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Title: Incorporation of tracers and dazomet by rotary tillers and a spading machine
Author: Juzwik, J.; Stenlund, D. L.; Allmaras, R.R.; Copeland, S. M.; McRoberts, R. E.
Publication: Soil & Tillage Research 41:237-248
Key Words: Pesticide incorporation, Rotary tillers, Spading machine, Fumigation
Abstract: Soil fumigant efficacy in forest-tree and ornamental nurseries depends on the tillage tool used for incorporation. Maximum depth and uniformity of incorporation of surface applied materials by three rotary tillers and a spading machine were compared in a loamy sand nursery using ceramic-sphere tracers (1-3 mm diameter) and dazomet (tetrahydro-3,5,dimethyl-2H-1,3,5-thiadiazone-2-thione) micro-granules. Depth of incorporation in the top 30cm of soil was evaluated by (1) recovery of incorporated spheres in 2cm increments, (2) biocidal activity in 6cm increments, and (3) cone resistance by 1.5cm increments to 45cm. Uniformity of incorporation was evaluated by sphere recovery and biocidal activity. Depths above which more than 95% of the spheres were recovered for the four implements were: 12.5cm, Kuhn and Fobro rotary tillers; 17cm, Northwest rotary tiller; 21cm, Gramegna spading machine. The spading machine produced a distribution of spheres through the soil profile closest to a uniform distribution compared with that produced by the three rotary tillers. Lettuce seed (Lactuca sativa L.) germination was inhibited in the upper 12cm in low and high dazomet rate treatments, indicating that all four implements effectively incorporated dazomet into that zone. Maximum depth (24cm) for total inhibition of germination was observed for the spading machine regardless of chemical rate. Cone index values showed the following maximum penetration: 14cm, Fobro rotary tiller; 22cm, Kuhn and Northwest rotary tillers; 27cm, spading machine. All three measures of depth show a distinct superiority of the spading machine when the chemical fumigant must reach depths greater than 18cm. Within transects across the width of the implement, variations of sphere counts among 5cm³ volumes were much larger for the rotary tillers than for the spade machine.
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