Last Count: An Effective Strategy for the Evaluation of Germination Indicators in Forage Species in Environmental Stress Conditions

Standardized seed tests exist to determine seed quality and for environmental monitoring. These types of trials utilize indicators that show diverse species sensitivity to environmental conditions, though the measuring moments are not always taken into consideration. The aim of this study was to evaluate the efficiency of the use of different germination indicators, and the moment they are measured, not only those frequently used, but also those generated in this study, for five forage species under different environmental stress conditions associated with the use of slurry as a fertilizer. Individual studies were carried out on Avena sativa, Zea mays, Lolium multiflorum, Vicia sativa, and Sorghum sudanense. In each study, a completely randomized factorial design (2x3x5) with three factors was applied: (a) measuring moment (72 hours and last count); (b) slurry dry matter content (0, 5, 15 % MS), and (c) electrical conductivity (CE: 0, 5, 10, 15, 20 mS/cm) of the solution. Evaluation: Germination Index (IG) and two new indicators: germinated seeds increment (ISemGUR) and root length increment (ILRUR). An ANOVA was performed for each forage species and multiple comparisons with Duncan Test (alpha = 0.05). In all forage species, IG presented significant differences between both testing moments, in at least one of the treatments and occasionally opposite effects. Therefore, measurements taken early can lead to erroneous result interpretations. Results taken at the last count would be more appropriate, especially in species with long germination periods. More trials would be necessary to measure these indicators in other moments, such as before (germination energy) or after (long term phytotoxic effects).