THE MAKING OF ARTIFICIAL FARMYARD MANURE.

New Zealand Journal of Agriculture, Volume XXX, Issue 2, 20 February 1925, Page 91

THE MAKING OF ARTIFICIAL FARMYARD MANURE.

TRIALS AT LINCOLN.

M. J. SCOTT,

B.A. (Cantab.), B.Sc., A.1.C., Canterbury Agricultural College,

Lincoln

While the efficacy of farmyard manure has been variously attributed to its manurial constituents, its colour-producing - capacity and consequent warming, its water-holding capacity, its mechanical effect, &c., there appears to be no doubt that its most useful feature in the soil is the giving-off of gas by the action of bacteria which feed on it. Just as yeast feeding on the sugars in dough gives off a gas (carbon dioxide) which causes the bread to rise, so bacteria with an abundant supply of •organic matter give off the same gas in the soil, thus aerating it. Further, experience has shown that farmyard manure has a very decided value, and in pre-war England 35,000,000 tons of it were used annually. With the advent of motors and the war demand on pasture lands for the production of cereals, and the consequent decline in the production •of fat beef, a considerable falling-off in output of this manure resulted —so much so that the Food Ministry, realizing its economic importance, were at pains to find a means of supplementing the supply.' Dr. Hutchison, of the Rothamsted Experimental Station, was able to demonstrate that the bacteria which decompose organic matter in. the soil were distributed everywhere, and required for growth only moisture and adequate food-supply. ' • Since 1919 artificial farmyard manure has been made at Rothamsted and used on various crops. In no case did the yields therefrom differ materially from those obtained from the use of bullock-made dung. This being so, sufficient encouragement. from the farming community was forthcoming to warrant the formation of a syndicate consisting of the original investigators and others, calling themselves the Agricultural Development Company (A.D.C.0.), for the making of artificial farmyard manure on a large scale. The process of making, or perhaps the chemicals used for treating the straw, have been patented in England,

America, and elsewhere, but not in New Zealand so far as the writer knows. ■ '

In 1921 the writer, then at Rothamsted, was greatly impressed with this process of rotting down straw. Knowing the condition of affairs in Canterbury, where straw is commonly burnt, stock not housed, and farmyard manure consequently not made, he could not help thinking that here was a proposition that sooner or later must commend itself to those of our farmers who want’ to maintain the life of their soil. Having subsequently returned to New Zealand, obviously the first thing to be done was to find out if straw would rot in three months under local conditions, and with this in view an attempt was made at the College in January, 1924. We tried six stacks in alltwo of wheat, two of oats, one of barley, and one of grass —containing a total of about 70 tons. A 2-J-horse-power Blackstone'engine and pump that delivered from 600 to 900 gallons of water per hour was used. The water was pumped through 2 in. pipes to the middle of the top of the stack, and then distributed in a series of jets through | in. holes evenly spaced along a pipe lying on the stack. This pipe was movable, and wet the stack to a distance of 4 ft. to 6 ft. on either side of it. It was moved every half hour or so in order to wet the stack as evenly as possible. As a source of nitrogen, ammonium sulphate was used, and, when in sufficient quantity, appeared to be quite satisfactory. The amount of water to be used seems a fairly variable quantity locally, owing to the enormous evaporation which takes place in. northwest weather. We pumped somewhere between 800 and 1,200 gallons per ton of dry straw. This was done at about fortnightly intervals, pumping always until the run-back —collected in a hole by a drain round the stackwas nearly equal to the capacity of the pump. The greatest difficulty we had to encounter was getting the stack uniformly wet; Particularly was this so on the old stacks (two-year-old), which, built to keep the water out, invariably felted somewhere below the surface and were quite waterproof. There was. no difficulty with newly built stacks, which wetted ■ uniformly and rotted completely. To overcome the felting we punched holes in the stack with a long pipe. If such holes are put in on a slant they distribute the waier quite well, but if vertical the water merely runs down them to the ground and wets a column of straw only about 6 in. to 12 in. in diameter. - When the rotting is satisfactory the stack loses its stack-like form and becomes just a manure-heap, and sinks till it is about one-third of the original height. We considered the straw sufficiently rotten when it was of a rich dark-brown colour and breakable by ’twisting a large handful. It is not difficult to see how the stack is wetting by an inspection of the top. Ridges appear where there is dry straw underneath. The temperature rises to between 65° and 75 0 C. —too hot to place one's hand in the material. It would be advantageous if it could be kept lower, as a great deal of soft tissue is destroyed at such temperatures and the fibrous parts of straw remain as a stringy mass. . Of the six stacks, three and a half rotted sufficiently to be carted out- — barley stack, one and a half of the wheat stacks, and half of each of the oat stacks. Everything rotted that had enough water, but the difficulty of. wetting the material throughout was not easily overcome. The grass stack was not persevered with. Wheat or oat straw when crushed splits and allows the water to get inside,. where. it

is absorbed by the pith. Grass-straw does not split in this way, and consequently no amount of wetting would cause it to absorb any quantity of water. In all we expected between 250 and 280 tons of farmyard manure, and we carted out about' 180 tons. As already stated, operations were commenced in January, and the dung was ploughed under in June last, being applied at the rate of 60 to 70 loads, equivalent to 25 to 30 tons, per acre. Strips were left unmanured, the plan being to estimate the effect of the manure on the yield of mangolds. Results will be recorded later, after harvesting of the crop. Whether this process will develop or not is entirely a matter of cost, and that aspect is being investigated. At present we are satisfied that the straw rots satisfactorily if the right conditions for bacterial growth are obtained.