WASTES THAT IMPROVE SOIL 879 Straw, Arc Frequently Handled in a Island, Ohio, and Michigan—Have Similar Way

Wastes That

Improve Another general aspect is that in certain areas, rich in good-quality min- eral matter, organic materials alone can be used satisfactorily. Other soils Soil have enough humus and respond best to chemical fertilizers. But great areas Myron S. Anderson of our soils produce best when both organic manures and chemical fertilizers are applied^ not just one or the other. The addition of organic matter to Every gardener and every farmer soil tends to have at least seven bene- can conserve his supply of organic mat- fits: ter and use it to improve the soil. For It makes a heavy soil lighter, more the gardener it means a compost pile; crumbly, and friable—especially im- the farmer may prefer to spread the portant w^here the soil is high in clay, material immediately on the land. as in parts of the Southeast and Mid- Nearly everything that derives from west. tissues of plants and animals can go It holds light soil particles together into the pile, where it rots into a brown and helps anchor them against erosion. or black, pleasant-smelling, life-con- This increases the water-holding ca- taining, and life-giving mixture that pacity of soil in sandy areas, such as are improves the fertility and texture of frequently found in New England, on a soil. the East and Gulf Coasts, and in sec- The raw materials include those tions of California. from farm wastes (straw, spoiled hay, It provides some of the large quan- stalks) or from the processing of farm tities of nitrogen needed by plants. products (like corncobs, cotton motes, It releases nutrients already in soil husks). Garbage from restaurants and by turning them into soluble com- home kitchens makes excellent compounds that can be absorbed by the post. roots of plants. Productive soils, whether used for It permits growth and functioning of ñeld crops or for gardens, often have a micro-organisms. suitable content of organic matter, It furnishes some of all the elements which should be maintained. To do so, essential for plant growth. the farmer uses crop rotations in which It provides micro-elements in more sod-forming crops and barnyard man- readily available condition. ures have a place. The gardener, how- A compost heap is a place of great ever, must solve his problems in other biological activity. The numbers of ways; he usually finds it impractical to bacteria and fungi present become rotate crops and sod covers. Because enormous. Carbohydrate materials, the garden must serve the full growing such as cellulose, are drastically low- season, Httle chance is left for effective ered in quantity, thereby increasing the use of cover crops, and local supplies nitrogen content of the remaining mass of manure arc often nonexistent or ex- of material. Earthworms and other pensive. Composts or prepared ma- small creatures abound; they enhance nures, therefore, appeal especially to the quality of the organic matter, al- the man who tills a small plot. though they reduce somewhat the total 877 878 1950-1951 YEARBOOK OF AGRICULTURE supply. A compost heap to which some The following is a formula for mak- soil is added normally has no objection- ing compost from miscellaneous or- able odors. ganic matter: Organic waste material Soils are so \'aned, and the organic (dry basis), 1,000 pounds (1 cubic wastes differ so greatly in chemical yard) ; ammonium nitrate (33 percent composition and physical character, nitrogen), 20 pounds; superphosphate that we often have only sketchy knowl- (20 percent phosphoric acid), 20 edge of w^hat may be expected from pounds; ground dolomitic limestone, the use of a particular kind of organic 30 pounds. matter under specified conditions. The nitrogen is added primarily to Composting processes are (employed hasten rotting. TPie phosphate im- because straw and many other organic proves the quality of the compost. The wâstes have nitrogen contents ranging limestone neutralizes the acids formed, roughly from 0.5 to 1.0 percent. That because the acid compounds usually means the ratio of carbon to nitrogen retard the rate of decomposition. The ranges from about 80 to 40. The mate- heap of organic materials should be rials normally have relatively large kept moist throughout but should not contents of cellulose, lignin, and other be subjected to much leaching. Turn- carbon compounds. When they are ing, to aerate the heap, is desirable but added to the soil, micro-organisms re- not essential. sponsible for decomposition consume Extensive variations of the formula nutrients, particularly nitrogen. The are possible. When the material has de- materials of low nitrogen content draw^ composed to a point where an organic on the available nitrogen supply of the nitrogen content of 2 to 2.5 percent is soil. At the same time, bacterial bodies, reached, it approximates the freshly which contain a reserve of nitrogen droppc^d manure (dry weight) from and other nutrients for use some time domestic animals, and is suitable for in the future, are being accumulated in general use. the soil. The bacterial cell is likely to contain about 8 percent nitrogen and COMPOSTS ARE USED in many ways, at least 1 percent of phosphoric acid. essentially as a substitute for rotted Myriads of these cells mean the for- barnyard manure. Applications of 3 or mation of a reserve of available plant 4 tons of comjDOst an acre on a dr)'- nutrients in sufficient amount to be of matter basis correspond to farm prac- great importance in materials added tice wdth animal manures. The gar- to the soil. dener places some in a hole w^hen he When a compost heap is started, ani- sets out a tomato plant or a rose bush. mal manures and chemical nutrients When small seeds are planted, a light are sometimes added, but often the mulch of partly rotted compost may be slower course of nature's action is un- used until the ])lants are an inch high ; aided. Frequently it is advantageous to then the excess is raked off and re- add enough of some kind of readily turned to the heap or used other- available nitrogen to bring the carbon- wise. Surface applications of compost nitrogen ratio down to 25 or lower. around many kinds of ornamental Decomposition processes will then act plants are desirable. under proper temperature and mois- Under some circumstances, farmers ture conditions to diminish drastically and gardeners prefer to make their the carbohydrates present and, per- composts in the soil rather than in a haps to a much smaller extent, decom- heap. Corn Belt farmers frequently pose the lignin and other constituents. haul manure directly from the barn to The carbon-nitrogen ratio tends to the field. Sometimes it is allowed to lie stabilize within a range of around 10 to on the ground for a long time. Some- 12, but the compost may be of good times its is plowed under soon after quality before that stage is reached. spreading. Crop residues, including WASTES THAT IMPROVE SOIL 879 straw, arc frequently handled in a Island, Ohio, and Michigan—have similar way. The same principles apply studied comjDosts and issued reports on then as in the heap^ particularly the their use. The emphasis is frequently need for soluble nitrogen during the on the use of such materials as com- early stages of decomposition. ponents of ¡rotting soils and for use on The gardener may spade under gardens and lawns. There is little doubt leaves and household garbage, but about their value as substitutes for ani- enough chemical nitrogen should al- mal manures. ways accompany the organic matter to insure rapid decomposition. When PAPER MILLS dischargii enormous leaves are used, a fertilizer of 10-6-4 quantities of crude lignin, its deriva- grade (that is, the material contains 10 tive's, and ligninlikc materials. percent nitrogen, 6 percent phosphoric The possible use of such products for acid, and 4 percent potash, each con- soil improvement has long been constituent being present in available sidered. Lignin is acidic and has a form) may frequently be used to ad- capacity for holding bases comparable vantage instead of the 5-10-5 grade, to that of good-quality humus or soil which often is used on gardens. organic matter. The Florida Agricultural Experi- The disposal of sulfite liquors, often ment Station prepared composts with used for extraction of the lignin, f)oses water hyacinths, a great nuisance in a problem that offers a challenge to southern waters. The artificial manures paper manufacturers and agricultur- were prepared in difTercrnt ways with ists. The paper manufacturer must dis- vârious reagents. In one case, 42 pose of his lignin with a minimum of pounds of urea (equivalent to about pollution to the stream that furnishes 19 pounds of nitrogen) was added to wâter for his plant and carries away his 10 tons of green plants. The green but waste products. This means that some drained hyacinths contained about 75 of the organic material may be decom- percent moisture. The original weight posed without serving any useful pur- of the material in the compost heap pose, while some goes down the stream was about 5,000 pounds. The added and harms aquatic life. It is hoped that urea would then increase the nitrogen some day byproduct lignin may cr.ase content in the fresh heap by about 0.5 to be a stream-polluting material and percent on a dry basis. becoJTicî useful to agriculture. F. B. Smith and G. D. Thornton, of When cocoa beans are used for the the Florida Agricultural Experiment preparation of theobromine, later to be Station, got a general picture of converted into caffeine, the greater changes within the heap during a ])art of the mass of the beans is left as 4-month period. The percentage of a residue that contains a small amount nitrogen (1.3 at the start) was 1.74 by of ash and about 2 percent of nitrogen. the end of the second month and 2.57 Cannery-waste disposition has long at the end of the fourth; the percent- plagued processors. The water content age of soluble sugars plus polysacchar- is usually high, and large streams are ides (31.2) was'25.4 and 22.7 at the seldom near for rapid disposition. The same stages. At the end of the first, nitrogen content, dry basis, of a num- second, and fourth months molds per ber of the waste materials is relatively gram numbered 5,000, 25,000, and high, at least 2 percent. Composts pre- 300,000; the numbers of bacteria were pared from cannciry wastes should find 3,250,000, 2,300,000, and 76,000,000; a good local market in j^laees v\iierc and the temperature of the heap went high-acre-value vegetables and fruits from 130° F., to 107^ to 118^ are grown. Other State agricultural experiment Tannery wastes are particularly diffi- stations—among them Missouri, Geor- cult to dispose of because they decom- gia, New Jersey, Ninv York, Rhode pose slowly when they are added to 9()27:.>2°--r)i rîT 88o 1950-1951 YEARBOOK OF AGRICULTURE Streams in any quantity. They normally material for local soil improvement. In contain lime and are often used locally one of the nationally known gardions as a substitute for high-grade manures where azaleas are extensively grown, or organic ammoniates. much of the soil is a little too near Citrus waste is utilized in several neutrality for the best growth of the ways. When frosts cause fruit to drop, plants. The manager reports that saw- it may be left under the trees as fc^rti- dust placed in the holes of a transjDlant lizer. Some citrus peel from cânneries is is highly beneficial. The presumption converted into dried cattle feed, but a is that the mild acidity formed on de- great deal of the unprocessed waste is composition is adequate for good transported to nearby pastures to be growth of the azaleas. used partly as feed and partly for soil Commercial preparations of compost improvement. A small amount is con- have appeared on the markets in the verted to a compost before being ap- United States. Various materials are plied to land, especially material for used in their prejâration, mostly of the home garden. initial nitrogen content in excess of Î .2 Spent mushroom soil is a product percent. Hot-fermc^ntation processes from the caves or houses where mush- develop temperatures around 160" F. rooms arc grown. Horse manure, in- in the specially constructed digestion cluding straw used as bedding, is the chambers used. The nitrogen contents common source of organic matter. The of products sold are likely to be below soil selected is of good native fertility, those of most of the so-called organic and the compost has been adjusted ammoniates used in the fertilizer in- to a neutral or slightly alkaline reac- dustry. These products should have tion. The spent material contains ap- somewhat higher nitrogen contents proximately 25 to 30 percent organic than dried but otherwise untreated matter and is highly regarded by animal manures. growers of market-garden crops, par- ScAvage products in limited C[uan- ticularly melons. Some of this compost tities reach the soils of the United is utilized by the producer who may States. In some of the densely popu- also grow garden crops; some is sold lated parts of the world human wastes locally; limited amounts are trans- play an important part in maintaining ported in carload lots for use in gar- soil fertility. The Japanese often use a dens or on lawns or golf courses. system whereby human excreta, col- Sawdust piles dot the landscape in lected in cities or towns, is transported some parts of the United States. Some in watertight containers to the country, times they arc set on fire because i)eople where the materials undergo fermenta- do not know how to make use of them. tion in tanks before use, primarily as a The nitrogen content of pulpwood usu- source of nitrogen. In that way. disease- ally ranges from 0.2 to 0.3 ]:)ercent. The promoting organisms are drastically cellulose range is 55 to 60 percent and reduced in number, but the material lignin around 25 percent. It is appar- would not meet American standards of ent that readily available nitrogen health protection. In China similar should accompany such material when products are collected and sometimes it is added to soil. Rc^search results on dried in the sun before transportation the influence of sawdust on soil are to the country. In India progress has scarce. Tillers of fine-textured soils, been made in the direction of partial however, have found that incorpora- sterilization of the organic raat(TÍals tion of saw^dust with chemical fertilizers through composting, under conditions has greatly improved the physical prop- favorable to hot fermentation. In this erties of the soil. Apple pomace is often way human wastes become less danger- found in the vicinity of sawdust piles. ous to health. The two materials composted together In the United States, the population have been reported as producing good pressure has not developed to a degree WASTES THAT IMPROVE SOIL 881 even closely approaching that in the basis of a population of 150 million^ Orient. Our national and local prob- the plant nutrients in the human lems relative to human wastes are pri- wâstes have been estimated as 1,400 marily those of disposal by means not tons of nitrogen, 450 tons of phosphoric too detrimental to quality of water in acid, and 400 tons of potash daily. streams. In preparing sewage for de- In India, with a population of about livery to streams, large quantities of 400 million, the quantities of solids organic matter are decomposed. In a eliminated by human beings are esti- few cases the gases given oiï^ princi- mated at about 0.1 pound a day, and pally methane and hydrogen, are uti- the plant nutrients present are in lower lized for power. The sewâgc^ sludge percentage than in the United States. from numerous city disposal plants is The utilization of these materials for recovered and applied to soil. This soil improvement has, however, been class of sludge is likely to have about much greater than in the United 50 }jercent organic matter when con- States. G. N. Acharya, chief chemist of sidered on a dry basis. The total nitro- India, has conducted a strong cam- gen content varies, but is likely to be paign for utilization of human wastes around 2 percent. This means about along with all other waste organic 4 percent on an organic-matter basis. products. His instructions to farniers Other nutrient constituents are usually on the proper means of composting for smaller in quantity. development of high temperatures, The effluents of our city and town 150° to 160° F. within the decompos- sewerage plants often discharge the ing mass, have gone a long way toward most valuable portion of plant nutri- reducing health hazards from use of ents into streams because it cannot be human wastes for soil improvement. applied to the land economically. Garbage utilization has been exten- Sewerage irrigation is utilized in sev- sive but often expensive. On farms, eral areas in the West. Results reported home garbage is conventionally used have been favorable, but vegetables to as hog or chicken feed. In cities, collec- be eaten uncooked should not be grown tion of garbage is costly ; sometimes the on land thus irrigated. A New Jersey garbage is used as hog feed and some- State institution discharges effluent times for soil improvement. More fre- wâters from its disposal plant on a large quently it is discarded as waste. area of sandy farm land. Excellent field crops are grown there with modest ap- THE CITY administration of Miami, plications of commercial fertilizers. Fla., after a study of the Beccari hot- A substantial portion of the nitrogen fermentation process, had engineers de- of sewage can be used for the prepara- sign a plant like one in Gannes, France. tion of high-nitrogen organic fertilizer, The French plant has been in operation but such recovery has not been re- nearly continuously since 1927. The garded as economic under most condi- garbage of a city of 60,000 population tions. Lawn keepers in many ]:iarts of is converted into compost or humus. the United States are familiar with a The process is identified as "an aero- product of this kind from city plants. bic oxidation process of fermentation," The nitrogen content is as high as 6 meaning that the bacteria live in the percent, and the material is sometimes presence of oxygen and create an end treated so as to be sterilized adequately product that is of commercial value as during preparation to render it safe a low-grade nitrogen-carrying humus for use. material. The process requires about A leading journal concerned with 20 days. The material in the storage sewage and sewage products estimates cell reaches a temperature of 160° to a daily per capita (elimination of about 170° F., which destroys all pathogenic 0.15 pound of matter, on a dry-weight organisms and produces a product suf- basis, in the United States. On the ficiently aseptic for general garden 882 19 5 0-1951 YEARBOOK OF AGRICULTURE uses. It is also free from weed seeds. million dollars, on a w^holesale basis. The process is odorless. Only water va- About 75 percent of the amount is for por and carbon dioxide are given off. imported goods of sphagnum moss The Ik^ccari process has undergone origin, and 25 percent is for domestic many variations for adaptation to dif- peat or muck, mostly derived from reed ferent conditions in the United States and sedge plants. Experimental work and in other parts of the world. The has not proceeded to a stage wherc^ it is success of such a process necessarily de- always possible to make an intelligent ]:ends primarily upon the rate at which selection of peat on the basis of botan- nonnitrogenous organic matter is de- ical origin. The user of peat as a con- composed and the nitrogen content of stituent of general potting soil is usually the n^sidue correspondingly increased. not too particular about its acid Experimental data along this line are reaction, but growers of the acid-loving ncxided. plants, such as azaleas, want to be Peat used alone as a substitute for sure that the peat is acid enough, compost or animal manure usually perhaps pH 4.5. givi^s disappointing results. The Ohio Crop residues and farm manures Agricultural Experiment Station constitute the really large sources of found, however, that the addition of a farm-was te materials used for soil im- little barnyard manure or compost provement. Roots, stubble, and other (even as little as one-twentieth of the crop residues in relation to quantities volume of the mixture) produces good of harvested crops vary widely with results in growing greenhouse plants. kind of crop and often wâth method of Peat was also found to be valuable as harvesting. A first approximation in- a constituent of composts w^hen other dicates that probably as much organic organic materials are present. matter remains in the field from pro- Peat, properly used, is of value to duction of an average crop as is re- growers of many kinds of plants. Ways moved in the harvested portion. If all that it may be used include : of the material voided by farm animals Mixed with small amounts of ma- were returned to the soil, it would nure, it may be applied directly, or mean utilization of about 65 percent composts may be made with it. of the portion consumed. Unfortu- Worked into about 4 inches of top- nately, only a minor part of the farm soil at the time of establishing a lawn, manures produced effectively reach the greater penetration of roots may be land. One estimate made in the De- expected. partment of Agriculture indicates that Used as a mulch for shrubbery, bet- 1,370 million tons of manure are pro- ter moisture conditions are provided. duced annually. Only 208 million tons, Applied in seedbeds of shade-grown or 15 percent, is utilized by application tobacco, greater usefulness of added to harvested cro]3s. The nutrient con- fertilizers is said to be obtained. tent of the utilized manure is estimated Cuttings of certain kinds of trees and as follows: Nitrogen, 1,300,000 tons; shrubs root better in peat than in sand. phosphoric acid, 796,000 tons; and Seed germination in peat is fre- potash, 1,102,000 tons. quently better than in soil. Peat may be used to advantage in MYRON S. ANDERSON was tramed at many ways in a small garden or green- Simpson Colleiê av,d Iowa Stale Col- house. It may, however, prove disap- lege. Since comiui^ to the Depariment pointing unless its place in the garden of Agriculiiiie in 1917^ he has worked program is adequately understood. on various chemical problems of soils Dried and ground peat is used as a and fertilizers. Dr. Anderson is a conditioner in commercial fertilizers. senior chemist in the Bureau of Plant The current annual expenditure for Industry, Soils, and Agricultural En- peat in the United States is about 4 <Âneerinii.