Thursday, 24 May 2012

Secret soil cracks linger, despite surface sealing

Here's an interesting story which is highly relevant to parts of the UK at the moment, where a prolonged drought has been followed by intense, heavy rainfall in the past few weeks.   Are those heavy soils really suddenly waterlogged, or is it just surface water sitting on top of a compacted soil layer which is hiding drought-induced cracks further down?

BrightSurf.com reports that deep cracks in soil can remain open underground even after they have visibly sealed on the surface, a new study has found. The results could have important implications for agricultural management around the timing and intensity of water and pesticide applications.

Cracks in the soil, which open up when the soil is particularly dry, provide "preferential pathways" allowing water to flow much faster than it would through non-cracked soil, rapidly transporting nutrients and pesticides beyond the crops' root-zone. If the plants can't access the water it has effectively been wasted.

Studying this preferential flow, the researchers have found that surface appearances can be deceiving. "We showed that soil cracks that developed in dry periods remain open as preferential flow paths, even after the cracks are visually closed," said lead author Dr Anna-Katrin Greve, a postdoctoral fellow with UNSW's Connected Waters Initiative. She found, however, that lower water application / irrigation intensity will give soil cracks time to close and more frequent irrigations could prevent the soil cracks from reforming.

Read more here.