After examining data for various types of livestock and differing management practices in the U.S. In 1939 it was concluded that acceptable values for the recovery of fertilizer constituents in livestock excrement are approximately: nitrogen, 75%; phosphorus, 80%; and potassium, 85%. The recovery of organic matter in the feed averages about 40%. Their data also indicate that of the fertilizer nutrients in the excrement, 40% of the nitrogen, 2% of the phosphorus. and 75% of the potassium are in the urine.
Where animals are grazing and the manure is directly voided on the soil, the nutrients are well conserved but the poor distribution results in the benefit to crops than would be expected based on the quantities involved. In the case of commercial dairy farms, manure is usually voided on concrete floors and hauled to the field daily or at short intervals.
This is one of the most effective ways of conserving the value of manure. Where the manure and litter are allowed to accumulate, partially decompose, and to dry out or to be leached, large losses of nutrients are likely to occur. Ammonia nitrogen may be volatilized on drying and 11 itra te, nitrogen, and potassium are readily leached.