Reducing Environmental Contamination from Feedlot Manure in the South Platte River Basin through Agronomic, Economic, and Social Analysis and Education
1. Determine optimum feedlot manure application rates and accompanying nitrogen (N) fertilizer needs for silage corn and to use the pre-sidedress soil nitrate test and the chlorophyll meter as a guide for in-season N recommendations in manured fields.
2. Determine crop water use and nitrate loss below the root zone as a function of manure application rate and timing.
3. Evaluate the effect of manure rates on soil quality and microbial populations and on pest populations (weeds, diseases, insects) and management recommendations.
4. Compute the costs and returns to alternative management schemes, determine economic returns and constraints for hauling, and understand the decision-making processes and relationships of persons and organizations in the chain from feedlot stocks of manure to potential users of manure as a fertilizer.
1. Change the perception of manure as a waste to its being viewed as a valuable resource and to increase the use of manure credits so that applications will be made at agronomic rates and environmental problems minimized.
2. Encourage feedlot operators to conduct manure testing and to give the nutrient analysis of each load to the recipient.
3. Train manure haulers/spreaders in calibration of their equipment and proper application techniques.
4. Teach consultants, fertilizer dealers, and producers to base fertilizer recommendations on soil testing, manure analysis and calibration, the pre-sidedress soil nitrate test, and chlorophyll meter measurements.
Two corn fields on different private farms were used to measure effects of manure applications on crop growth and soil quality. In both years we used field TB1, a field with clayey soil and no previous history of manure applications. Fields with long histories of manure application were also used; in 1997 we used field JP1, in 1998, RD1. Both of those fields had sandy soils. The fields received four manure treatments (0, 10, 20, and 30 tons per acre fresh weight) and two sidedress nitrogen rates (0 and 50 lbs nitrogen per acre) in the spring of 1998.
Soil and corn plant samples were collected throughout the growing season to provide a picture of nutrient availability, crop water use, and nitrogen dynamics in the soil under different manure rates Weed, disease, and insect populations were measured, as were soil microbial activity and earthworm populations. The 1998 yield and end-of-season soil and plant data are currently being collected and analyzed. In 1997 we found that manure increased yields at TB1 (no previous manure), probably from increased water-holding capacity in a year when water was deficient from weed pressure and sprinkler problems. The field also suffered serious hail damage; it is possible some soil effects from the manure had a positive effect on recovery. Although the field had a lot of nitrogen in the subsoil from previous years’ fertilizer applications, there was no movement of manure-N below a depth of 90 cm in 1997, probably related to the clay content of the soil.
Preliminary results suggest that soil microbial activity increased with application of manure at TB1, but not at RD1; activity at TB1 was generally higher than at RD1. Earthworm populations from spring and fall soil samples were very low; manure effects on earthworm population are not evident.
We have found no significant increases of weeds or corn rootworm from the manure additions at either site. In fact, in 1998, TB1 had a lower proso millet population with increasing amounts of manure. RD1, with a long history of manuring, actually had no weeds in the early growing season. Preliminary data suggest stalk rot occurrence increased with manure application, however, these data have not yet been statistically analyzed. Manure promoted microbial activity at TB1 in the spring of 1998. The two 1998 fields had extreme differences in weed populations. TB1 had ten weed species, nine of which had also appeared in 1997. RD1 had no weed seedlings at the time of sampling; this is probably due to a cover crop of winter wheat and a pre-emergence herbicide applied when the wheat was killed off at planting. This contradicts commonly heard beliefs that manure applications lead to weed problems.
A survey was developed, tested, and implemented that asks farmers their practices, experiences, and views of manure use in crop production. The questionnaire was sent to about 1,100 farmers in mid-November; results will be reported in 1999. Data that were collected on farming operation costs will be used to develop budget scenarios.
Four fact sheets were developed to provide information on manure analysis and recommendations to growers; a fifth one on manure spreader calibration is in press.
Because the field aspects of the project are still underway we cannot yet quantify the benefits from it. We expect that the outcomes will be better optimization of manure applications to plant needs, which should reduce the chances of nitrate leaching into groundwater supplies, and perhaps higher plant yields. Improving manure handling and increasing the perception of it as a high-quality plant food may increase the use of manure, in terms of both numbers of farmers and distance utilized from manure sources.
Reactions from Farmers and Ranchers
Response from wheat farmers regarding using manure to restore eroded soils was generally positive. Their main concern was having access to manure at a reasonable price.
After the 1997 field results were analyzed we met with the growers on whose fields the research had been conducted and presented the results of the season, focusing on each grower’s field. They were extremely interested in the data from their fields and very positive about receiving them. The concept of nitrogen budgeting made a special impact. Data from the research plots and from adjacent areas in the same fields indicate excessive nitrogen use; the growers intend to include nitrogen from manure and irrigation water in their nitrogen budgeting.
We have three growers/feedlot operators who have allowed us to use their corn fields for the research objectives. They and three manure haulers/feedlot operators provide us with information about the business, guide our investigations, and keep us focused on the practical issues.
This summary was prepared by the project coordinator for the 1999 reporting cycle.