Water-Soluble Pyrolysis Products as Novel Urease Inhibitors Safe for Plants and Soil Fauna

Water-soluble compounds (WS) obtained from the pyrolysis of three lignocellulosic biomasses (larch, poplar, and switchgrass) were tested as potential inhibitors of the enzyme urease. Thanks to the presence of an array of phenolic compounds like catechol, methoxy/hydroxy phenols, phenolic acids, and phenolic aldehydes, all the WS samples tested at a catechol concentration of 30 μM inhibited the activity of jack bean urease (JBU) by 60%–70% and by 80% that of urease naturally present in the soil. A 10 times lower dose of WS samples (catechol concentration of 3 μM) inhibited the activity of JBU by 20%, while that of soil urease by 50%, in line with the known inhibition of N-(n-butyl) thiophosphoric triamide (NBPT). The germination rate, early growth, and development of oat were not affected by any WS sample tested at this lower dose, as well as the cress germination rate, while the development of cress roots and shoots was lower than the control presumably because of the low pH of the tested WS solutions. Earthworm survival was not significantly affected by any WS sample tested, but an effect was observed on the ability of the eggs to develop into viable newborns.