Many of the dairies in California’s Central Valley use a water flush system for manure handling; the manure water is eventually mixed with freshwater and applied to cropland during irrigation. Good performance during irrigation applications is important due to the nutrients in the manure water. This project evaluated alternative management techniques (furrow torpedoes, surge irrigation and shortening furrow lengths) for improving irrigation practices on dairies. All three techniques reduced the amount of water required for irrigation. The project also investigated the impact of changing the timing of manure-water additions to the fresh irrigation water. Delaying the addition of manure water until the advancing fresh irrigation water had reached approximately 80% of the distance down the field improved nutrient-application uniformity and reduced nutrient applications.
As California’s dairy industry continues to grow, manure management has become an increasingly important issue for dairy producers, government regulators and the public living in close proximity to dairies. Dairies are increasingly required to prepare nutrient management plans and comply with regulations concerning their manure management practices. A common dairy practice in California is to house the cows in free stall barns with water flush systems to remove the manure.
The manure flush water, high in nutrients such as nitrogen and phosphorus, is collected in holding ponds until it can be combined with freshwater and applied to cropland during irrigation. Being able to quantify the amount of manure water applied is critical to good nutrient management of crops. The high trash and debris content of manure water has precluded the use of most flow meters commonly used in agriculture, such as the propeller meter. A field test of electromagnetic flow meters and a Doppler flow meter determined that both were accurate, dependable and appropriate for measuring manure-water flow rates. Their drawbacks are price ($3,000 to $4,000) and the need for electrical power for permanent flow-meter installations.