Formulation of Environmentally Sound Waste Mixtures for Land Application

Major impediments to the land application of coal combustion byproducts (fly ash) for crop fertilization have been the presence of heavy metals and their relatively low and imbalanced essential nutrient concentration. Although nutrient deficiencies, in particular N, P, and K, may be readily augmented by adding organic wastes such as sewage sludge and animal manure, the indiscriminate application of mixtures to crops can cause excessive soil alkalinity, imbalanced nutrition (P, Mg), phytotoxicities (B, Mn, ammonia, nitrite), and unspecified contamination of the food chain by elements such as As. In this study, nutrient availability data and linear programming (LP) were used to solve these problems by formulating fly ash-biosolid triple mixtures which complied with both plant and soil fertilization requirements, and met existing U.S.A. environmental regulations for total As application in sewage sludge (EPA-503). Thirteen different fly ash samples were LP-formulated with sewage sludge, poultry manure, CaCO₃, and KCl to yield 13 unique mixtures, which were then evaluated in greenhouse pot experiments. Results indicated that normal growth and balanced nutrition of sorghum (Sorghumbicolor L.) and soybean (Glycine max (L.) Merr.) crops were achieved in all mixtures, comparable to a balanced fertilizer reference treatment, and significantly better than the untreated control. Phytotoxic levels of B, NH₃, NO₂ ^-, overliming problems, and excessive As levels which were previously encountered from indiscriminate use of these waste materials, were all well controlled by LP-formulated mixtures. Most fly ash quantities in mixtures were limited by either available B (< 4 kg ha^-1) or total As (< 2 kg ha^-1) restrictions during formulation, while the most alkaline fly ash was limited by its high calcium carbonate equivalence (CCE = 53.9%). These results confirmed that fly ash land application should not be at arbitrary fixed rates, but should be variable, depending on the soil, crop, and particularly the fly ash chemistry.     

Heat stress: A major contributor to poor animal welfare associated with long-haul live export voyages

Recent investigations by the Australian Department of Agriculture, Fisheries and Forestry into high mortalities on live export voyages from Australia to the Middle East during the Northern hemisphere summer suggest that animal welfare may be compromised by heat stress. The live export industry has generated a computer model that aims to assess the risk of heat stress and to contain mortality levels on live export ships below certain arbitrary limits. Although the model must be complied with under Australian law, it is not currently available for independent scientific scrutiny, and there is concern that model and the mandated space allowances are inadequate. This review appraises the relevant literature on heat stress in sheep and cattle, including laboratory studies aimed at mimicking the ambient temperatures and humidity levels likely to be encountered on live export voyages. Animal welfare is likely to be very poor as a result of heat stress in some shipments.     

Artemia prey size and mode of presentation: Effects on the survival and growth of phyllosoma larvae of southern rock lobster (Jasus edwardsii)

Performance of phyllosoma of thesouthern rock lobster (Jasus edwardsii)was examined after feeding Artemia-baseddiets. Survival and growth of newly-hatchedlarvae cultured to Stage III were lower(p < 0.05) when fed 0.8 mm Artemia than1.5 mm or 2.5 mm Artemia alone or 1.5 mmArtemia in combination with pieces ofmussel (Mytilus edulis planulatus) gonad.This could not be attributed to deficiencies inthe composition of fatty acids but appeared tobe due to the inability of larvae to capturesufficient appropriate-sized, enrichedArtemia for their nutritional requirements.There was an indication that survival andgrowth were higher between Stages III and Vwhen fed 2.5 mm Artemia than 1.5 mmArtemia alone or in combination with musselpieces. However, Stage VI larvae grew to asimilar size at Stage VIII when fed 1.5 mm or2.5 mm Artemia. Unexpectedly, larvae fedthe combination of 1.5 mm Artemia plusmussel supplement had lower survival than foundpreviously, and generally lower than when fed 1.5 mm Artemia alone. This was despitean apparent nutritional profile (lipid contentand fatty acid composition) of mussel more akinto that of newly-hatched phyllosoma thanenriched Artemia. On the other hand,survival and growth to Stage VIII were higherwhen larvae were fed alginate pelletscontaining Artemia than when fed 1.5 mmor 2.5 mm Artemia alone.     

Indices of soil nitrogen availability for an ecological site classification of British forests

An adequate supply of nitrogen (N) is essential for the successful establishment and sustainable productivity of forest stands. N deficits may necessitate the use of artificial fertilisers. Availability of N in the inorganic forms, and the relative abundance of the NO₃-N and NH₄-N components, influences the species composition of natural forest vegetation. Hence it is essential to use reliable measures of soil N supply that fully reflect its ecological significance. The new Ecological Site Classification (ESC) used in British forestry employs a multi-factorial definition of soil nutrient regime (SNR), including soil N. To develop this, a soil and vegetation study was made at 89 forest sites throughout Great Britain covering the major soil types used for forestry. “Total N” levels were compared with separate pre- and post-incubation measures of the two inorganic N components as potential indices of soil N supply. Multivariate statistical analysis showed that the major discriminant chemical variables for the sampled soils were pH, calcium and NO₃-N and that these were also the main variables influencing the species composition of the ground vegetation. Total N and NH₄-N were less effective discriminant variables for these sites. In some infertile soils the levels of NH₄-N or total N may be of greater importance, as NO₃-N is usually in very limited supply. A multivariate gradient of SNR, which incorporates the NO₃-N measures, has been adopted for use within the ESC system. The position of a site on this gradient can be estimated quantitatively from soil type, ground vegetation species composition and humus type. This enables soil N supply and overall SNR to be assessed in a simple but effective way that guides the operational management of British forest soils for sustainable productivity. It will also be possible to use these techniques to monitor the nutritional status of forest sites over time.     

Sulfur metabolism in Allium cepa is hardly affected by chloride and sulfate salinity

Salinity as a major agricultural problem can affect crop growth and quality. Onion (Allium cepa L.) plant contains a wide variety of sulfur-containing compounds which may be involved in plant protection against salt stress. In the current study, a similar reduction in growth caused by chloride and sulfate salts was observed when onion was exposed to equimolar concentrations of Na⁺. Also, no difference was observed for shoot/root ratio and dry matter content of roots and shoots. Plants accumulated Na⁺ and the respective anions (chloride and sulfate) which in turn caused changes in the content of other nutrients. The content of potassium and calcium was decreased more than the other elements by both sodium salts. Sulfate salinity resulted in substantial increase in total sulfur and sulfate content but chloride salinity affected neither the total sulfur nor sulfate content of the roots and shoots, only in onion exposed to 200 mM chloride salt, those of roots and shoots were reduced. Furthermore, the water-soluble non-protein thiol content as well as the content of alliin remained rather unaffected. In conclusion, either salts affected the uptake and distribution of sulfate in onion, but had no or only a minor effect on the plant sulfur metabolism.     

Legume residue influence arbuscular mycorrhizal colonisation and P uptake by wheat

Legumes have been shown to increase growth and P uptake of the following cereal. This could, in part, be due to nutrients released by the decomposing legume residues. To investigate the effect of P added with legume residues on wheat growth, P uptake and arbuscular mycorrhizal (AM) colonisation, a number of experiments were conducted with different legume residues added to a soil with low P availability under conditions in which N was not limiting. Young and mature faba bean shoots (FYS, FMS) and mature chickpea shoots (CP) were added to soil at different rates (0.5–2%, w/w) with the P concentration being the greatest in the young faba bean shoots and least in the mature chickpea residues. Other treatments included addition of inorganic P at different rates (0–80 mg P kg⁻¹). Available P, growth and P uptake and AM colonisation of wheat were measured after 6 weeks. As expected, inorganic P addition increased growth and P uptake but decreased AM colonisation. The effect of the residues was more complex. AM colonisation was not correlated with available P in the soil amended with residues, whereas there was significant negative correlation between available P and AM colonisation in the treatments with inorganic P. Addition of FYS increased wheat shoot growth and P uptake and decreased AM colonisation. However, FMS and CP addition not only decreased wheat growth and P uptake but also AM colonisation despite low soil P availability. It is concluded that addition of some legume residues can improve the growth of subsequent cereals, but others have a negative effect on wheat growth and AM colonisation which cannot be explained solely by soil P availability.