1987-03-03_REPORT - M1977493 - Laserfiche WebLink

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a� K application rates of sawmill wastes and sewage sludge (with replications) was implemented in the spring of 1974 (fig. 1). The design crossed three application rates of sew- age(5, 10 and 20 tons per acre)and one rate of nitrogen(60 �- lb per acre)with two rates of sawdust(4 and 8 tons per acre), ' one rate of wood chips (20 tons per acre) and a control. All plots were uniformly treated with 300 lb of P,OS per Vegetation test plots on rock waste after tiro seasons.As poor acre and received light daily irrigation the first season on- as the vegetation is, the test plots indicate thatfragniented rock is a inuch better growth meduan than tailings. Besides stabil- ly• ring the tailings, the rock eliminates problems of'bloiving and drifting experienced x hen revegetating tailings. Rock also pro- vides a more stable root zone fir trees 5T/ASS 20T/ASS 10T/ASS 60#/AN 20T/AWC 20T/AWC 20T/AWC 20T/AWC Sewage,wood chips good soil amendments Observations of the treatment plots (along with some 5T/ASS 20T/ASS 10T/ASS 60#/AN extrapolation to future behavior) indicated the most eco- (Control) nomical and beneficial soil amendments to be an initial ap- plication of 20 tons per acre of both sewage and wood chips, followed two or three years later by an additional ]0 tons per acre of sewage. 8 8T/ASS T/ASS 2 lOT/ASS 60#/AN Even with the application of 50 tons per acre of organ- ics, inorganic fertilization will be necessary. The reason- ing can be illustrated with a half-life analogy. In the harsh climate at this elevation, the half-life of nitrogen in sew- 5T/ASS 20T/ASS 10T/ASS 60#/AN age sludge might be from two to five years. Twenty tons 4T/ASD 4T/ASD 4T/ASD 4T/ASD of sewage contains roughly 1,600 lb of nitrogen. If half of that were to become available for plant use within two years, the result would be similar to applying 400 lb of ni- Fig. /. Revegetation test plots for testing the feasibility of trogen per acre per year to vegetation requiring only utilizing good waste and sewage sludge to aid revegetation of fragmented rock and tailing growth media. SS = sewage about 60 lb of nitrogen per acre per year. This would be a sludge, SD = sawdust, WC = good chips, N = nitrogen, T/A gross overapplication of nitrogen except for the presence = tons per acre, #/A —pounds per acre.All plots received 300 of wood chips. lb of P205 and light dail' irrigation for germination and estab- Wood chips have a high carbon-to-nitrogen ratio lishment during the first.season.All values are drY weights(one (about 90 to 1). replication shown) Soil organic matter, the desired product, has a carbon- to-nitrogen ratio of about 10 to 1. Microbial decomposi- tion of the wood, therefore, requires large quantities of nitrogen and uses the excess nitrogen from the sewage to As poor as it is, the test plots indicate that the frag- form humus. Thus, much of the excess nitrogen is re- mented rock is actually a much better growth medium for tained in the soil for future plant use and the sewage and vegetation than tailings. Besides stabilizing the tailings, wood chips complement each other. The process allows a the rock eliminates the problems of blowing and drifting significant quantity of nutrients and organic matter to be encountered when revegetating tailings. Rock is also an applied at one time. (Particular care must be taken. Soil ideal mulch. Very little moisture is lost by evaporation microbes easily outcompete plants for nitrogen by immo- from the surfaces of rocks, thereby conserving water in bilizing the nutrient during decomposition. Without suf- the root zone which encourages vegetative growth be- ficient nitrogen for both microbes and plants, vegetation tween rocks. The rock also provides a stable (solid) root will undergo nitrogen deficiency.) zone for trees. Trees grown in tailings might be uprooted by high winds after growing to a height of five or six ft. Another advantage over tailings is the slightly darker col- Adding organics builds mature soil or of the rock. The darker color absorbs more energy from the sun, which increases the temperature of the Applying 40 tons of organics to the rock is a big step "soil" surface. Higher soil temperatures at this elevation toward building a mature soil. A mature soil is pre- increase both the growing-day length and the growing sea- requisite to achieving self-sustaining vegetation. The ap- son. With the very short growing seasons and cold sum- plication of an additional 10 tons of sewage per acre two mer nights, every growing day is important. or three years later, along with good vegetative growth