Soil mixing

Another approach to improving agrochemical detection is to apply more of the active ingredient to increase the initial soil concentration. As mentioned previously, however, one must be careful not to exceed greatly the labeled application rate of the compound as questions may arise as to concentration effects on the observed dissipation. A more common and acceptable approach is to section the upper soil core into smaller depth increments, yielding increased residue concentrations as the total amount of soil mixed with the residues decreases in each processed sample (Table 1). 

Materials and methods. Each species studied was grown in the greenhouse in a growth unit constructed from 10 cm PVC drain pipe and T-fittings, as described previously. The growth units were filled with an artificial soil mix of perlite/coarse sand/coarse vermlculite 3/2/1 by volume. On the second and fifth day of each week four liters of a full strength Peter s Hydro-sol solution plus calcium nitrate (36.7 g/37.8 liters plus 17.0 g Ca(N03 )2 /37.8 liters) were added to each growth... 

Soybean bloassays of root exudates. Four soybean seeds ( Bragg ) were planted In each of 100 12.5 cm plastic pots filled with an artificial soil mix consisting of perlite/coarse sand/coarse vermiculite 3/2/1 by volume. After one week the plants were thinned to two per pot and the treatments were begun. The experimental design was a completely randomized design with 10 replications (pots) per treatment. On the first day of each week each pot was watered with 300 ml effluent from the appropriate growth units. On the fifth day of each week all pots were watered with Peter s Hydro-sol solution with CaCNOj. At other times the pots were watered as needed with tap water. On the second and fifth day of each week the height of the soybeans (base to apical bud) was measured. 

Soybean dry matter production. One week after planting in the pipes, two-hundred-forty 0.7 liter styrofoam cups with four holes in the lower sides of each were filled with a 2 cm layer of pea gravel, then filled to within 1 cm of the top with a 1/1/1 v/v/v mix of perlite, coarse sand and a sandy loam soil. Each cup was planted with three soybean seed ( Centennial or Coker 136 ) previously coated with Nitragin. The seed were covered with 1 cm of soil mix and watered with tap water. 

International Waste Technologies/Geo-Con, Inc., has used a deep soil mixing system to deliver and mix the chemicals with the soil in situ. The system involves mechanical mixing and injection, as shown in Figure 16.16. 

Soil mixing—For lower-permeability soils, soil mixing using tilling for shallow soil or an auger for deeper soil can be used to introduce oxidants to a treatment area. 

As with pH measurements, a specific amount of water or ionic strength adjusting solution is added to soil, mixed, and allowed to stand. For some analyses, the resulting solution is filtered to separate the soil from the liquid. 

It is possible to extract or remove ionic species, both anions and cations, from soil using ion exchange resins. Both anion and cation exchange resins have been used as well as combinations of the two. Resins can be added to the soil and mixed, or they can be contained in a bag (Procedure 11.11), on a strip, or in capsules buried in soil. Mixing resins with soil allows for more intimate contact with soil and with the soil solution. However, one is faced with separation of the resin from soil at the end of some extraction time. Resins in bags, on strips, or as capsules can easily be removed from soil. However, the resins do not have as intimate contact with soil in this procedure. Good relationships between all these methods and standard extraction methods have been obtained and all approaches have found utility in determining the amounts of various ions in soil. 

If staking is required (see facing page, top), put the stake in now to avoid damaging the roots. Set the plant in the hole and backfill the hole with the removed soil, mixed with a bulky soil improver if necessary. 

T0334 Geo-Con, Inc., Shallow Soil Mixing/Thermally Enhanced Vapor Extraction T0363 Harding ESE, Inc., PetroClean Bioremediation System T0372 Hi-Point Industries, Ltd., Oclansorb... 

T0329 General Atomics, Supercritical Water Oxidation T0335 Geo-Con, Inc., Deep Soil Mixing T0344 Geosafe Corporation, In Situ Vitrification... 

T0320 Funderburk Associates, Solidification Process T0336 Geo-Con, Inc., Shallow Soil Mixing... 

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