Successful Applicaton of Woody Organic Matter Amendments to Increase Rain Capture and Soil Moisture Content in Degraded Ag/Grassland Soils.

Restoration of degraded ag grassland soils is urgently needed globally. A key issue is the chronic erosion of formerly deep soil organic layers which allowed grasslands to capture and store rain between infrequent rain events. For the past five years, an international team of researchers has been investigating the use of woody organic matter amendments to improve the health of soils in Ningxia, China which currently consist of 98% sand with less than 1% organic matter content. A field study, based on microcosm experiments, was set up in 2012, with five replicated, 9 m² plots each of controls and three treatments: soils with Populus wood chips incorporated into the top 20cm of soil (GBI), soils with GBI plus an over-arching branch lattice shelter (GBI + B), and soils with only a woody surface mulch (GBM). Gravimetric soil moisture content was monitored ~ weekly in in 2012 and again in 2015. Significantly greater amounts of water were captured during rain events in the woody amendment treatments as compared to the controls, with soil moisture contents maintained at higher levels for several weeks post rainfall. This pattern was observed in 2012, and was still present three years later. GBI + B exhibited the highest soil water contents, had the lowest soil temperatures, and had moss and mushrooms growing under the branch shelters in July 2013. Comparable patterns in volumetric water content were observed when the experiment was conducted in less degraded soils at the USDA’s Northern Great Plains Research Lab in North Dakota in 2015. We conclude that coarse woody amendments can play a key role in jumpstarting restoration of seriously degraded ag/grassland soils.