Determining How the Ubiquitous Fungi Mortierella Regulates Belowground N Dynamics Under Different Crop Rotation Systems

View the project final report

Commodities

• Agronomic: cotton, grass (misc. perennial)

Practices

• Crop Production: catch crops, cover crops, cropping systems, crop rotation, irrigation, nutrient management
• Education and Training: extension, on-farm/ranch research, workshop, youth education
• Production Systems: agroecosystems
• Soil Management: soil quality/health

Nitrogen (N) is a main limiting factor for plant growth in agroecosystems. Given the unintended consequences for climate change and environmental impacts caused by highly inefficient N use in modern agroecosystems, increasing nitrogen-use efficiency in agriculture is a central focus of intensive research in agriculture. Mortierella elongata, a member of the early-diverging Mortierellomycota, is a dominant fungus among agricultural soils and functions as saprotroph and root endophyte, affecting several soil processes. Little is known about the effects of M. elongata on soil N transformation processes and the structure of the nitrifying community. Our preliminary results show that M. elongata isolates have a great ability to promote crop growth, but it remains unknown whether the promoting effects of M. elongata on crop growth are associated with its regulation of soil N dynamics and plant-available N. Our recent work shows that integrating two years of bahiagrass (Paspalum notatum) into conventional peanut (Arachis hypogea L.) and cotton (Gossypium hirsutum L.) cropping systems, known as sod-based rotation (SBR), has greater N availability compared with a conventional peanut-cotton-cotton rotation (CR). The proposed work focuses on a plant bioassay using cotton grown in soil from SBR and CR. We will combine stable isotope analysis with molecular tools to quantify the effects of M. elongata on microbially-derived N transformation processes and plant-available N dynamics, as well as on crop productivity under different crop rotations. Our objective is to better predict soil N transformations, helping growers improve economic viability with less external inputs while making agriculture more sustainable.

Objectives

1) Determine the molecular role of Mortierella in regulating soil N transformations and plant N dynamics under different crop rotation systems using ¹⁵N tracers;

2) Measure the effects of Mortierella on community structure and functional genes of the soil nitrifying microorganisms under different crop rotations;

3) Quantify the consequences of objectives 1 or/and 2 on cotton productivity.

Hypothesis

1) Mortierella induces higher plant-available N and soil N content and reduces N₂O emission under sod-based rotation (SBR) compared to conventional rotation (CR);

2) Mortierella increases the abundance and functional gene activity of the nitrifying community in SBR systems in comparison to CR;

3) The SBR system inoculated with Mortierella will have the highest cotton productivity.