Progress report for GS24-297
Project Information
South Texas soils are predominantly low in organic matter contentand often face serious nutrient loss challenges during crop production. Record low rainfall in the last few years in South Texas has also become an imperative area of concern. A long-term research field at Texas A&M AgriLife has been practicing cotton-sorghum crop rotations over the last 30 years. However, an integration of cover crop mixtures (annual ryegrass, Austrian winter pea, tillage radish, hairy vetch, buckwheat, and oat) with two different tillage (no till vs conventional till) methods was initiated four years ago to experience the ecosystem services those cover crops has to offer, specifically in regard to adding organic matter in the soil. However, a soil carbon balance (SCB) considering both C inputs and outputs in that field has not yet been developed.
This study will: a) evaluate the efficacy of cover crop mixtures to add soil carbon and develop SCB b) account for meteorological parameters and soil physicochemical properties to better understand SCB and c) provide experimental and experiential learning opportunity to the graduate student about sustainable farming. We will use a LI-7810/7820 CH4/CO2/N2O/H2O Trace Gas Analyzer to measure greenhouse gas emissions for two crop seasons. One-meter-deep cores samples will be collected to measure carbon content in soils at different depths. Total carbon contributed and total carbon released from different treatments will be used to calculate SCB.
The outcomes of this experiment will be disseminated through presentations at conferences, peer-reviewed article publications, webinars, farmers field-day demonstrations, and classroom presentations.
This project will follow a system-based research approach (as outlined in the SARE website) where agricultural sustainability will be introduced and analyzed in a conventional farming system (long-term cotton and sorghum rotations). This project will address the key research question: “Are cover crop mixtures capable of providing ecosystem services in a semi-arid row crop production system?” Specific objectives are:
Objective # 1. To develop a soil carbon budget under six cover crop mixtures (annual ryegrass, Austrian winter pea, tillage radish, hairy vetch, buckwheat, and oat) and tillage practices (no till and conventional tillage) in a long-term row crop (cotton and sorghum) production farming. One-meter soil cores will be collected and divided into five segments (depth of 0-5 cm, 5-10 cm, 10-30 cm, 30-60 cm, and 60-90 cm) for soil C analysis and eventually to feed into a DAYCENT model in the future. Other soil cores will be collected to measure the field bulk density of soil at those five depths. Seed mix of these cover crops were selected based on the grower’s recommendations and the performance of those cover crops in the semi-arid climate. Specifically, we selected a mixture of legumes (hairy vetch and Austrian winter pea), grasses (annual ryegrass, oat, and buckwheat) and broad leaf (tillage radish or Daikon radish) cover crops for efficient use of the soil moisture and nutrients at different soil depths. We are anticipating a possibility to continuing this study even after finishing this two-year project.
Hypothesis 1A: Cover crop mixtures will have positive impacts on soil carbon balance (net C accumulation) in the field compared to the plots without cover crops.
Hypothesis 1B: No tillage (under CC treatments) will retain more soil carbon than conventional tillage (under CC treatments)
Objective # 2: To consider the effect of meteorological parameters (temperature, rainfall, relative humidity, and wind speed) and soil physicochemical properties (gravimetric water content, water filled pore space, organic matter content, bulk density, soil pH, and cation exchange capacity) on soil C balance. Meteorological parameters can largely influence carbon emission and accumulation in soil. PI’s previous project have shown a significant effect of meteorological parameters on trace gas emissions from soil in row crop production system (Dattamudi, 2015).
Hypothesis 2: Meteorological parameters and soil properties will have a significant effect on soil respiration and cover crop residue decomposition (to add organic matter in the soil) which will subsequently influence the soil C balance.
Objective # 3: To disseminate information and knowledge among the growers, other stakeholders, and fellow classmates through grower meetings, extension activities, conference presentations, classroom demonstrations, and peer-reviewed publications. Additionally, social media platforms such as Facebook, Instagram, College website, College Newsletter, and LinkedIn will be used to disseminate the research outcomes of this study.
Hypothesis 3: Knowledge dissemination will provide more information to the growers and other agricultural stakeholders about the influence of cover crop treatments and conservational tillage practices (no-till) on soil carbon dynamics.
Research
- Foster_Support_E Zamora 2024 Figure 1. Pictures of the Field plots and cover crops
- Site location and experimental details
This experiment will be done at Texas A&M AgriLife Research and Extension center located in Corpus Christi, Texas. Cotton (Gossypium hirsutum L. Var: BASF ST 5471 GLTP) and sorghum (Sorghum bicolor L. Var: DKS 54-07) are the main row crops grown in this research station. The graduate student at TAMUK will work at this research field with other team members at the station. We attached support letter from Dr. Foster (a Professor of Agronomy at this station) with this proposal.
The experiment plot (Figure 1) will consist of six treatments in a randomized complete block design (RCBD) with four replications for each treatment. Two replications each for cotton and sorghum field will be used.
Two tillage practices are a) No tillage or zero tillage (NT)
b) Conventional tillage (CT) system (disking, chiseling, post-planting land preparation)
Three cover crop mixture treatments are
a) CC0: (no cover crop or control check)
b) CC3: (mixture of annual ryegrass (Lolium multiflorum), Austrian winter pea (Pisumsativum (L.) Poir), and tillage radish (Raphanus sativus L.)
c) CC6: (mixture of annual ryegrass, Austrian winter pea, tillage radish, hairy vetch (Viciavillosa), buckwheat (Fagopyrumesculentum Moench), and oat (Avena sativa L.)
Six treatments will be: NT-CC0, NT-CC3, NT-CC6, and CT-CC0, CT-CC3, CT-CC6
2. Objective # 1. Develop a soil carbon balance (SCB)
The main approach to develop SCB is to account carbon additions in the soil and carbon released from the soil as CO2 and CH4 due to soil respiration. We are not separating root respiration and microbial respiration for this study.
a) Soil greenhouse gas (GHG) measurements: Soil collars (polyvinyl chloride; 8-inch diameter and 6.5-inch height) will be installed (2.5-inch deep) at each treatment plot at the beginning of the experiment. Collars will temporarily be removed prior to any management activities in the field. We recently purchased LI-7810 (CH4/CO2/H2O) and LI-7820 (N2O/H2O) Trace Gas Analyzers to measure in-situ greenhouse gas (GHG) emissions. However, we assume that net CH4 loss from the soil profile will be much lower than CO2 (Omonode et al., 2007) since South Texas soils remain dry during cotton-sorghum crop seasons. GHG sampling will be done every alternate day for two weeks before the cover crops are planted to get an average background data. After CC establishment, gas samples will be collected once a week throughout the CC growing season (90 to 100 days) and once a month afterwards till cotton and sorghum are harvested. However, intensive GHG sampling will be done after cover crop termination, fertilizer application and high rainfall. We have six treatments with four replications. Each sampling takes about 15 minutes: so, it would be around 6 hours (9:00 am to 12: pm) and (1:00 pm to 4:00 pm) of sampling for each sampling day. The timeline for agricultural practices is summarized in Table 1.
Table 1. Agricultural practices scheduled for this project
|
Season one and two |
September 2024 to August 2026 |
|
October |
Background gas emission data collection |
|
Late October to early November |
Cover crops are planted |
|
Middle of February |
Round-up will be applied to kill the cover crops |
|
Last week of February/early March |
Fertilizer application |
|
First or second week of March |
Sorghum planting |
|
Late March of early April |
Cotton planting |
|
Middle of July |
Sorghum harvesting |
|
August |
Cotton harvesting |
Composite soil samples for C analysis at depths of 0-5 cm, 5-10 cm, 10-30 cm, 30-60 cm, and 60-90 cm are selected to align with a future use of the DAYCENT model. Soil organic C analysis will be done at the beginning of the study period (October 2024) and end of the experiment (June 2026) to quantify the changes of SOC stock over time.
b) Total C contribution: Biomass of cover crops will be collected during harvesting. Total C (TC) of harvested, dried CC biomass and dried soil samples will be analyzed using a Carbon-Nitrogen Analyzer (LECO corporation) via dry combustion method. Field soil is alkaline, so, we expect significant amount of inorganic carbon will present in that soil. Since we will compare the data with background soil and control plots, we can interpret the amount of total carbon contributed by CC only and cancel out the free inorganic carbon at the experimental site. Note that we are not measuring root respiration or root C deposition for our SCB study as this would be beyond the scope of this study.
SCB (kg ha -1) = (TC contributed – TC released)
Where SCB is the Soil Carbon Balance in kg ha-1 and TC stands for total C (McDonald et al., 2019; Freidenreich et al., 2021).
- Objective # 2: Effect of meteorological parameters and soil physicochemical properties on SCB
The main purpose of this section is to develop the relationships between SCB and the factors affecting it. Meteorological parameters such as rainfall, temperature, relative humidity, and wind speed play important roles in affecting the GHG emissions from soil (Dattamudi, 2015; Dattamudi et al., 2019). Similarly, soil physicochemical properties such as gravimetric water content, water filled pore space (WFPS, %), bulk density, pH, CEC, are capable of influencing soil respiration (Freidenreich et al., 2022).
Meteorological data for this experiment will be collected from the Research station. Soil properties are being analyzed in another study at this plot will be used for our experiment.
Once we have the meteorological and soil data, we will use a Pearson’s correlation analyses to relate the variables (using SAS 9.4and JMP Pro v.14).
- Objective # 3: Knowledge dissemination activities
This objective will focus outreach activities and capacity building for the graduate student. Research outcomes will be presented at grower field days, extension activities, conference presentations, classroom demonstrations, and peer-reviewed publications. The student will present the study at Tri-Society (ASA-CSSA-SSSA) conferences and publish articles in peer-reviewed journal. Additionally, the graduate student will demonstrate this research to undergraduate students in Principles of Soil Science (PLSS 3410) class taught by his major professor. The student will also teach the TAMUK Soil Judging Team about soil health.
Annual report - updates on 04/11/2024
This project was recently set up and we started working on this project. But at this point we only have some pictures to share about our sample collection. Any analysis on those samples are yet to be done. Please see the pictures below.
Pictures of core sampling Pictures of greenhouse gas sampling