The research under me and associated with me are contributing to address major challenges facing soil scientists this century:
stagnation/slow accrual of soil organic matter in agricultural soil, eutrophication of water resources, and mitigation of global warming impact on agriculture, particularly crop yield.
Biosolids and Soil Ecosystems Research
The continuous rise of carbon dioxide in atmosphere has become a globe concern for climate change. Soil C sequestration means the carbon dioxide in atmosphere is stored in soil through the synthesis of photosynthesized plant residue-C into soil organic matter (SOM) in ecosystems. The mean residue time (MRT) of C in SOM is 50 years, whereas the MRT of plant residue-C in temperate is 2 years, that the soil C sequestration buys us time for the mitigation of CO2 concentration in atmosphere.
In US Midwest, 3-4 tons C/ha/yr in corn stalk are left in the field after the grain harvest. However, only about 0.4 tons of these C can be synthesized into SOM, whereas about 90% of crop residue-C returns to atmosphere in 1-2 years. Meanwhile, the microbial decomposition of existing (old) SOM at a rate of 0.08 to 1.5% releases about 0.4-0.45 tons/ha/yr of C to atmosphere. Generally, there is no net soil C sequestration under continuous cultivation, the C-neutral is the best an Ag soil can maintain, which is due to the “cultivation” effect. Straightly speaking, for growing crop and sequestering C by soil, without a new intervention, we can only choose one, not two. Of course, we need the soil to produce corn, and this means we have to find a new way to increase the transformation of crop residue-C to SOM in order to achieve C sequestration in soil. Thus, the soil C sequestration sounds a good idea to mitigate the CO2 rise, but it is hard to put it into practice.
Our work at the Fulton county with a series of projects initiated in 1972 has showed the microbial adaption to environmental stress in agricultural soils is the chief reason for the difficulty of soil to achieve soil C sink (sequestration > emission). An important finding is our discovery that municipal biosolids double the amount of crop-C sequestered in SOM, and furthermore we identified the mechanism – which was that biosolids decreased microbial nutrient stress. The biosolids are organic (20-30% org. carbon, 1.5-3% org. N) based materials derived from sewage sludge as byproduct of treating domestic and industrial wastewater and processed to meet USEPA 40 CFR part 503 regulations for heavy metal concentrations, pathogen reductions, and product stability. This work has been put in on-going experiments in western Illinois to develop a biosolids-soil management system for increasing yearly C sequestration, increasing corn yield, and reducing synthetic fertilizer to help mitigate climate change impact on agriculture; to regenerate brownfield soil health (soil respiration, microbial biomass, and nitrogen mineralization potential) and ecosystem function (plant biomass production, C sequestration, below-ground energy transfer, and plant diversity), degradation of soil organic contaminants, and re-establishment of native plants.
On-going research:
Long-term impact of biosolids amendment on crop yields and soil health - Seeking a more effective way to jumpstart SOM by the use of biosolids for greater crop yield stability and reduced chemical fertilizer needs under climate change, particularly achieving a new level of soil health for long-term sustainability.
Soil carbon sequestration for agricultural soil CO2 emission reduction - Conducting research on soil carbon sequestration to address a key research question on how to transcend agricultural soil low SOC equilibrium via microbial stress alleviation by biosolids.
Reconstruction of native ecology/plants by biosolids - my group (Dr. Theresa Johnston) is establishing research in Chicago metropolitan areas on the biosolids for brownfield restoration focusing on the restoration of degraded urban soils to native ecosystems using biosolids.
Soil and Nutrient Management in Agroecosystems (Illinois) Research
for Reducing Nutrient Loss from Agricultural Fields to Mississippi River
Under U.S. EPA Gulf Hypoxia Action Plan, the 12 states in the Mississippi River Basin are required to reduce the loss of nutrients (nitrogen and phosphorous) to the Gulf by 45%. Illinois published the “Illinois Nutrient Loss Reduction Strategy” in 2015 (State of Illinois, 2015). Under the Strategy, besides the removal of nutrients in wastewater treatment, MWRD initiated an agricultural nutrient loss reduction program at its Fulton County research facility since agriculture contributed to 80% of N and 48% of P export to Mississippi River.
Agricultural best management practices (BMPs), such as cover crop, no-tillage, grass or riparian buffers, runoff irrigation, drainage water management, bioreactor, and saturated buffer, can reduce nutrient loss from agricultural fields. However, many of these BMPs need to be further developed for the Illinois climate condition and tested on a large scale to increase the rate of adoption by farmers. Under the Nutrient Loss Reduction Research and Demonstration Program at the Fulton County station, my group is collaborating with University of Illinois at Urbana-Champaign’s (UIUC) Crop Science Department, Department of Agricultural and Biological Engineering, and Illinois Sustainable Technology Center, Illinois Central College, Ecosystem Exchange, Iowa, Illinois Farm Bureau, and Fulton County Farm Bureau in further developing those BMPs and demonstrating their effectiveness in reducing nutrient loss from agricultural fields on a large scale.
The on-going research:
Interseeded cover cropping - In Illinois, the winter cover crop planted at or shortly before the main crop harvest might miss the high soil N load in fall due to the short duration of days to frost after the primary crop harvest. At the Fulton County site, we are developing a cover cropping system that can have a greater N demand during the offseason to effectively capture the N unused by corn in a field scale. We use an interseeder to sow the cover crop (rye grass or cereal rye) at 4-5 weeks after corn planting. The cover crop grows slowly and even remains dormant until corn harvest. After the corn harvest, the cover crop grows rapidly to utilize residual N and develop groundcover to reduce the runoff. The measurements include cover crop biomass, rooting system, N and P uptake, plant residue decomposition and nutrient uptake by the main crop, soil solution N and P, root mycorrhizal fungi association with phosphorus uptake, and soil carbon sequestration.
Multi-functional riparian grass buffer - A riparian buffer is a vegetative zone at the edge of fields that intercepts runoff water and sediments. The effective riparian zone also contributes to N removal through supporting denitrifying bacteria in the root zone. In collaboration with Dr. D.K. Lee at UIUC's Crop Science Department, we are testing the effectiveness of forage mixtures as a riparian buffer for efficient reduction of N and P discharge to a nearby creek and the potential for biomass harvest as animal feeds. The riparian zone strip (2,000 feet x 50 feet) along Big Creek at the Fulton County site was established with forage crop mixture and a control. The measurements include forage biomass and N and P uptake, leachate N and P concentration, soil N-cycling bacteria community, greenhouse gases, and N and C sequestration.
Denitrifying bioreactor - The water from field drainage tiles can be routed to flow through a buried trench filled with woodchips. A group of bacteria (denitrifiers) uses the carbon in the woodchips as their food and converts the nitrate into nitrogen gas (N2). The bioreactor can also remove the P in drainage when a P-sorption medium is included. As an edge of field practice, the impact of the woodchip bioreactor on farm operations and profits will be negligible. My group (Dr. Olawale Oladeji) and collaborator (Dr. Richard Cooke) have established the bioreactors at an 80-acre field, and inlet and outlet flow is monitored by transducers, and water is periodically sampled for determination of N and P concentrations over seasons and years.
Designer biochar P removal - We are collaborating with Dr. Wei Zheng at UIUC's Illinois Sustainable Technology Center and Dr. Richard Cooke at UIUC's Department of Agricultural and Biological Engineering for the designer biochar P removal project, funded by EPA. The project started in 2020 is to develop and scale up an innovative biochar-sorption-channel (B2) treatment system to effectively capture nutrients from subsurface drainage water and recycle nutrient-captured biochars as a slow-release fertilizer.
Sub-irrigation - The runoff and/or drainage water collected in a retention basin from agricultural fields can be pumped back onto production areas for irrigation. The nutrients in agricultural runoff/drainage water can partially satisfy the nutrient needs of corn. Soil moisture due to irrigation can help corn develop roots, leading to the better utilization of fertilizer by corn. The increase in cost for pumping the water could be offset by the decrease in fertilizer needs due to the recycling of nutrients in the runoff water and increase in crop yield. Dr. Oladeji is managing a runoff irrigation project for testing the possibility for up to a 50% reduction in corn fertilizer need by using the runoff irrigation. The measurements include crop yield and N and P concentration, soil nutrient status, and economic analysis. In the Illinois Nutrient Research and Education Council (NREC) funded-joint sub-irrigation project (University of Illinois at Urbana-Champaign, MWRD and Illinois/Fulton County Farm Bureau), water seeps out of the perforated tile, and is delivered to the crop root zone upwards from below the soil surface through capillary action to reuse nutrients from agricultural fields and to optimize crop yield at reduced fertilizer use.
Quantification of BMP Effectiveness at Field-Based Watersheds - Since many of the fields at the MWRD’s Fulton County site are bermed, runoff from a field can be directed to one outlet, similar to a watershed, for monitoring. The United States Environmental Protection Agency’s paired watershed research approach is used in the field-based watershed monitoring. The first three years are the calibration period to characterize the watersheds and establish the baseline data. Since during the calibration period, the paired fields are managed in the same way, the existing difference between them in the amount of nutrient export through runoff to surface water can be obtained. A set of BMPs are installed in one field of each pair after calibration, and the monitoring will continue for another five to ten years to obtain the difference between the paired fields in amount of nutrient export through runoff to surface water after the installation of BMPs. Any change in the difference between the paired fields in the amount of nutrient export through runoff to surface water will be attributed to the BMPs’ effect. We have three pairs of fields, representing three levels of soil N and P, equipped with flow meters, automatic samplers, and rain gauges. Runoff generated after rains is continuously quantified and sampled for the analysis of suspended solids, nitrate, and total P. The nitrate and water soluble P loss through subsurface leaching is also being assessed using a Rhizon soil solution sampling system. The data are being used for modelling to predict BMPs’ effects on water quality at regional scales, and in particular, to generate outputs on how much area BMPs should cover in order to attain predetermined water quality improvements in Illinois.
Further information on Fulton County Nutrient Loss Reduction studies : https://mwrd.org/fulton-county-nutrient-loss-reduction-strategies
Agri-News: Rural-urban collaboration yields alternative solutions to improve state water quality
https://www.agrinews-pubs.com/news/science/2021/01/03/rural-urban-collaboration-yields-alternative-solutions-to-improve-state-water-quality/