Experimental evaluation of organic substrates for germination testing of soybean seed

High germination of seeds and seedling establishment are critical for soybean production since it determines crop density and eventually affects the yield. Accurate evaluation of the germination potential of sowing material is valuable, as well as initial quality assessment of newly harvested seed. ISTA Rules prescribe alternative methods for soybean seed germination: sand, between paper, top of paper covered with sand and since 2020 organic growing media. In the Seed Testing Laboratory at the Maize Research Institute soybean germination is conducted in the sand at 20<=>30°C. The objective of this study was to evaluate several available organic growing media and compare results obtained with the standard laboratory method. Five soybean seed lots of different quality were tested in four germination growing media (3 organic and sand), at two temperature regimes (25 °C and 20<=>30°C). Statistical analyses showed that all types of organic growing media were of the same quality. Slightly higher germination in organic growing media was obtained in the experiment at 20<=>30°C compared to sand, but those differences were not statistically significant. When testing was done in germinator with 25°C positive effects of organic growing media were identified and this impact was significant, especially for low-quality seed lots. The experimental outcome was to continue with routine practice and use organic growing media for retesting of seed lots with lower germination as an alternative substrate.