Ohio Livestock Manure Management Guide

Bulletin 604-06

Chapter 2—Whole Farm Nutrient Budget/Planning

Introduction

Source: Adapted from the Livestock and Poultry Environmental Stewardship curriculum, MidWest Plan Service (MWPS). Used by permission.

Over application of manure is a major concern for water quality and soil health. Nitrogen and phosphorus are two nutrients that can hurt the quality of our groundwater and surface water. Nitrogen leaching out of the root zone may enter a tile and be transported to surface water, or it may leach to the groundwater. Phosphorous leachate or runoff entering the surface water contributes to excessive algae growth which causes low oxygen levels in surface water. This, in turn, impairs aquatic life. Proper management of manure is critical to protecting water quality and to sustaining the livestock and poultry industry.

The key to preventing manure nutrient overload is to balance manure nutrients with crop needs. However, as livestock and poultry operations get larger, the manure nutrients generated often exceed the nutrient needs of the crops on the farm. When more manure nutrients are applied to the crops than the crops can use, nutrient levels built up in soil, leading to a higher risk of nutrient runoff or leaching to surface and groundwater.

The purpose of this chapter is to provide an understanding of the flow of nutrients on the farm and to help the livestock producer determine if his or her farm:

1. Has a nutrient balance.
2. Has an excess of manure nutrients.
3. Has a shortage of nutrients.

In addition, strategies will be discussed to deal with excess nutrients.

Nutrient Imbalances

Nutrient imbalances can occur on a single field, an individual farm, or on a regional basis.

Single-field nutrient imbalances are common on any livestock farm. Easy access fields, fields close to the barn, loafing areas, and pasture fields often accumulate excess manure nutrients. Spreading manure based on convenience and not the crop’s nutrient requirements may result in excessive nutrient concentrations and water-quality problems.

Individual farm nutrient imbalances. Livestock farms import significant quantities of nutrients as animal feeds. Livestock utilize only 10 to 30% of these nutrients, excreting the remainder as manure. This results in a concentration of nutrients on the livestock farm. This is a common challenge in the Corn Belt states where producers tend to concentrate either on grain production or livestock production.

Regional nutrient imbalances have developed in the past 30 years as livestock/poultry production and feed-grain production have concentrated in specific, but separate, regions of the state and the country. Nutrient excesses on a regional scale involve townships, counties, or multiple counties with high concentrations of livestock or poultry that produce more manure nutrients than the crop base in the geographical area can utilize. Several top livestock-producing areas have accumulated high concentrations of nutrients where more nutrients are available from the manure produced than can be utilized by the crops grown.

The primary question a livestock farmer must ask is: Am I building up nutrients (producing more nutrients than can be utilized on the farm)? To answer this question, the farmer needs to understand the flow of nutrients into the farm, the nutrient needs of the farm, and the flow of nutrients off the farm. The primary nutrients to track for the farm nutrient balance are nitrogen, phosphorus, and potash (N-P₂O₅-K₂O).

The main nutrient inputs on a livestock or poultry farm are commercial fertilizer, purchased feed, animals, irrigation water and rainfall, and legume nitrogen fixation. Figure 3 illustrates the flow of nutrients onto, and off, a farm.

Figure 3. Typical livestock and poultry nutrient flows. Adapted from the Livestock and Poultry Environmental Stewardship curriculum, MidWest Plan Service (MWPS). Used by permission.

Within the boundaries of the farm, a recycling of nutrients occurs between the livestock and the crops. Manure nutrients are recycled, at least in part, for crop production. Feed crop nutrients are recycled as animal feed for livestock or poultry production.

Nutrients exit a livestock operation preferably as managed outputs including animals and crops sold and possibly other products moved off farm (e.g., milk, eggs, or manure sold or given to a neighboring crop producer). Some nutrients exit the farm as losses to the environment (nitrates in groundwater, ammonia volatilized into the atmosphere, and nitrogen and phosphorus into surface water). Nutrients (especially phosphorus) also accumulate in large quantities in the soil. Although not a direct loss to the environment, a growing accumulation of nutrients in the soil adds to the risk of future environmental losses.

Nutrient Inputs – Managed Nutrient Outputs = Losses to Environment

The loss to environment is the difference between the inputs and the managed outputs. This imbalance accounts for both the direct environmental loss and the accumulation of nutrients in the soil. Livestock operations with a significant imbalance are concentrating nutrients, resulting in increased risk to water quality (Lanyon and Beegle, 1993, and Klausner, 1995) and are fundamentally unsustainable. In contrast, livestock farms that have achieved a balance represent a sustainable production system.

The goal of the livestock or poultry operation is to achieve a balance of inputs with managed nutrient outputs. On some farms, a farm nutrient balance can be managed on the farm itself; in other cases, manure needs to be moved to other farms to achieve a nutrient balance.

Evaluating the Whole Farm Nutrient Balance for Livestock or Poultry Operations

There are two primary methods for estimating the whole nutrient balance on your farm.

1. Whole Farm Nutrient Balance review assesses nutrient input content of the feed purchased, the fertilizer purchased, the legume nitrogen produced on the farm, animals purchased, and an estimate of the nutrients added as a result of irrigation and/or rainfall. The second phase of this budget involves estimating the nutrient content of all the nutrients flowing out by way of crops, meat, milk, eggs, animals sold, and manure transported off the farm. This method is scientifically based, but time consuming, and requires extensive records to calculate.
2. A second method provides an easier, but factual, estimate of your whole farm nutrient balance. It involves measuring or estimating total manure nutrient production compared to whole farm crop nutrient utilization. An excess of manure nutrients for crop production suggests a likely whole farm nutrient imbalance. This is the method we will discuss in this chapter.

Estimating Manure Nutrient Content

One of the best ways to determine manure nutrient content is to obtain a manure analysis of the different types of manure produced on the farm. An annual manure analysis should be taken for each different manure storage on the farm. For specifics on sampling procedures and reading laboratory analyses, see Appendices A and B, respectively.

The manure analysis will provide information on the amount of nitrogen, phosphorus, and potash in the manure. For solid manures, the amounts are expressed as pounds of N (nitrogen), P₂O₅ (phosphate), and K₂O (potash) per ton. For liquid manure, the amounts are expressed in pounds of N, P₂O₅, and K₂O per 1,000 gallons of manure.

In addition to knowing the concentration of nutrients, the quantity of the manure that coincides with the respective manure analysis must be determined. For example, a typical manure analysis may indicate 20 lbs of nitrogen (N), 14 lbs of P₂O₅, and 17 lbs of K₂O per 1,000 gallons. If this represents 1 million gallons of manure, then the total nutrient content of the liquid manure is 20,000 lbs of nitrogen, 14,000 lbs of P₂O₅, and 17,000 lbs of K₂O.

Note: Software programs are available at the local USDA, Natural Resources Conservation Service, and Soil and Water Conservation district offices to do Whole Farm Nutrient Budgets.

If manure analyses are not available, a second method to determine manure nutrient content involves using book values to determine volumes of manure and pounds of manure nutrients produced. Table 4 provides estimates of the nutrients and volumes of manure produced for various types of livestock and poultry.

Using Table 4, let’s look at an example for a swine operation with 500 grower-finishers averaging 150 lbs. The manure is stored in an underground pit and handled as a liquid.

Using Tables 5 and 6 to determine nutrient needs, complete the table shown here. (Note: P₂O₅ and K₂O amounts are for crop removal; results from soil tests may vary.)

Marketing of manure creates an additional managed output similar to the sale of crops or livestock products. Several farms throughout Ohio and the United States are now marketing their manure to other farms and for other beneficial uses. Some farms sell their manure based on its nutrient content to other farms needing nutrients. Some livestock and poultry producers have manure-spreading agreements with neighboring farms to apply manure nutrients on their farms at no cost. Still others market their manure products to non-farm individual users as well as commercial firms, such as landscapers. (See Chapter 4, Treatment and Utilization Options for Livestock Manure.)

Strategy 4. Manure treatment.

In some situations, it may be necessary for animal production systems to consider manure-treatment technologies similar to municipal and industrial-waste treatment systems. Some manure-treatment systems focus on disposal of nutrients with modest environmental impact. For example, treatment systems commonly dispose of wastewater nitrogen as a gas (no environmental impact) or ammonia (some environmental impact). Other treatment systems enhance the value of manure (e.g., solids separation or composting) to allow alternative uses of the nutrients. Complementary manure-treatment and manure-marketing strategies can contribute to improved nutrient balance. For example, some producers are successfully combining composting (for odor control and volume reduction) with marketing of manure to crop farms and urban clients.

Strategy 5. Changing crop rotations.

Changing rotations should include crops that can utilize more nutrients such as wheat/straw removed and forage crops compared to corn and soybeans. Corn and soybeans generally use fewer pounds of phosphate and potash per acre than do wheat with straw removed or hay crops.

Table 8 illustrates the additional amounts of phosphate and potash that can be utilized by adding more wheat or hay crops to the farming system. This strategy diversifies the cropping system on the farm and better utilizes nutrients from the manure produced on the farm.