Agriculture currently encompasses ~ 1/3 of the earth’s land surface, and replaced almost the entirety of the grassland ecosystems which originally occupied these semi-arid regions (UNEP 2014). However the serious erosion and degradation of lands globally due to long-term agricultural practices of clearing, tilling, harvesting, and overgrazing is a major impediment to increasing food production to meet the needs of our rapidly growing human population (WRI 2013). Globally, soil erosion is estimated to impact 1.3 billion ha of land area (Lal 2003). In the U.S., the historically high productivity of the Great Plains depended on deep organic soils, but their conversion into corn, wheat and rangelands has significantly impacted these systems, with an estimated 1.7 billion tons of soil eroded annually (NRI-USDA 2007). This chronic removal of soil organic matter impacts fertility and crop yields. It also reduces the soil’s ability to capture and store rainfall in semi-arid regions which receive less than 600 mm of precipitation annually (MEA 2005). Thinner soils have less resiliency as regions experience more and hotter droughts due to climate change (IPCC 2014). Irrigation demands, which already account for ~70% of all human water consumption, will increase to compensate for the poorer soils. It is absolutely critical that we focus on restoration of agricultural grassland systems to achieve food and water security in coming decades.
Over the past 5 yrs, an international team of researchers, lead by Cornell faculty, has been working on the development of techniques and “recipes” for jumpstarting soil health and the restoration of degraded and desertified agricultural grasslands. The cornerstone of our approach is the use of coarse woody organic matter, incorporated both subsurface and aboveground, to capture and store infrequent rainfall, along with fertilizer for nutrients, a microbial innoculum, and biochar where needed and feasible. Through a combination of laboratory-based microcosms and scaled-up field plot experiments, we have successfully demonstrated that these techniques increase rainfall capture and maintain higher soil moisture contents for several weeks post-rainfall (SSSA –Special Session, 2016). Furthermore, addition of fertilizer into the recipe leads to increased wheat and alfalfa production, with current positive applications in saline soils as well. Selection of biochar (Lehmann 2015) and slow-decomposing wood species show particular promise as a mechanism for significant carbon sequestration. We have also documented that night-time condensation within a healthy grass canopy can replace 23.3% of water lost daily in transpiration and reduce evaporation losses, thus providing a significant, but previously overlooked, source of water which augments scarce rainfall. Re-establishment of grass communities will be critical for self-sustaining, non-irrigated systems, so we are developing a portfolio of options that includes switchgrass for biofuels, limited livestock grazing, and perennial grains. Thus far, we have demonstrated the success of this approach, first in the severely degraded soils of the Yellow River Valley, Ningxia, China and more recently at USDA’s Northern Great Plains Research Lab in Mandan, North Dakota.
Our work has received Flagship status for the USDA-China Ministry of Science and Technology Collaborative Program (2011-2017), was highlighted in 2015 by US Ambassador M. Baucus as one of the three most collaborative programs between the US and China, and in the keynote address at the C20 Conference (G20 subcommittee) on 5 July 2016 in China.
Wetland Soil Restoration
Ballantine, K. and R.L. Schneider. 2009. Fifty-five years of soil development in restored freshwater depressional wetlands. Ecological Applications 19 (6): 1467-1480. DOI: 10.1890/07-0588.1
Ballantine, K., R.L. Schneider, P. Groffman, and J. Lehmann. 2011. Soil properties and vegetative development in four restored freshwater depressional wetlands. Soil Science Society of America Journal 76(4): 1482-1495. doi:10.2136/sssaj2011.0362
Ballantine, K.A., P.M. Groffman, J. Lehmann, and R.L. Schneider. 2014. Stimulating nitrate removal processes of restored wetlands. Environmental Science and Technology 48(13): 7365-7373. DOI: 10.1021/es500799v
Ballantine, K.A., J. Lehmann, R.L Schneider, and P.M. Groffman. 2015. Trade-offs between soil-based functions in wetlands restored with soil amendments of differing lability. Ecological Applications 25(1): 215-225. DOI: 10.1890/13-1409.1
this page is under construction – last update 5 October 2016