There Is No Substitute for Adequate Crop Nutrition
The recent volatility in fertilizer prices, fluctuating commodity prices, and the global financial
situation have created a real sense of unease for many farmers. These conditions can create a “wait and
see” mentality that leads to counter-productive indecision for the upcoming season.
Fertilizer costs can be one of the most significant expenditures for producing many crops. However,
fertilizer costs are one of the expenses that can be thoughtfully managed. When applied properly, fertilizer still provides an excellent return on the investment and makes a vital contribution to overall farm profitability. The changing fertilizer and commodity prices may influence the optimal rate of application
– a decision that is individual for each crop, field, and farmer.
One commonly used tool for guiding fertilizer application decisions is
the ratio of the price of the input compared to the market price of the
additional crop being produced. While this tool is not a perfect measure, it
remains a good estimate of potential profitability. As crop and fertilizer prices fluctuate, this ratio rarely calls for large changes in application rate. Instead, it demonstrates the importance of getting the most value from all of the inputs used for crop
production. Efficiency is the term that reminds us that maximum return must be
squeezed from every farming input.
cost per bushel means that the farm is operating efficiently
… a characteristic of profitable farms.
Begin by using soil testing to identify the areas of
the farm that are in the greatest need of fertilizer
applications. Adding nutrients to low-testing soils is one
of the best investments because the probability of a large
yield response is high and fertilizing these zones quickly
provides additional income. Using good information allows nutrient management decisions to be based on sound
agronomic principles to maintain profitability. In these
economic conditions, it is not acceptable to make crucial
fertilizer decisions without this essential test.
225
Corn Grain Yield, bu/A
The yield boost from
proper crop nutrition
Photos by Corey Davis
helps spread fixed and
variable costs over more harvested bushels, thereby lowering the production cost per bushel. Lower
200
Soil K: 139 ppm
Yield = 211 bu/A
N Rate = 180 lb/A
175
150
Soil K: 80 ppm
Yield = 167 bu/A
N Rate = 280 lb/A
125
100
0
80
160
240
N Fertilizer Rate, lb/A
Figure 1. High yields of corn are obtained with less N
when other nutrients, such as K, are present in adequate
concentrations (Ohio). Balanced nutrition is key to improving yields and minimizing N fertilizer loss.
Source: Murrell and Munson. 1999. Better Crops. 83(3):28-31.
Areas of the field that are in the “medium” range likely require annual fertilization, or at least
sufficient additions to account for the nutrient needs of the crops being grown that year. Building
soil fertility levels to the higher side of “medium” or into the “high” range reduces the risk that some parts of the
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field are underperforming due to a lack of nutrients. Additionally, farmers who have previously invested in building
soil fertility to the “high” range may be able to skip an annual fertilizer application where appropriate.
It is too common to pay attention to single nutrients, perhaps due to specific fertilizer prices or a
field history. But plant nutrients interact to provide benefits beyond those achieved from a single nutrient. For ex-
ample, it is well known that an adequate supply of K is required in order for N fertilizer to be effectively utilized. In
one example where K was lacking, maximum corn yields were depressed by 44 bu/A – even when an additional 100
lb N/A was applied (Figure 1). The presence of adequate K
allowed the corn to achieve maximum profitability at much
Benefits of Adequate P:
lower N application rates. As frequently observed, a smaller
increased nodulation and N fixation
percentage of the applied N fertilizer was left in the soil after
harvest when soil K was adequate. Balanced application of
better water use efficiency
all the essential nutrients is required to ensure that crops
improved disease resistance
reach their full yield and profit potential.
higher crop quality
When fertilization is skipped, soil nutrient concentrations gradually decline. The rate at which various
nutrient concentrations decline differs for each soil and
also depends on the quantity of nutrients removed in the
harvested crop. When the nutrient concentration in a field
is in the “low” or “medium” category of soil fertility, there
is a likelihood of suffering significant yield loss by omitting
fertilizer. This practice would certainly not be recommended
in a field that is in this low nutrient state. In addition to
yield loss, any short-term savings will ultimately need to be
repaid in additional fertilizer to compensate for the nutrients
extracted in the harvested crop.
Fertilizer remains an essential investment each
year. There is no substitute for adequate crop nutrition.
earlier maturity
increased root growth
Benefits of Adequate K:
increased nodulation and development
increased ability to withstand drought stress
improved disease resistance
higher crop quality
increased grain development
increased kernel plumpness
reduced lodging
improved winterhardiness
better N use efficiency
Farmers who carefully monitor their soil nutrient status
will benefit through increased yields and are more likely to
get a favorable return on the overall farming investment. But additional attention needs to be given to getting the
most benefit from these inputs. Use every tool available to choose only the fertilizer products that are needed, keep
accurate field records to predict the right fertilizer application rate, apply nutrients at the right time to meet crop
requirements, and place the valuable fertilizer in the right place to get the maximum benefit.
Abbreviations and notes: N = nitrogen; P = phosphorus; K = potassium.
For related topics, go to www.ipni.net/fertilizer2009
Decision aids to help farmers and advisers make more informed decisions are
available in the Toolbox section of IPNI’s website: www.ipni.net/toolbox.
From the Scientific Staff of
3500 Parkway Lane, Suite 550
Norcross, Georgia 30092-2806 USA
Phone 770-447-0335 Fax 770-448-0439
www.ipni.net
Ref. # 09052