Location: Columbia Plateau Conservation Research Center
Project Number: 2074-11120-005-000-D
Project Type: In-House Appropriated
Start Date: Oct 1, 2021
End Date: Sep 30, 2026
Objective:
Objective 1: Quantify impact of intercropped legume cover crops with winter wheat to increase soil carbon and reduce herbicide and synthetic nitrogen (N) fertilizer inputs.
Sub-objective 1.A: Identify the best performing legume cover crops for intercropping with winter wheat that reduces herbicide and synthetic N while improving precipitation use efficiency in intermediate rainfall zones.
Subobjective 1.B: Examine whether legume cover crop intercropped with winter wheat can increase soil organic carbon (SOC), reduce herbicide and synthetic N fertilizer inputs, and reduce CO2 and CH4 emissions.
Objective 2: Measure deep root-zone water dynamics in dryland cropping systems to optimize water storage with tillage, crop residue, cover crop, and weed management.
Objective 3: Examine the use of biostimulants and biochar (such as thermal carbonized manure) as amendments in dryland wheat production systems in order to improve soil and plant health, profitability, and resilience to extreme weather and climate change.
Sub-objective 3.A: Establish whether the addition of biostimulants to soils can enhance plant growth and soil properties to reduce drought stress under semi-arid dryland wheat production conditions.
Sub-objective 3.B: Determine whether the addition of thermal carbonized manure to soils can increase soil pH in the N fertilizer application zone and enhance plant nutrient uptake under semiarid dryland wheat production systems.
Approach:
1.A. Establish intercropped wheat with 4-legumes. Determine grain yields and wheat, legume, and weed biomasses. Apply herbicides while control subplots are covered to count weeds per species. Collect soil samples at the start of the experiment and after the 4th growing season. Determine total, organic and inorganic C, and N; and extractable P, NO3-N, and NH4-N. Collect soil samples for in-season N fertilization and determine dissolved and labile C and N at the time of N fertilization and at harvest. Monitor soil temperature and water. Collect CO2, N2O, and CH4 samples for two years. Perform life cycle analysis (LCA) from greenhouse gas (GHG) emissions from (1) diesel combustion at each stage of crop production, delivery of seed, fertilizers, pesticides, and (2) direct field emission of GHG.
1.B. Measurements are made in 1) wheat-fallow under reduced tillage, 2) no-till annual winter wheat, and 3) no-till wheat–wheat–sorghum/sudangrass. Half of the plots are planted and managed using herbicide. The other plots are intercropped with a legume. Monitor solar radiation with Albedometers. Collect soil samples and determine total and labile C and N as in 1.A. Soil temperature, water and GHG will be monitored, and the LCA will be performed as in 1.A.
2. Install soil water sensors below tillage depth in controlled experiments on post-harvest weed control, alternative crops, cover crops, and in farmer’s fields of selected management practices. Install sensors in 5-cm boreholes to monitor the root zone and below the root zone to detect upward and downward water movement. A minimum of 24 profiles under commercial farm practices in different locations are monitored for the soil and yield response to precipitation events, weed growth, and cropping patterns. Soil water storage, water extraction by the crop, and yield are principal measurements. The data is posted online in real-time.
3.A. Plots of no-till continuous wheat-wheat with 3-N fertilizer rates (0, 50, 100 kg N/ha) will be used. Apply biostimulants to 4 subplots within the N main plots at a rate of 3.7 L/ha at the 4th leaf growth stage. Grain, biomass yields, and harvest index are determined. Shoots and roots are sampled at V6 & maturity and stored (- 80°C) until analyzed. The samples are extracted and analyzed for up to 18 endogenous plant hormones, 8-carbohydrate and 11 phenol monomers. Carbohydrate monomers are hydrolyzed by H2SO4, separated by anion chromatography, and detected by pulsed amperometry. Phenol monomers are extracted by CuO oxidation and NaOH hydrolysis and detected by GC. Amino acid monomers are extracted, separated by anion chromatography and detected by pulsed amperometry.
3.B. Poultry litter will be pyrolyzed and compared with conifer wood and wheat straw biochars and replicated plots will be treated with each of the 3 biochars and incorporated by rotary tillage. Soil cores will be collected before and after application of the biochar. Total soil N, S, and C, extractable NO3 and NH4, micro- and macronutrients, soil pH, and EC are determined. Winter wheat will be seeded by hand for 3 yrs. Micro- and macronutrients in the wheat grain and straw will be determined at harvest.
