Revista Brasileira De Herbicidas 2020; 19(3): 1-6
VIABILITY OF WEED SEEDS IN VARZEA SOIL WITH IRRIGATED RICE
The soil weed seed bank is very dynamic and affected by several soil, plant management factors and environmental conditions. In this study, the immediate viability of weed seed germination in floodplain cultivated with flooded rice. Three depths of soil were used: 0-10 cm, 10-20 cm and 20-40 cm. In laboratory conditions, 800g of soil from each depth in five replications were placed in 20 cm high cut pet bottles, and subsequently placed in an incubator at 25ºC with 12 hours of photoperiod. The moisture content of the soil was monitored for weight loss, and when necessary, water was added. The experiment lasted 63 days with weekly counting and identification of emerged weeds. Four weed species were observed: ryegrass (Lolium multiflorum Lam.), malta cross (Ludwigia longifolia DC.), green carpet (Callitriche deflexa Engelm) and red rice (Oriza sativa L.). The emergence of plants was greater in the 0-10 cm depth until 42 days. There was dominance in the emergence of Callitriche deflexa Engelm plants over other species at a depth of 10-20 cm (average 121.6 plants). The 0-10 cm depth of soil has the greatest diversity of viable weed seeds. The 10-20 cm depth of soil provides greater accumulation of viable Callitriche deflexa Engelm seeds. The viability of weed seeds is disadvantaged in the 20-40 cm depth of soil.
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