Manure Harvesting Rates

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Typically, feedlots remove surface manure once every 6 months. We wanted to see if more frequent manure harvesting from feedlot surfaces was beneficial in reducing ammonia emissions.

The Problem
Background
Experimental Method
Results and Cost Analysis
The Solution

The Problem

Typically feedlots remove pen surface manure approximately once every six months when pen turnover occurs (one group of cattle leaves the lot for slaughter and another comes in). It is typically thought that more frequent manure harvesting is not necessary and creates more labor and animal stress since cattle are not removed from the pen prior to manure scraping. However, since ammonia volatilization occurs on an ongoing basis in cattle pens, and more manure equals more ammonia emissions, increasing the rate at which manure is removed from pens may aid in reducing ammonia emissions from feedlot pens.

Background

The greatest ammonia emissions from feedlots occur from the surface of open drylot pens. Between 50 and 55% of the total N fed to feedlot cattle can be lost to the atmosphere as ammonia (34, 48). Bierman et al. (34) reported that 57 to 67% of the total nitrogen excreted is volatilized by the time that feedlot pens are cleaned, which is typically every 6 to 12 months. By increasing the rate of manure removal from feedlot pens this total volatilization rate could possibly be reduced. However, typical management doesn’t allow for complete removal of manure while cattle are still in the pens. Rather manure is piled in the center of the pen in packed mounds or loose stockpiles. By scraping pens on a monthly basis and mounding the manure in the pens, it might be possible to reduce ammonia emissions from the pens. Our objective is to track ammonia emissions over time with a monthly scraping routine.

Experimental Method

Method. The two treatments for this BMP evaluation are 1) typical scrape rate (control) of every 6 months (no scraping during the treatment period) (CON), and 2) an increased manure scrape rate (once monthly) (INC) in feedlot pens. The treatments will begin with clean pens and fresh cattle. Groups will be of the same size and gender. Pens will be sampled prior to the introduction of cattle to obtain a baseline ammonia emission rate for each pen.

Results and Cost Analysis

Results. Coming Fall 2008......

Cost Analysis. Coming Fall 2008.....

The Solution