Forage Focus: Pasture Fertility Strategy

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Most fertility experts would agree that nitrogen management is of great importance when attempting to economically increase forage yields of grass pastures or hay fields. There are many factors which may influence nitrogen use efficiency, most of which have been previously discussed in past articles. In this article we will look at a snapshot in time and how nitrogen application may influence economics on a mixed grass hay field.

Scenario:

It is July 1st and three weeks ago we completed the first cutting of our fescue. Our field soil test results are: pH =7.3; Phosphorus (P) =32ppm; and Potassium (K) =74ppm.

Our dilemma: Will it pay to add some nitrogen to this field and what quantity of nitrogen is most economical?

Important considerations impacting economics:
* we will utilize urea at $400/ton
* we value like forage at $100/ton Dry Matter (DM)

In this example we will utilize the results from a demonstration at the OSU Eastern Agriculture Research Station. The following amounts of nitrogen fertilizer were applied to 20 ft. by 20 ft. blocks of fescue. In each block is the amount of dry matter grown per acre (A) over and above the control (no nitrogen), harvest date of 7/30. In addition, represented in each square is the amount of forage dry matter grown per pound of nitrogen, over and above the control.



How did forage nutritional quality change with nitrogen fertilization? Below are the results of three analyzed plots taken 7/30, dry matter basis.



Key: Nitrogen=N; Crude Protein=CP; Neutral Detergent Fiber=NDF; Acid Detergent Fiber=ADF; Relative Feed Value=RFV

As expected, increased nitrogen application had a positive influence on forage crude protein (CP) content. Conversely, higher nitrogen application rates increased forage fiber content, resulting in a lower relative feed value.

What influence did nitrogen fertilization have on economics when compared to the control? Cost calculations are the cost of the fertilizer per acre, plus a $6 per acre spreading cost.



For these demonstration plots, fertilizing July 1st at the cost of nitrogen previously stated resulted in decreasing profits per acre (A). Keep in mind this is a snapshot in time and each season will have different economics specific to individual forage species.

In this next chart we look at the breakeven calculations for the various nitrogen application rates. The breakeven is what it actually cost us to produce this forage at the fertilizer cost mentioned previously.



In conclusion, forage species, seasonal growth concerns, fertilizer cost, forage value, and growing conditions are very important factors to consider prior to nitrogen applications. The economics of nitrogen fertilization changes seasonally and yearly. What will be your fertility strategy for this upcoming year?

Source: Clif Little, Extension Educator, Ohio State University Extension, Noble/Guernsey County



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