Summer 2008

Changing Nutrient Values Mean 'New' Focus on Manure

PRINT VERSION (pdf) Download the Summer 2008 issue of Iowa Manure Matters - Odor and Nutrient Management Newsletter in pdf format.

By John Lawrence and Joe Lally, Iowa Beef Center, Iowa State University

Commercial fertilizer rates continue to increase. Prices for N-P-K booked for the 2009 crop have increased 90, 55, and 160 percent, respectively over the spring 2007 prices used in this exercise. The message is the same. Manure has value and implementing a nutrient management plan is essential to capturing its fullest potential.

Nutrient management planning pays a lot of attention to balancing available nutrients from manure to the nutrient needs of crop production. One perspective looks at whole farm balance which accounts for nutrients entering the livestock farm in the form of purchased feed, fertilizer, animals or as nitrogen (N) fixed by legumes, and the nutrients leaving the farm in the form of animals or crops. Any imbalance between inputs and outputs could be added to soil reserves or lost to the environment. Nutrient planners evaluate this balance at the field level or even within a field. They develop a plan that is often defined by regulations or guidelines set by state or federal agencies.

When it comes to nutrient management most farmers have three objectives. First as stewards of the land and water, they want to do the right thing. Second, if they have a permit or an EQIP contract they are legally bound to implement their plan. Third, they are in business to make a profit. Between 2002 and 2007 commercial fertilizer prices have doubled aligning all three objectives are more closely.

Table 1 illustrates how the value of manure has increased as the April price of commercial fertilizer has risen. The price of N rose from $0.19 / unit in 2002 to $0.42 / unit in 2007 or a 121% increase. Similarly, the P205 and K20 per unit costs have increased by 87% and 77%, respectively. As a result, the value of manure in a corn-soybean rotation has doubled in five years.

Table 1. Impact of Changing Commercial Fertilizer Prices on the Value of Manure

The assumptions used in this table include:

  • 1,000 Animal Unit Capacity Farm.
  • 2002 Fertilizer Prices per unit  N: $0.19; P2O5: $0.24; K2O: $0.14
  • 2007 Fertilizer Prices per unit: N: $0.42; P2O5: $0.45; K2O: $0.23
  • Corn-Soybean (C-B) rotation, manure applied ahead of corn; 200 bu. Corn; 60 bu. Soybean.
  • The land receiving the manure can utilize the nutrients and achieve the yield goal
  • Multi-year application of P205 and K20 and nutrient applications will stay put until the growing crop demands the nutrients.
  • Additional N is added to corn in year three of four year rotations.

The opportunity to utilize manure nutrients will depend on the management activities governing the capture of the nutrient load. Nitrogen, the leakiest element of all three will escape to the environment if given no consideration for its value or volatility. Land treatments, rotations, tillage practices, timing of application, and environmental influences all contribute to successful manure handling and application of this source of natural and essential crop nutrients.

The value of manure nutrients is an opportunity to capture value according to specific needs of the crops. Farmers can capture greater value, greater profit, by putting manure nutrients where they are needed. That is where a nutrient management plan is essential. Now that manure has more potential value, producers have greater incentive to manage nutrients more closely by following a nutrient plan that incorporates agronomics and stewardship.


This article originally appeared in the November 2007 Heartland Animal Manure Management Newsletter.


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