Abstract
The objective of this work was to evaluate the efficiency of a new method, developed for predicting density and floristic composition of weed communities in field crops. Based on the use of solaria (100 mm transparent plastic tarps lying on the soil) to stimulate weed seedlings emergence, the method was tested in Tandil, Argentina, from 1998 to 2001. The system involved corn and sunflower in commercial no-till system. Major weeds in the experiments included Digitaria sanguinalis, Setaria verticillata and S. viridis, which accounted for 98% of the weed community in the three years of experiments since 1998. Large numbers of Tagetes minuta, Chenopodium album and Ammi majus were present in 2001. Comparison of weed communities under solaria with communities in field crops indicated that the method is useful for predicting the presence and density of some major weed species, at both high and low densities, of individuals in areas of 10 ha using only five solaria. Low density of weed species makes the method particularly useful to help deciding the time for herbicide applications to avoid soil contamination.
Highlights
No-till sowing has become a common agricultural practice in Argentina during the last decade
S. verticillata and S. viridis comprised more than 90% of weed seedling species, recorded in all experimental sites in 1998 and 1999 in both solaria and untreated crop sections, so they were analyzed as annual grasses
Data of SWD and crop weed density (CWD) from fields with different periods, in which weeds had not formed seeds in previous years (Table 1), showed that weed seedling number of both species decreased, depending on the number of years of avoidance of weed seed return to the soil
Summary
No-till sowing has become a common agricultural practice in Argentina during the last decade. In the 2001/ 2002 cropping season, five million ha, equivalent to 30% of the total area devoted to agricultural production in the country, were cultivated with this technique (Peiretti, 2002). Some examples are: there is no chance to perform inter-row cultivation, when crops are growing; it is impossible to incorporate preplanting herbicides by mechanical means; and the performance of some preemergence herbicides can be affected, because they are retained by crop residues (Locke & Bryson, 1997). In the southeast of Buenos Aires Province, Argentina, no-till sowing of summer crops, under high volume of residues, reduces the efficacy of preemergence herbicides to control
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