A Proposal for Evaluation of Seedling Emergence and Growth under Mechanical Impedance

Compaction can affect the emergence and growth of seedlings and, consequently, harm the development of the culture. However, there are no standardized methodologies that allow evaluating the characteristics of seedlings grown in high mechanical impedance. Thus, the objective of this research was to develop an efficient, standardized, and reproducible methodology to assess seedling emergence and growth in response to increased mechanical impedance, using soybean as a model crop. The proposal consists of a PVC (polyvinyl chloride) column on a tray, both filled with sand of standardized granulometry. A perforated metallic disk is placed on the surface of the column, which receives loads to simulate different levels of mechanical impedance (0.15; 0.60 and 0.87 MPa). Seeds of four soybean cultivars were planted inside the holes of the discs and cultivated for 7 days. The high penetration resistance of the roots did not affect the final percentage of emergence of soybean seedlings. However, speed and uniformity of emergence; volume, length, diameter, surface area of roots; and biomass production of roots and shoots respond to treatments and provide the screening of soybean cultivars in different groups of mechanical impedance response. The methodology allows an efficient, standardized and reproducible estimation of the percentage and speed of emergence, as well as the growth characters of seedlings under increasing mechanical impedance.