Abstract
The ability of weeds to survive over time is highly dependent on an ecological strategy that ensures a high level of viable seed remains in the soil. Seed bank persistence occurs because of the specific characteristics of seed dormancy and longevity and the hypoxic microenvironment, which surrounds the buried seeds. These experiments investigate the role of soil texture, burial depth, and seed weight in seed bank dynamics. Seeds of twelve weed species are sown at increasing depths in various soil textures, and emergence data are used to detect the burial depth at which 50% and 95% inhibition is induced, using appropriate regressions. Clay soil is found to increase the depth-mediated inhibition, while it is reduced by sandy particles. In each soil texture, the highest level of inhibition is found for the smallest seeds. Seed weight is found to be closely related to the maximum hypocotyl elongation measured in vitro, and consequently, the seedlings are unable to reach the soil surface beyond a certain depth threshold. However, the threshold of emergence depth is always lower than the potential hypocotyl elongation. The depth-mediated inhibition of buried seeds is even more pronounced in clay soil, highlighting that the small size of clay particles constitutes a greater obstacle during pre-emergence growth. Finally, the role of soil texture and weed seed size are discussed not only in terms of evaluating the layer of “active” seed bank (soil surface thickness capable of giving rise to germination and emergence), but also in terms of developing a consistent and persistent seed bank. Finally, the role of soil texture and weed seed size are discussed, and the layer of “active” seed bank (the soil surface thickness that enables germination and emergence) is assessed with the aim of developing a consistent and persistent seed bank. Assessing seed bank performance when buried under different soil textures can help increase the reliability of the forecast models of emergence dynamics, thus ensuring more rational and sustainable weed management.
Highlights
The twelve selected weed species demonstrated a very wide range of weights for 1000 seeds (Table 1). This parameter ranged from 0.07 g for the very small seeds of Erigeron canadensis to 9.23 g for the larger Abutilon theophrasti seeds. These various seed weights were diverse in terms of the degree of achieved maximum hypocotyl elongation, as measured through the in vitro experiments
Weed seed weight and soil texture are highly influential in making the shallowest weed seed banks more or less “active.” The upper 5–6 cm of the soil layer is primarily involved in germination and emergence, and for the tested weed species, the emergence rate is absent or negligible beyond 10 cm
The maximum hypocotyl elongation of common weeds frequently exceeds 10 cm, the soil particles hinder this theoretical potential, and the extent is inversely proportional to the particle size of the soil
Summary
An important strategy for weeds is the ability to accumulate long-term viable seeds in the soil. The seed is the plant organ best equipped to tolerate high levels of agronomic disturbances. Most weed species are defined as ephemeral, short-lived plants [1], as their life cycles are mainly annual [2], implying a dynamic agroecosystem recolonization through the de-synchronized germination of buried weed seeds. Seed bank size may indicate the degree of invasiveness in a certain field—both in terms of weed density and floristic composition. Except for the potential entry of external weed seeds, due to anemochory [3], buried seeds exclusively constitute the “latent flora” that annually colonizes cultivated fields. The seed bank size usually ranges from a few thousand [4] to about
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