Allelopathic Effects Of Dried and Composted Pistia Stratiotes and Lyngbya Wollei On Rice and Sorghum Growth.

Invasive aquatic plant species interfere with farm canals’ function and cause negative environmental impacts in the Everglades Agricultural Area in south Florida. Pistia stratiotes (WL) [water lettuce] and Lyngbya wollei (FC) [filamentous cyanobacteria] are two common plant species of floating aquatic vegetation (FAV) prevalent in the area and several management approaches such as harvesting and field incorporation have been implemented for their control. Our goal was to investigate the use of these species as soil amendments. Past studies have shown allelochemicals and inhibitory effects of FAV on plant growth under controlled laboratory settings; however, environmental conditions may influence their allelopathic activity when applied to the soil. In this study, a split-pot experiment was conducted to compare and evaluate the effects of dried and composted WL and FC applied on rice and sorghum grown on muck and sandy soils. Evaluation of rice root dry weight (RDW) showed that dried FC applied in sandy soils resulted in significantly less RDW compared to dried WL and composted WL and FC applied in muck soils, which may indicate a negative allelopathic effect of dried FC when incorporated in sandy soils for rice growth. In contrast, no negative effect was caused by the amendments on sorghum growth; moreover, greater RDW was observed when dried WL was applied in sandy soils compared to muck soils, suggesting the opportunity to use dried WL amendment in coarse-textured soils to grow sorghum. The allelopathic effects of dried and composted FAV varied by soil type, environmental conditions, and crops.