These experiments on the production of artificial farm manure show that a good grade of well-decomposed manure may be made by composting straw or corn stalks with certain chemicals, provided a sufficient supply of water is added to keep the compost heap moist. The addition of a proper amount of water is essential for the best decomposition of the materials and for the production of the best grade of manure.
Decomposition was found to proceed somewhat faster in the laboratory than in the open, probably because of the more even temperature. The addition of small amounts of soluble nitrogen hastened the decomposition process in the open and also under controlled conditions in the laboratory or greenhouse, but was more effective when applied to composts in the open.
The results obtained in the greenhouse indicate that too much aeration may be very undesirable in the making of artificial manures, decreasing the decomposition processes and causing a considerable loss in nitrogen. A certain degree of aeration, however, is very beneficial in the decomposition of various composts. A proper relationship between the amount of water and the aeration must be established and maintained to secure the best results.
Inoculation of composts with fresh manure, soil, or cultures of molds may speed up the decomposition process. The results of the experiments carried out along this line, however, as reported here, indicate that with an even temperature, optimum moisture conditions and the best aeration, decomposition of composts prepared with various chemical reagents will proceed quite rapidly, and good artificial farm manures may be produced without any inoculation.
It seems very desirable that some reagent supplying soluble nitrogen be employed in preparing composts from straw, corn stalks or other similar materials, in order to hasten the decomposition processes, and permit of the earlier production of a well-decomposed manure. Such a reagent will also increase the fertilizing value of the manure produced because of the nitrogen added. Artificial farm manure may be produced by composting straw and such materials without the addition of any reagents, but the process proceeds much slower and the manure formed is of less value when applied to the soil.
These experiments show that a satisfactory artificial farm manure cannot be produced under average Iowa conditions without the addition of water. The average rainfall in Iowa will not provide sufficient moisture for optimum decomposition in the composts, nor for the production of a good grade of manure. For the production of artificial farm manures from oats straw, the addition of 800 to 1,000 gallons of water per ton of straw is probably the best, giving most nearly optimum conditions of moisture, air and temperature in the compost.
The method suggested in Missouri for composting by the use of a mechanical mixer attached to the thresher proved satisfactory, saving much time and labor in the preparation of the composts. The method involves little expense and is easily followed. When artificial farm manures are to be made on a large scale, it would certainly be desirable to follow the Missouri method.
The tests with various chemicals indicate that any of the reagents used may be employed to advantage in preparing artificial manures. The maintenance of proper moisture and air conditions in the composts is apparently more important than minor variations in the reagents used, provided, of course, that they contain a satisfactory source of soluble nitrogen.
In general the experiments which have been carried out in the open indicate that the production of artificial farm manure from straw or corn stalks is feasible on Iowa farms, provided the farmer is willing to spend the necessary amount of time and effort in preparing the composts. The expense involved need not be large, but, obviously, it will vary considerably according to the particular farm conditions and the equipment available. The cost of production must be kept at a minimum or the manure produced will not give profitable results. The practice of making artificial farm manure cannot be recommended for general farm use, but where conditions are favorable and the facilities are available at little cost, artificial farm manure may be produced which will be equal in value to farm manure and will serve to supplement the inadequate supply of that important fertilizing material
