APPLICATION OF SWINE LAGOON WATER TO ALFALFA

摘要

Many large swine production facilities are faced with the dilemma of producing more animal manure than there is land available for distribution at agronomic rates. Most facilities apply manure to field areas with a continuous corn cropping system which limits application timing by traditional ground applicators to spring or fall time periods. Alfalfa represents a crop that utilizes a large amount of nitrogen, has a deep rooting system to aid in recovering nutrients that may bypass the root zones of other crops, and provides a large window for application. Sprinkler irrigation systems allow lagoon water to be spoon-fed during the growing season when soil water holding capacity exists and plant needs are greatest The goal of this study was to determine how much nitrogen could be applied to sprinkler irrigated alfalfa without resulting in excessive nitrogen leaching losses. A line-source irrigation system was used to apply swine lagoon water from an anaerobic lagoon at rates from 0 to 630 kg-N ha~(-1). Lagoon water was supplemented with fresh water from an irrigation well. Alfalfa was harvested 3x, 4x, or 5x times per year. Soil plant, and water samples were analyzed for nitrogen content to determine nitrogen concentrations during the 1994 growing season. Dry matter yield, and N harvest, increased linearly with lagoon water application rate with the highest N harvest of nearly 900 kg-N ha~(-1) when lagoon water N application exceeded 505 kg-N ha~(-1) in the 4x and 5x harvest timings. Lagoon water applications above about 235 kg-N ha~(-1) caused soil water nitrate concentrations to rise above the safe drinking water level of 10 mg L~(-1). Fall soil nitrate and soil water nitrate concentrations tended to rise sharply at the 380 kg-N ha~(-1) level indicating that plant uptake was near the maximum level. The results indicate the potential for application of swine lagoon water N at rates substantially greater than for com without water quality problems.