Weed infestation in wheat sowings in central and western part of Latvia
Lapins, D.(Latvia Univ. of Agriculture, Jelgava (Latvia). Faculty of Agriculture. Dept. of Soil Management) | Nemaine, I.(Latvia Univ. of Agriculture, Jelgava (Latvia). Faculty of Agriculture. Dept. of Soil Management) | Berzins, A.(Latvia Univ. of Agriculture, Jelgava (Latvia). Faculty of Agriculture. Dept. of Soil Management) | Korolova, J.(Latvia Univ. of Agriculture, Jelgava (Latvia). Faculty of Agriculture. Dept. of Soil Management)
A weed infestation monitoring was carried out annually at the end of July in stationary observed areas in the Jelgava, Dobele, Saldus, Talsi, Tukums and Kuldiga districts of Latvia during 1994-2002. The weed infestation of sowings was determined using quantitative currency method developed by A. Rasins and M. Taurina (1989). The occurrence index was calculated for characterizing separate weed species and groups of weeds. Shannon biological diversity index was used as a complex indicator for weed infestation of sowings. Evaluation of weed infestation monitoring results was done using data ranging and grouping. To characterize dynamics of separate weed species, the index of changes of the number of weed species was used. Fisher criterion was applied for evaluating the influence of herbicides and crop rotation. Dominant weeds (greater than 5 p. mE-2) in winter wheat sowings were Elytrigia repens, Viola spp., Stellaria media, Matricaria perforata, Polygonum spp., and in spring wheat sowings - Elytrigia repens, Lamium purpureum, Stellaria media and Fallopia convolvulus. The number of weed species varied from 13 to 18 during the 5 investigation years.
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