended amounts of nitrogen are more than is necessary to achieve profitable corn yields. In future newsletter articles we will examine the nitrogen problem in more detail, however, for now, we want to discuss our contention that the 1.2 Rule, now being questioned by Blackmer but still followed by the agricultural establishment, is too high. (The 1.2 Rule says that you should apply 1.2 pounds of nitrogen for every bushel of corn you wish to grow.)
After World War II, fertilizer companies told farmers that soil fertility was an arithmetic game. For every pound of nutrient removed by the crop, you had to replace that pound-forpound with fertilizer. Then they started to inflate that rate so you would have a build up of soil nutrients which would be "like having money in the bank." Many farmers felt the buildup idea was too expensive, but they did go along with replacing the nutrients removed. Early in the history of Growers Chemical Corporation, Dr. V. A. Tiedjens used university research to show that the removal of nutrients by crops was quite variable. He backed his position by referencing the work of Dr. Kenneth C. Beeson which is found in USDA's Miscellaneous Publication No. 369, from March, 1941, "The Mineral Composition of Crops with Particular Reference to the Soil's in which They Were Grown.'' Dr. Beeson concluded, "There is an abundance of evidence that plants and their parts vary greatly and significantly in the principle elements when grown in different soils in different environments, or even in environments that differ only in small degrees. Out of the confusion of the contradictory results of the fertilization experiment, one can draw a few very definite conclusions. The necessity for a balanced source of nutrients for the plant is thus indicated, and the variance in results by investigators would tend to prove that this is a problem that can be solved only by the study of the characteristics of each soil type." Dr. Tiedjens published a concise summary of Beeson's work (shaded area) which is found in the Growers Nutritional Solutions Sales Manual. Looking at Dr. Tiedjens summary, it is quite obvious why nutrient concentrations can be so variable for different crops, why he suggested that farmers' land maybe did not need all the fertilizers recommended by the agricultural establishment's arithmetic method, and why the data proved to be a very effective
Growers sales tool for many years. The most glaring contradiction or problem in the arithmetic method, as we see it, is deciding how to calculate the pounds of nutrients removed by the crops. Which removal numbers can we use?
Prevailing authorities, with mounting skepticism, have always questioned the validity of Dr. Beeson's research in that it dated back to 1941.
Then in 2003, several authors from the eastern United States published an article in an early 2003 issue of the Agronomy Journal, entitled "Nutrient Removal by Corn Grain Harvest." Their research was directed towards Nutrient Management issues rather than for fertilizer recommendations, but they, in effect, although not intentionally, confirmed Dr. Beeson's 60 plus year old work.
These later researchers grew corn at established sites to reflect differing soils over a high total of site years. They analyzed the corn grain for the amounts of the nutrients; nitrogen (N), phosphorus (P), potassium (K), sulfur (S), calcium (Ca), magnesium (Mg), zinc (Zn), manganese (Mn), copper (Cu), boron (B) and iron (Fe). The object was to find out how many soil nutrients would be removed by the harvested corn grain over a range of growing conditions in the Mid-Atlantic region and to determine if nutrient concentrations in grain were related to the crop yield.
They stated that past extension fertilizer recommendations, which is what they used on the plots, took into account the needed replacement of nutrients lost to harvest. However, they wanted to see if nutrient removal by crops could also keep applied nutrients from reaching excessive levels in soils.
They found that the nutrient concentrations of P, K, Zn, and Fe in corn were only weakly related to yield.
Table I is a summary of the nutrient concentrations found in the research plots. The data shows they vary by a factor 1.5 for N, 2.5 for P, 2 for K and even higher for some of the micronutrients. The large variability of nutrient concentrations in corn grain surprised the researchers, and they could not explain why it happened.
Applied fertilizer could not account for the variability, because the same fertilizer treatments were used on all plots. Some thought the variability could be caused by hybrid differences, but that idea was eliminated by the analysis of a single hybrid across the testing area, Table II, which had variability very similar to that of the entire trial's.
The researchers concluded that grain nutrient concentrations can be highly variable even for a given corn hybrid grown in different environments. This research also showed that there was no relationship between nutrient concentrations and yeild. The researchers concluded, "Even though average volumes of corn grain nutrient removal in this study are similar to existing reference values, the variability seen in this study raises questions about the usefulness of average values for estimating crop nutrient removal across a range of conditions. Livestock producers should also consider the implications of nutrient variability of grain in ration balancing for the mineral nutrition of their animals."
Trying to make fertilization rate recommendations by merely assuming general nutrient extractions, such as multiplying 1.2 times anticipated corn yield to predict needed pounds of applied nitrogen (1.2 Rule), is a very inexact way of fertilizing the crop, as is trying to use the nutrient concentrations to predict profitable yeilds.
It seems this modern day 2003 research goes a long way towards replicating Dr. Kenneth C. Beeson's sound fundamental research published in 1941. We all need to know that the essentials of science are constant and modern day bells and whistles do not change the basics. Unlike his peers of a half century ago and their counterparts of today, Dr. Tiedjens early on recognized the inconsistent availability of soil nutrients to growing crops. This explains why he aimed his efforts towards directly feeding plant seeds and foliages with nontoxic plant foods (GNS) while addressing soil fertility issues with the Growers Program.
