A development of the 20th-century Agribusiness age, liquid manure is used as an alternative to fermented manure. Manure in both forms is used as a nutrient-enriched fertilizer for plants, because farm animals excrete most of the nitrogen, phosphorus, and potassium that is present in the food they consume.
History
, an archaeobotanist at the University of Oxford, suspects that even as early as the Stone Age farmers had noticed the improved fertility of manured land. Her team investigated European digs for crops of cereals such as wheat and barley, as well as pulses such as peas and lentils. Modern-day scholars think that the Babylonian Chronicles and Egyptian hieroglyphs report manuring practices, while Pliny the Elder and Seneca the Younger describe similar Roman and barbarous Teuton practices. The Sallows photograph in the Gallery shows a rear three-quarter view of a farmer driving a team of horses pulling a manure spreader in Huron County, Ontario. The photograph in front of a barn shows how people in Iowa preserved the fertility of their land. A manure spreader is loaded and operated, which was not a usual or necessary practice on American farms of that era. No farmer had enough barnyard manure for all his tillage. This operator, however, puts all he has on the land and believes that it is worth his while to do so, since it acts to make a good crop better. A gussied-up John Deere horse drawn manure spreader, located on display at Canton Power Equipment in 2012, is shown in the full-colour modern digital photograph. Current American fertilizer practice is relatively recent and dates back to the Post–World War II economic expansion era, when petroleum first began to be applied to agriculture. Once powerful internal combustion engines, such as the diesel 4-cylinder 105 horse-power contained in the Fendttractor depicted in the gallery, allowed farmers to haul heavy steel tanks on twin-axle trailers rated for five metric tonnes around their fields, to liquefy the unfermented manure became feasible and a new commodity was born. As shown in the headline photograph from a 2009 Belgian trade show, liquid manure allows placement near the plant root and makes for a more efficient process. Of course, this necessitates large on-farm storage tanks, as seen at the end of the gallery. By 2016, the hire of professional liquid manure applicators was commonplace, at least in Manitoba. The professional liquid manure spreaders had expensive professional liquid manure spreading equipment, and they were regulated by government to meet a rigorous set of standards. A professor said that for large livestock operations, "to rent the services of manure management planners and custom applicators" was most efficient, and any livestock facility with more than 300 animals must file an updated annual manure management plan with the regulator. Another fellow made nice coin on extracting phosphorus and nitrogen from liquid manure. He proposed the use of centrifuges to concentrate the nutrients.
Gallery
Role in disease transmission
Since at least 1982, health authorities have recognised that the organism, which has been responsible for significant numbers of human deaths, spreads through fecal transmission. The strain's low infectious dose, survival under adverse conditions, and potential for extreme disease severity prompt scientific attention. Radish, alfalfa sprouts, green onions as well as leafy green vegetables like lettuce, spinach are prone to be disease vectors, particularly when they are exposed to the pathogen just prior to harvest. In 1998, the Food and Drug Administration published the Guide to Minimize Microbial Food Safety Hazards for Fresh Fruits and Vegetables. Particular attention is paid to CAFOs because they are the source of most of the liquid manure that is spread on fields of vegetables. Rainwater runoff from these CAFOs was identified in the fatal Walkerton E. coli outbreak as the contaminant of municipal wellwater used for human consumption. Because of the relative infancy of industrial-scale vegetable fertilization by liquid manure, the process had not yet been nailed down by the year 2007, and included:
