Agricultural Wastes最新文献

The effect of salts accumulation—a result of effluent recycling and chloride salts addition—in a simulated anaerobic swine lagoon has been studied. Three laboratory scale reactors were used to simulate actual lagoon conditions. The cations Na, K, Ca and Mg were added as chloride salts, and via the sun dried lagoon effluent, to two of the reactors at the concentrations and ratios found in the sun dried effluent. The results indicated that salts accumulations caused similar effects on biological activity, according to a general toxicity model suggested in earlier work. Salts accumulation was expressed as electrical conductivity (EC). Optimum biological activity was obtained at EC values from 5 to 8 mS for the chloride salts and from 25 to 35 mS for the recycled effluent. Effluent recycling thus caused similar effects on biological activity at much higher salts concentrations than the chloride salts, possibly due to cation antagonisms. A direct conclusion is that effluent recycling is feasible in anaerobic swine lagoons and to a much higher degree than was previously thought. From the practical point of view, effluent recycling will minimize lagoon effluent disposal problems and the treatment cost of the wastes produced in swine farms.

A comparison was made between three goat genotypes (100%, 75% and 50% Katjang), 4% NaOH treated and untreated rice straws fed ad libitum, and 4% NaOH treated and untreated dehydrated palm oil sludge (POS) fed at 20 g per kilogram liveweight (LW) per animal per day. A 1 kg supplement of Leucaena leucocephala was fed daily to each animal.

Average total dry matter (DM) intake and LW gain (LWG) was 48·1 g per kilogram liveweight per day and 33·4 g per day, respectively. Alkali treatment increased intake of straw (P< 0·001) and LWG (P < 0·05). Mean DM intake of straw was low, 3·8 g per kilogram liveweight per day. Treated-POS promoted lower gains (P < 0·05) than untreated-POS diets.

Mean apparent digestibility of DM, crude protein, crude fat and neutral detergent fibre was 61·8%, 64·4%, 82·2% and 61·2%, respectively. For most constituents, there were no significant differences in digestibility between alkali treated and untreated diets.

The 100% Katjang gave lower gains (P < 0·01) than crossbred genotypes. There were no signs of mimosine toxicity; mimosine in the Leucaena was 2·96% of DM.

A soil incubation experiment was conducted to determine nitrate N(NO₃−N) accumulation rates and available N (AAN_t) values for stored liquid manures from dairy cattle and swine, various poultry manures and a municipal sewage sludge applied to Norfolk and Cecil soils. Potentially available N (PAN_t) in the manures and sludge was also estimated by chemical tests which included an acid permanganate extraction, weak acid extraction, strong acid extraction and pepsin digestion. The resulting PAN_t values were compared to the AAN_t values from the soil incubation study.

The rates in which NO_3-N accumulated in soils treated with waste were described using first-order kinetics. The rate constants were highest for soils treated with poultry manure which contained high initial concentrations of ammonia N (NH₃-N) and rapidly mineralizable ORG-N. The lowest rate constants were for soils treated with municipal sludge which contained low concentrations of NH₃-N.

Incubation tests showed significant reductions in inorganic N (IN-N) in the first 2 weeks, which suggested immobilization and/or possibly denitrification or NH₃-N volatilization. After 26 weeks' incubation, AAN_t varied with waste type and soil type, being from 40% to 67% of total Kjeldahl N (TKN) applied to a Norfolk sandy soil and from 17% to 38% for a Cecil sandy loam.

Applications of pig slurry were made to pasture at frequent intervals over a 4-year period. Earthworm populations were assessed after the last treatments had been applied. Total numbers—and those of deep-burrowing species—were greater on the high-slurry plots (5528 m³ per hectare) than on controls receiving inorganic fertiliser. Approximately 212 kg per hectare of copper and 150 kg per hectare of zinc were applied by this high rate of slurry.

Nigeria has tremendous agricultural potential particularly in forest resources. Whilst some efforts have been devoted towards tapping the forest resources, substantial evidence shows that forest residues and wood wastes in, for example, sawmills, have not been properly made use of. However, forest products such as fibreboard are being heavily imported in the wake of dwindling foreign exchange earnings. This paper projects the supply of forestry residues and wood wastes and presents ways in which they can be economically used to produce fibreboard in Nigeria. The use of such agricultural waste is called for in other less developed countries demanding an adoption of appropriate technology.

The waste material collected from concrete-lined ponds of a rainbow trout farm was evaluated as a fertilizer, on a strongly acidic and phosphorous deficient soil, in combination with a liming agent. Lucerne was used as the test crop. The trout farm waste was a source of available nitrogen and phosphorus and had a moderate neutralizing capacity. It did not cause changes in the composition of the herbage which would be detrimental to crop growth or grazing animals. The results should encourage the utilization of the waste as a fertilizer, rather than its disposal by discharge to water courses where it may lead to pollution.

Out of 11 different fungi inoculated into short-time acid-pretreated groundnut shells (GNS), only three fungal species, Coprinus, Sclerotium and Sporotrichum pulvurentum, resulted in true protein content increase, up to 10%, in the substrate. Studies with the three fungi on extended-acid and/or steam penetrated GNS substrate did not result in further increase in the true protein content. The results obtained for Coprinus sp. suggested that, for the effective proliferation of this fungus on GNS, no pretreatment(s) other than addition of inorganic nitrogen to the substrate was required. The in vitro OM digestibility of Sclerotium and S. pulvurentum inoculated GNS was similar to that of the respective pretreated GNS controls. However, significant (P ⩽ 0·05) improvement for OM digestibilities in the Coprinus sp. inoculated substrates was observed. Within the Coprinus GNS substrates the differences were not statistically significant. The results suggested that Coprinus sp. is a potential fungus for improving the nutritive value of GNS.

The action of cellulose preparations from Aspergillus niger and Rhizopus sp. strains (4000 U g⁻¹) were tested on cellulose powder, newspaper pulp, rice straw dust, wheat straw dust, cotton stalk dust and sawdust. Both enzymes resulted in saccharification yields around 40% on cellulose powder and around 30% on newspaper pulp, whereas the yields were below 3% for all other materials tested. Different pretreatments of some of the more resistant cellulosic raw materials prior to enzymatic action resulted in slight increases in saccharification yields. The most effective was treatment with 0·5n acid or alkali which resulted in an increase in saccharification yields of the order of three- and four-fold respectively.