Confined Livestock and Manure Nutrients
The structure of animal agriculture continues to shift toward fewer and larger operations, concentrating livestock in local areas. As a consequence, the utilization and disposal of animal manure from animal feeding operations continues to be an important farm management challenge if producers are to be successful in reducing water quality degradation related to land application of manure. When nutrients are recycled on the land at rates that exceed the capacity of the land to utilize the nutrients, continued manure applications can lead to a buildup of nutrients in the soil. This increases the potential for nutrients to move from the field through leaching and runoff to pollute groundwater and surface water.
- Spiegal, S., et al. "Manuresheds: Advancing nutrient recycling in US agriculture," Agricultural Systems, Volume 182, June 2020.
Estimates of Recoverable and Non-Recoverable Manure Nutrients Based on the Census of Agriculture
This study provides insight into issues associated with the increasing concentration in the confined livestock industry. We inform policy initiatives and policy choices by describing the recoverable manure nutrients, the excess nutrients, and areas with excess nutrients. By describing these changes in indicator variables, we establish an "upper" bound on the reach of policies to manage manure nutrients. In addition, we provide a consistent comprehensive data set for further analysis by NRCS and other natural resource agencies.
This study used data from seven Censuses of Agriculture from 1982 through 2012 to estimate the quantity of recoverable (generally concentrated in a small area) and non-recoverable (generally dispersed over the landscape as with grazing animals) manure nutrients produced by the animal agriculture sector. Using Census inventory and sales data, we estimated manure nutrients based on estimates of the number of animal units, by animal type, for each Census farm. Based on animal numbers and type, farms were classified into groups of no livestock, livestock farms with non-recoverable manure, and two size classifications of livestock farms with recoverable manure; the smaller generally referred to as animal feeding operations (AFOs) and the larger generally referred to as concentrated animal feeding operations (AFO-CAFOs). (CAFOs are defined by the Environmental Protection Agency using animal numbers and farm conditions. We can only estimate the number of AFOs that are potential CAFOs, hence AFO-CAFO.) Estimates of the quantity of manure were based on literature coefficients and the average animal unit numbers per operation.
Costs Associated with Development and Implementation of Comprehensive Nutrient Management Plans
In 1999, the U.S. Department of Agriculture (USDA) and the U.S. Environmental Protection Agency (EPA) released a joint "Unified National Strategy for Animal Feeding Operations"(Strategy), which presented a plan for addressing the potential water quality and public health impacts associated with AFOs. The Strategy recognized the complementary roles to be played by voluntary and regulatory programs. Importantly, the Strategy articulated a national performance expectation that all AFOs should develop and implement technically sound, economically feasible, and site-specific comprehensive nutrient management plans (CNMPs) to minimize potential adverse impacts on water quality and public health, and to accomplish this within a 10-year implementation period.
The Strategy recognized the importance of understanding the costs of nationwide CNMP implementation and called upon EPA and USDA to evaluate costs and benefits. In September 2000, USDA initiated the first phase of an assessment of:
1. The cost of upgrading facilities and practices on AFOs nationwide to meet CNMP technical guidance.
2. The technical assistance needed to plan, design, implement, and follow up on needed structures and practices.
3. The cost of alternatives to land application of manure, including feed management, alternative uses, and treatment options.
This report addresses the first two components of the USDA assessment. Presented here are the findings on the number and distribution of operations potentially needing CNMPs, estimated costs for developing and implementing CNMPs on these operations, and overall cost summaries by region, livestock type, and operation size. A subsequent report will address the cost of alternatives to land application of manure and other strategies to minimize potential nutrient excesses.
Manure Nutrients Relative to the Capacity of Cropland and Pastureland to Assimilate Nutrients
The analysis shows that the structure of animal agriculture has changed dramatically over the last two decades. Small and medium-sized livestock operations have been replaced by large operations at a steady rate. The total number of livestock has remained relatively unchanged, but more livestock are kept in confinement. The number of confined animals per operation has increased for all major livestock types. A significant shift in the mix of livestock types occurred as dairy cattle decreased in number and poultry and swine populations increased. Livestock populations have become more spatially concentrated in high-production areas. The number of animal units per acre of land available on the farm for manure application for the largest operations is often high, averaging more than eight confined animal units per acre for large poultry and fattened cattle operations.
These changes in animal agriculture have resulted in increased problems associated with the utilization and disposal of animal waste. As livestock production has become more spatially concentrated, the amount of manure nutrients relative to the assimilative capacity of land available on farms for application has grown, especially in high production areas. Consequently, off-farm export requirements are increasing. In some counties the production of recoverable manure nutrients exceeds the assimilative capacity of all the cropland and pastureland available for manure application in the county. The number of these counties has significantly increased since 1982, indicating that problems associated with animal waste utilization and disposal have become more widespread over the last two decades as the structure of animal agriculture has shifted toward fewer, but larger livestock operations.
NRCS documents the effects of conservation practices and systems so that better decisions can be made and risk is managed more effectively. NRCS cooperates with other Federal and State agencies and conservation partners to collect and analyze natural resource data.