Soil Sterilisation

Edifenphos was degraded in flooded soil samples more rapidly than in nonflooded soil at 50% water holding capacity. A Pseudomonas strain utilised edifenphos as the sole carbon source. Soil sterilisation retarded degradation of edifenphos (Rajaram and Sethunathan, 1976). 

Ammonium thiocyanate by itself is not used as a herbicide, although at a rate of 80-100 kg/ha it is suitable for total weed killing. At the same rates, it can be used for defoliation and for temporary soil sterilisation. It is rapidly absorbed both by the roots and the leaves of plants and is translocated. 

At high rates of 1.2-3.5 tons of B20,/ha, all three borates are used pre-and postemergence as total herbicides for soil sterilisation on non-crop sites. At these rates they are suitable also for the eradication of St. John s wort (Litzenberger et al., 1945) and poison ivy (Stodard, 1944). At lower rates of40-100 kg B20j/ha they can also be used for selective weed control in sugar beet and fodder b t (Crafts and Raynor, 1936 Wang and Klotz, 1938 Crafts et al., 1941). 

Due to the small plants and short produetion eyele soil sterilisation is sometimes carried out prior to the produetion of baby leaves. Sterihsation is usually carried out using metam-sodium or dazomet (Basamid) but steam sterihsation is also used. Some growers have also experimented with mulching to suppress weeds and this can work in some situations. 

RAMIREZ-MARTINEZ J.R. and MCLAREN A.D. 1966. Some factors influencing the determination of phosphatase activity in native soils and in soils sterilised by irradiation. Enzymologia, 31 23-38. ... 

Soil sterilisation has proved of particular value for controlling the damping-off diseases which are so destructive to seedlings. It Is also generally" recommended for the prevention of truck-crop diseases , such as scurf, black-rot, and stem-rot of sweet potatoes . Sterilization may be accomplished by drenching the soil with a solution of 1 pint of 37 per cent formaldehyde in 12.5 gallons of water and then co e ing with burlap or paper for... 

In organic systems the number of hours of hand weeding needs to be reduced, as labour, particularly in the developed countries, is expensive. This can be achieved by competition, the timing of cultivations, adaptation of the rotation nutrient management system and by crop density (Kropff, et al., 2000). Barberi, et al. (2002) experimented with a system of soil disinfection using hot steam to sterilise weed seeds. 

Baumann, A., Schimmack, W., Steindl, H. and Bunzl, K. (1996) Association of fallout caesium with soil constituents effect of sterilisation of forest soils by fumigation with chloroform. Radiat. Environ. Biophys., 35, 229-233. 

John Innes composts are a mixture of sterilised loam soil, peat and sand containing various amounts of nutrients and chalk. The nutrients are usually added in the form of a pelleted NPK fertiliser (Osmocote). 

Other measures to improve the penetration of heat to deeper soil levels are the installation of a permanent steam-piping system under the plot (Nederpel, 1979) systems operating under reduced pressure provided by fan action (Runia, 1983) and the use of steam-air mixtures, provided by blowing air into the steam supply (Belker, 1990 Labowsky, 1990). The latter technique permits more control of the temperatures achieved, and is favoured where a soil pasteurisation procedure is desired rather than complete sterilisation. 

Calcium chloride (CaClj) and magnesium chloride (MgClj 6HjO) are sporadically used in the USA at rates of several hundred kg/ha as total weed killers for the sterilisation of soil on industrial sites, on the banks of highways and other non-crop areas. 

Figure 6.2 The Effect of the Possession of Nitrogen-fixing Root Nodules on the Growth of Clover. The plant on the left was grown in sterilised soil, the one on the right in soil containing Rhizobium trifoHL Roots taken from the plant on the right show extensive nodulation.

Indeed examination of many soil bacteria in situ reveals them to be heavily encapsulated. The synthesis of bacterial polysaccharides appears crucial to the maintenance of soil structure and ultimately soil fertility. The coalescence of mineral particles to form aggregates and the resistance of such aggregates to stress is a measure of a soil s stability. Many soil bacteria are able to bind soil particles into aggregates, through the production of extracellular polysaccharides, or by charge interactions. Addition of Azoto-bacter chroococcum or Pseudomonas sp. promotes the stabilisation of sterilised silt loam soils. 

Abiotic control can be used as a negative control using sterile soil. This was obtained by heating up to 500 g of soil in an oven at 125 C for six hours. Then the water lost during sterilisation was restored by using a 0.02 wt% aqueous solution of sodium azide (NaNj) and thoroughly mixing [63]. 

The work of Stacker [65] has demonstrated that a direct measurement of the plant toxicity of biodegradable materials is impossible. Initiated degradation processes in the test trays had caused a dramatically reduced plant growth. Those effects appeared even if natural polymers, such as starch or cellulose were used and even if the soil was sterilised before the test. Tests with not readily biodegradable polymers should be possible since the microorganism community is not activated that much. In such a case ecotoxic effects will most probably be related to an incompatibility of leachable components from the material. That outcome should be considered for the conduction of bioassays with plants and with other test species as well. 

The extremely complex interrelationships that exist in the rhizosphere between detrital processing, mineralisation of organically-bound nutrients and nutrient uptake, makes field investigation of these processes difficult. Consequently, an alternative approach has been to use sterilised soil and added consumer and decomposer organisms (microcosms) in various combinations in the laboratory to investigate the role of the microfauna in the soil P cycle. 

Clear up body fluids promptly and disinfect surfaces appropriately Dispose of all contaminated waste safely according to local guidelines, including how to dispose of soiled linen Clean, disinfect and sterilise equipment as appropriate... 

Chloropicrin was used as a chemical weapon in World War I. In the chemical industry, it is widely used for organic synthesis, and in fumigants, fungicides and insecticides to sterilise soil and seed, and for the extermination of rodents. 

Several authors have used the calorimeter for measurements of metabolic activity in soil [80, 87-99]. One of the difficulties with measurements of natural samples are of course the complexity of the system, in which many physico-chemical reactions may contribute substantially to the measured heat output. By using sterilised soil samples, a contribution of 10% of the total heat output was shown to originate from non-biological reactions [95]. The... 

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