Temporal Persistence of the Biological Effects of a Seed-Applied Biostimulant on Wheat (Triticum aestivum) Germination and Early Growth Under Extended Pre-Germination Soil Drought.

Delayed post-sowing watering may leave treated wheat (Triticum aestivum) seeds in dry soil for several weeks before germination begins, raising the question of how long the effects of seed-applied biostimulants remain biologically active under these conditions. This study evaluated the persistence of the biological effects of a seed-applied biostimulant, applied alone (BS) or combined with a triticonazole-based fungicide (TBS), after delayed watering of wheat seeds. Seeds were watered immediately after sowing or after 2, 3, 4, or 5 weeks and evaluated in Petri dishes and growth pots. Compared with the untreated control, BS and TBS reduced mean germination time by up to 9.4 h and 8.7 h, respectively (p < 0.05), while also promoting greater seminal root development after prolonged exposure to dry conditions. In the pot experiment, treatments including the biostimulant maintained greater root dry weight at both BBCH 11 and BBCH 12, indicating that a measurable stimulatory response was still observed beyond germination and early seedling establishment. The strongest responses were observed when watering was delayed by 2-3 weeks, remained evident after 4 weeks, and declined after 5 weeks of dry sowing conditions. Under the conditions of this experiment, the results demonstrate that, although the biostimulant supports early root system development after moisture restoration, the magnitude of the treatment response is conditioned by the duration of the pre-germination waiting period.