Cover Crop Systems Impact on Biomass Production, Carbon-to-Nitrogen Ratio, Forage Quality, and Soil Health Indices in a Semiarid Environment.

Arid and semiarid agroecosystems of the United States are characterized by perennial challenges of water deficiency including low soil moisture retention, poor soil fertility, and vulnerability to both wind and water erosion. A soil restorative strategy that has been widely practiced to protect and enhance soil physical, chemical, and biological properties is cover cropping. The integration of cover crops into cropping systems has reduced soil erosion and agrochemical runoff, increased water infiltration rate and storage, and provide abundant organic residues to enhance the biological and physical qualities of soils for crop production. We hypothesized that cover crop mixtures will produce greater above- and below-ground biomass and forage nutritive value and lower tissue carbon-to-nitrogen (C/N) ratios. We also hypothesize that these characteristics will promote greater soil organic carbon, total nitrogen, and microbial biomass and diversity compared to cover crop monocultures. Consequently, the objectives of this 2-yr study were to (i) quantify the above- and belowground biomass production, forage nutritive value, and tissue carbon and nitrogen concentrations from different annual cool-season cover crop systems, and (ii) to determine their effects on soil organic carbon, total nitrogen, soil respiration, and soil microbial population biomass. This study was carried out on an Orr sandy loam at the Valley Road Field Laboratory, University of Nevada, Reno. Treatments (n = 8) used were a fallow, monocultures of annual ryegrass (Lolium multiflorum Lam.), oat (Avena sativa L.), faba bean (Vicia faba L.), yellow sweetclover [Melilotus officinalis (L.) Lam], winter pea (Pisum sativum L.) and two three-species mixtures (Cover crop mixture 1 [Mix 1]: annual ryegrass + faba bean + yellow sweetclover and Mix 2: Oat + faba bean + winter pea) laid out in a randomized complete block design 0with three replications. Averaged across years, Mix 2 produced greater biomass (9714 kg DM ha-1; SE = 699) than all other cover crop systems except, the monoculture of oat (7970 kg DM ha-1; SE = 699). The C/N ratio of the mixtures and monoculture legumes was mostly similar (range = 19.4 - 29.1; SE = 3.3). Legumes overall produced superior forage quality (RFV range = 112 - 161) compared to grass monocultures and mixtures (RFV = 80 - 95). Soil gram-negative bacteria biomass was greatest under the yellow sweetclover monoculture. Overall, the mixtures offered a superior balance to meet the dual role of soil health improvement and feed quality for livestock in this semiarid environment.Keywords: Biomass, carbon-to-nitrogen ratio, cover crop, forage quality, microbial biomass, soil respiration, soil organic carbon, and soil total nitrogen

Level thesis:degree_level

Master's Degree

Year dc:date.issued

2022

Author dc:creator

• Opoku, Akwasi

Advisor dc:contributor.advisor

• Solomon, Juan K. Q.

Committee members dc:contributor.committeemember

• Payne, William A.
• Rodriguez, Alejandro A.
• Washington-Allen, Robert A.
• Fonseca, Mozart
• Verburg, Paul

• Biomass
• Conservation Agriculture
• Cover crops
• Nutritive value
• Semi arid environment
• Soil

Statement dc:rights

• Creative Commons Attribution 4.0 United States

Handle dc:identifier.uri

http://hdl.handle.net/11714/8417

OAI identifier oai:identifier

oai:scholarwolf.unr.edu:11714/8417