Evolution of Ryegrass Seed Banks Depending on Soil Tillage and Crops

Abstract

-The seed bank is characterized by the amount of seeds and other viable reproductive structures in the soil and it is changed by the input and output of seeds, being classified by its permanence in the soil as transient or permanent. The tillage and crops used decisively influence this dynamic and more disturbed areas tend to have richer seed banks. The purpose of this study was to test different soil tillage and crop systems, aiming to reduce or eliminate the ryegrass in the area. The experiment was conducted from 2010 to 2012. In the first year, the effect of chemical tillage was assessed, compared to the area without tillage. From the second year on, in the area that received chemical tillage, the second experiment was installed, where it was assessed the effect of soil tillage and crop rotation in the ryegrass seed yield. The soil tillage treatment was chisel plow and non-chisel plow. The crop rotation was: fallow/ soybean; wheat/soybean; black oat/maize. The samples of soil were taken three times a year and split in 0-5, 5-10, 10-15 and 15-20 cm. After sampling, the seeds were separated from the soil and sterilized. Afterwards, germination and tetrazolium test were conducted. In the same plots used for soil sampling, the emergence flow of ryegrass was assessed in the winter 2011 and 2012. In the first year it was observed that chemical tillage had considerably reduced the amount of ryegrass in the soil. The crop rotations used were more effective than soil tillage in reducing the seed banks in the soil. The rotation oat/maize and wheat/soybean, in only two years, practically zeroed the ryegrass seed banks in the area.Keywords: seed dormancy, chiseling, seeds viability, weeds. de culturas foram: pousio/soja, trigo/soja,[5][6][7][8][9][10][10][11][12][13][14][15] RESUMO -O banco de sementes é composto por sementes e estruturas de reprodução viáveis

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

“…The control rates were obtained from published studies for L. multiflorum, and in the absence of information, data from L. perenne were used. The latter being the Lolium species with the highest morphological similarity to L. multiflorum [31]. Management strategies and control rates were the same in both populations.…”

“…Parameters were estimated with data obtained from experiments conducted in Pato Branco (Brazil) [30] and from the literature (Table 1). In all the simulations, an initial seed bank of 2000 seeds m −2 was considered [31]. [31] Demographic and control parameters are subject to variations under field conditions, so they were considered stochastic.…”

“…In all the simulations, an initial seed bank of 2000 seeds m −2 was considered [31]. [31] Demographic and control parameters are subject to variations under field conditions, so they were considered stochastic. We modeled each parameter based on rates (except seed mortality and seed losses) by simulating its value as a random variable with a beta distribution, with a mean of µ and a standard deviation of σ and with a normal distribution for max seed by plants fecundity (f ).…”

“…The management strategies M2 to M4 rely only on the early post-emergence application of herbicide (before bloom) and late applications (after bloom) in different cohorts. The schematic representation of emergence flow, establishment and development of each cohort, and the management strategies used are shown in Figure 3 (adapted from Galvan et al, 2015) [31]. Strategy M1 does not consider any type of management and is considered as being the baseline for comparison with other management strategies.…”

“…Diagram used to describe L. multiflorum management strategies. The emergence flow and development of each cohort are described in this work, while the crops sowing is adjusted according toGalvan et al, (2015) [31].…”