Recipient Organization
TENNESSEE STATE UNIVERSITY
3500 JOHN A. MERRITT BLVD
NASHVILLE,TN 37209
Performing Department
(N/A)
Non Technical Summary
Our ability to meet food demands of a growing human population depends on healthy soils that can sustain crop production amidst changing climatic conditions. Soil health is achieved through the stabilization and efficient recycling of soil organic carbon (SOC) and nitrogen (N) within agroecosystems. This can be accomplished through the combined implementation of conservation tillage and cover crops (CCs),whichinnately addresses all four soil health management principles. Acknowledging the pivotalrole roots plays in SOC storage and stabilization, there exists asignificant opportunity to enhancesoil health by integrating CCs with improved roots traits. However, variation inshoot versus root biomass partitioning, root architecture, and chemical characteristics among CCs have been insufficiently studied, and their influence on SOC and N accumulation in both labile and stable pools remains unclear. This projectwill advance our mechanistic understanding of how CC functional types and litter traits impact soil health withinclimate-smart agricultural systems. Specific objectives include: 1) investigate how grass vs. legume CCs differ in terms of biomass partitioning, root architecture, and litter chemical recalcitrance; 2) determine interactive effects of CC functional types, litter traits, and soil mineralogy in building SOC and N in labile and stable pools under future climate warming; and 3) quantify the relative contribution of rhizodeposition and decomposing litters in building SOC and N by depth in labile and stable pools.
Animal Health Component
30%
Research Effort Categories
Basic
60%
Applied
30%
Developmental
10%
Goals / Objectives
The major goals of this project is to develop new insights into the mechanisms and drivers of soil organic carbon (SOC) storage and nitrogen (N) recycling within climate-smart agricultural systems.To accomplish this goal, we proposed these specific objectives: 1. Investigate how cover crop (CC) functional types differ in terms of shoot vs. root biomass partitioning, root architecture, and litter chemical recalcitrance; 2.Determine the interactive effects of CC functional types, shoot vs. root litter traits, and soil mineralogy on the storage and stability of litter-derived SOC and N into labile and stable pools under future climate warming; and 3.Quantify the relative contribution of rhizodeposition, as well as decomposing shoot vs. root litters of functionally distinct CC types in building SOC and N by depth into labile and stable soil pools in agroecosystems.
Project Methods
Objective 1. Investigate how CC functional types differ in terms of shoot vs. root biomass partitioning, root architecture, and chemical recalcitrance.An outdoor mesocosm experiment will be conducted at the TSU Agricultural Research and Education Center (AREC) farm. Four CCs differing in their functional types (i.e., two grass CCs: cereal rye and winter wheat; two legume CCs: crimson clover and hairy vetch) will be planted in the fall of 2024 (early October) and left to grow until Spring 2025 (early May) under outdoor conditions. Four mesocosms of each CCs will be destructively harvested three times (late fall, early spring, and late spring) to test how winter and spring growing conditions influence shoot and root growth patterns of these four functionally distinct CCs. In total, 48 mesocosms will be prepared (i.e., 4 CCs × 3 destructive harvests × 4 reps = 48).At each destructive harvest, CC shoots will be clipped near the surface and oven-dried at 60 °C for 7-10 d to determine the total shoot dry biomass. Each mesocosm containing the roots and growth medium will then be transferred to a table where it will be gently washed to avoid root breakage. Once washed, the root systems will be imaged using a high-throughput root phenotyping platform that captures and processes root images. The root architectural traits of interest include rooting depth, average root diameter, total root length, total root surface area, and total root volume. Following root imaging, roots are oven-dried at 60 °C for 7-10 d to determine total root dry biomass and root:shoot ratio. Oven-dried shoot and root materials will be finely ground and analyzed for C and N concentrationsas well as litter chemical recalcitrance (i.e., carbohydrate, cellulose, hemi-cellulose, and lignin concentrations).Objective 2. Determine the interactive effects of CC functional types, shoot vs. root litter traits, and soil mineralogy on the storage and stability of litter-derived SOC and N into labile and stable pools under future climate warming. We will conduct a laboratory incubation experiment to determine how shoot vs. root litters of two functionally distinct CCs (i.e., cereal rye and crimson clover) promote SOC storage and N cycling into particulate vs. mineral-associated pools of two contrasting soil types (Maryland and Tennessee soils). Both these soils will bewetted to field capacity with deionized water and pre-incubated for 3 weeks. After the pre-incubation, soils (50 g equivalent dry weight) and CC litter materials (2.5 g equivalent dry weight) will be weighed in 100-mL plastic beakers (5.0 cm diameter), and mixed well. Microcosms of unamended soil will be included as controls. Triplicate microcosms for each CC litter by soil type combination will be incubated at two different temperatures: the current average spring temperature of 8.7 °C and under a future climate warming scenario at 14.7 °C. Therefore, a total of 108 jars will undergo incubation based on (2 CC types × 2 harvest dates × 2 litters + 1 unamended control) × 2 soils × 2 temperature × 3 replicates. The jars will be weighedweekly to determine weight loss and adjust for any water that has been lost.We will fractionate the bulk soil at the start and end of incubation into particulate and mineral-associated SOC pools.The C and N concentrations, as well as the δ13C/δ15N of the litter (initial) and soil fractions (initial and final) will be measured using an Elemental Analyzer - Isotope Ratio Mass Spectrometry (EA-IRMS). Throughout the incubation, the total CO2 concentration in the jars and δ13C of CO2 will be measured by connecting the jars to a Picarro G2131-i analyzer (Picarro Inc., Santa Clara, CA, USA).Furthermore, we will quantify how different CC functional types and litter traits form organo-mineral complexes with pure soil mineral phases. For this, DOC will be extracted from shoot and root litters of two functionally distinct CCs (cereal rye and crimson clover) and the DOC sorption capacitwill be determined on three soil minerals including ferrihydrite (iron oxide), birnessite (manganese oxide), montmorillonite (clay), and quartz sand as a control. To determine the in-field stability of these organo-mineral complexes, mesh bags containing the organo-mineral complexes ill be buried 15 cm below the soil surface and left to incubate in fields for four months from June to September. The bags will be retrieveded and analyzed using EA-IRMS for C and N concentrations as well as δ13C/δ15N.Objective 3. Quantify the relative contribution of rhizodeposition, as well as decomposing shoot vs. root litters of functionally distinct CC types in building SOC and N by depth into labile and stable soil pools in fields. Field experiment will be established at the TSU AREC farm in a randomized complete block design with CCs as the main treatment: cereal rye, crimson clover, and no CC control. Each experimental unit will be 5 × 5 m2 and replicated four times. Cover crops will be seeded in the fall (late September) using a no-till grain drill.No CC control plots will be maintained weed-free using glyphosate and 2,4-D. In early May, before termination, CC shoots will be collected from 2 × 2 m2 from each plot and transferred to the bare fallow control plots to create a 'shoot only', 'root only', and 'both shoots + roots' micro-plots. Thus, we will have a total of seven treatments during the CC decomposition phase of the study. Four soil cores (10 cm diameter) will be collected from 0-30 cm depths in each plot and partitioned into three depths (0-10 cm, 10-20 cm, and 20-30 cm). To determine how CC functional types affect the relative contribution of rhizodeposition into labile and stable SOC and N pools, soil cores will be collected twice during the CC growth phase: at or prior to CC planting and termination. Additional soil cores will be collected from all seven microplots three times during the CC decomposition phase at 1, 6, and 15 months after CC termination. Bulk soils from each depth will be fractionated into particulate and mineral-associated pools, and then oven-dried, weighed, finely ground, and analyzed for C and N concentrations, as well as the δ13C/δ15N of the soil fractions using EA-IRMS. We will also determine C and N concentrations, δ13C/δ15N, as well as chemical recalcitrance in the shoot and root litters from each CCs.