From ten to twenty tons per acre is considered a sufficient application of barn manure for most farm crops. Larger amounts are sometimes applied to the soil for truck and market garden crops.
Barn manures are applied to the soil by these methods:
The manure is sometimes hauled out from the barn and placed in a large pile in the field or in many small piles where it remains for some time before being spread and plowed or harrowed in.
Some farmers spread it on the field and allow it to lie some time before plowing it in.
It is sometimes spread as soon as hauled to the field and is immediately plowed in or mixed with the soil. This last is the safest and most economical method so far as the manure alone is concerned.
When the manure is left in a large pile it suffers losses due to fermentation and leaching.
At the Cornell University Agricultural Experiment Station, five tons of manure from the cow stable, including three hundred pounds of gypsum which was mixed with it, were exposed in a compact pile out of doors from April 25th to September 22d. The result was as follows:
| April 25. | Sept. 22. | Loss per cent. | |
| Gross weight | 10,000 lbs. | 5,125 lbs. | 49 |
| Nitrogen | 47 lbs. | 28 lbs. | 41 |
| Phos. acid | 32 lbs. | 26 lbs. | 19 |
| Potash | 48 lbs. | 44 lbs. | 8 |
| Value of plant food per ton | $2.29 | $1.06 |
When distributed over the field in small piles and allowed to remain so for some time, losses from fermentation take place, and the rain washes plant food from the pile into the soil under and immediately about it. This results in an uneven distribution of plant food over the field, for when the manure is finally scattered and plowed in, part of the field is fertilized with washed out manure while the soil under and immediately about the location of the various piles is often so strongly fertilized that nothing can grow there unless it be rank, coarse weeds.