Lolium multiflorum seeds in the soil: I. Soil seed bank dynamics in a no til system

Abstract

RESUMO -O estudo objetivou a caracterização da dinâmica de populações de sementes de azevem anual em manejo de revegetação, em um sistema de plantio direto em rotação com soja, em diferentes seqüências. A soja foi cultivada por dois anos e cultivada novamente depois de dois anos de pousio. As quatro seqüências representaram diferentes períodos de manejo, dois deles com soja (6 e 8 anos) e os outros dois restantes (3 e 9 anos). Amostras de solos foram tomadas a cada mês, durante um ano, em duas profundidades (0-5 e 5-10 cm). A dinâmica de vegetação foi também avaliada (numero de plantas, inflorescências e plântulas). A dinâmica do banco de sementes do solo (SSB) mostrou padrão estrutural no tempo, com um período de armazenamento no verão, um período de exaustão durante o outono e um período de transição no inverno e primavera. O estabelecimento de pastagem por revegetação natural 'e` totalmente dependente do banco de sementes do solo. A influ^encia das praticas de manejo no SSB e mais importante do que o numero de anos que estas praticas tem sido implementadas. Locais onde a soja foi cultivada mostraram maior SSB. A maior parte das sementes teve sua dormência quebrada e germinaram no final do período de verão e começo do outono, mostrando um típico SSB transitório, mas com pequena proporção de sementes persistentes.Palavras chaves: azevem annual, pastagem annual, soja, pastagens, plantio direto. Lolium multiflorum SEEDS IN THE SOIL: I. SOIL SEED BANK DYNAMICS IN A NO TILSYSTEM 1 ABSTRACT -The objective of the study was to characterize annual ryegrass seed population dynamics, managed for natural re-sowing, in no til systems in rotation with soybean, in different chronosequences An area was cultivated for two years with soybean, left as fallow land for the next two years and then cultivated again with soybean for the next two years. The four chronosequences represented different management periods, two with soybean (6 and 8 years old) and the other two resting (3 and 9 years old). Soil samples were taken every month during one year and divided into two depths (0-5 and 5-10 cm). Vegetation dynamics were also evaluated (number of plants, inflorescences and seedlings). Soil seed bank (SSB) dynamics showed structural patterns in time, with a "storage period" in summer, an "exhausting period" during autumn and a "transition period" in winter and spring. Pasture establishment by natural re-sowing was totally dependent on the annual recruitment of seeds from the soil. The influence of the management practices on the SSB was more important than the number of years that these practices had been implemented. Places where soybean was sown showed the largest SSBs. Most of the seeds overcame dormancy and germinated at the end of the summer and beginning of the autumn, showing a typically transitory SSB, but with a small proportion of persistent seeds.

Modeling the Population Dynamics and Management of Italian Ryegrass under Two Climatic Scenarios in Brazil

“…The seed bank observed in the baseline Scenario 1 (M1) was 19,121 ± 371 seeds m −2 (susceptible population) and 20,463 ± 363 seeds m −2 (resistant population). These results are in agreement with the seed bank observed in farming areas for L. multiflorum [18]. These population levels are high enough to cause severe yield losses if the weeds are not controlled [19].…”

Prediction of Italian ryegrass (Lolium multiflorum L.) emergence using soil thermal time

“…Studies that evaluate the emergence of Italian ryegrass show that the process occurs mainly in the first half of the autumn (Maia, Maia, Bekker, Berton, & Caetano, 2008). It is believed that it occurs in this period due to the seeds primary dormancy being terminated in the after-ripening period, when they are exposed to high temperatures during the summer (Ichihara, Yamashita, Sawada, Kida, & Asai, 2009).…”

Demographics of glyphosate-resistant and susceptible Italian ryegrass populations from Paraná

“…A field experiment was conducted in RBD with four replicates in a factorial arrangement. The first factor was two Italian ryegrass populations (susceptible and resistant); the second factor was three cohorts (March, April, and June), simulating an Italian ryegrass natural emergence (Maia et al, 2008). For seedling development, in a greenhouse, seeds were sown in 294 cell plastic trays in three timings: 14/03/2018 (cohort 1), 14/04/2018 (cohort 2), and 19/05/2018 (cohort 3).…”