Longevity and persistence of arrowleaf sida seeds in soil and emergence modeling using thermal and hydrothermal time models

Arrowleaf sida (Sida rhombifolia L.) is a weed that has a fibrous stem, aggressive root system and waxy leaves that can hinder herbicide absorption. Based on knowledge of the environmental requirements for germination of this species, it is possible to predict emergence to assist in integrated management. The aim of this investigation was to characterize the air temperature and soil water potential requirements for arrowleaf sida germination, to model the emergence in the field using thermal and hydrothermal time models and to evaluate the longevity of the arrowleaf sida seed bank. Laboratory experiments were conducted to determine the temperature and water potential for seed germination by testing eight temperatures (10, 15, 20, 25, 30, 35, 40, and 45 °C) and 10 water potentials (0, −0.05, −0.1, −0.2, −0.4, −0.6, −0.9, −1.2, −1.5, and −2.0 MPa). Field experiments were conducted between 2014 and 2018 to model the emergence using three sampling times (starting on 10/20, 11/10, and 12/01), during which soybean seeds were sown. To evaluate the longevity and persistence of the seed bank, a factorial experiment was conducted, in which the first factor included three burial depths (0, 3, and 6 cm) and the second factor included five collection times (0, 1, 4, 10, and 16 months) after seed burial. The base, optimal and maximum temperatures for arrowleaf sida germination were 10.0, 24.8, and 42.5 °C, respectively, and the base water potential was −1.20 MPa. It is possible to predict the emergence of arrowleaf sida in the field by hydrothermal and thermal time models under different environmental conditions. In addition, this species has a persistent seed bank, with 30% of seeds being viable after 16 months of burial.