Efeitos da permanência de sementes de Soja em solo seco sobre o Vigor e a Viabilidade sob condições de restrição hídrica

Abstract

Early sowing of the Soybean (Glycine max L.) crop under low soil moisture conditions, known as "dust planting" , has become a common practice in the Cerrado regions, especially in southern Piauí, Brazil, where rainfall irregularity poses challenges to the initial crop establishment.This study aimed to investigate the effects of soybean seed permanence in dry soil, under water deficit conditions, on variables associated with vigor and viability, with the goal of understanding the physiological limits of the "dust planting" practice in southern Piauí. The experiment was conducted in a randomized block design with six periods of seed exposure to dry soil (0, 24, 48, 72, 96, and 120 hours). Variables related to vigor and viability were evaluated, including water content, electrical conductivity, germination, first count, field emergence, emergence speed index, and seedling dry mass. The results demonstrated a biphasic behavior: a 24-hour exposure promoted a significant improvement in vigor, evidenced by an increase in field emergence and emergence speed index, characterizing a physiological conditioning effect (priming). However, exposures exceeding 48 hours resulted in progressive deterioration of vigor, associated with the accumulation of damage to cell membranes and excessive consumption of reserves, particularly due to high soil temperatures, which reached up to $47^\circ\text{C}$. Despite the significant reduction in vigor, final germination remained high, indicating preservation of viability.