Improving semi-arid agroecosystem services with cover crop mixes

Area of Science:

• Agricultural Science
• Soil Science
• Agronomy

Background:

• Winter wheat production in the semi-arid Northern High Plains faces drought and poor soil fertility.
• Composted manure and cover crops offer agroecosystem services but cover crops may deplete soil moisture.
• The impact of cover crops on soil health in compost-amended, low-moisture soils in this region is not well understood.

Purpose of the Study:

• To evaluate the effects of compost-amended cover crop treatments on soil properties, carbon and nitrogen content, and biological nitrogen fixation (BNF).
• To assess weed presence and biomass under different cover crop and amendment regimes.
• To determine if cover crops can enhance agroecosystem health without compromising soil water content in a challenging environment.

Main Methods:

• Four cover crop treatments (Mycorrhizal Mix, Nitrogen Fixer Mix, Soil Building Mix, Phacelia monoculture) were grown in greenhouse conditions with native soil at 7% moisture.
• Treatments were amended with either compost (45 Mg ha-1) or inorganic fertilizer (IF).
• Measurements included soil and plant total carbon and nitrogen, biological dinitrogen fixation (BNF), weed biomass, and germination rates.

Main Results:

• Compost amendment with Mycorrhizal Mix resulted in the highest BNF (48 g m-2) and soil carbon increase (1.7%).
• Soil Building Mix showed the highest germination and aboveground biomass, reduced weed biomass by 60%, and achieved 40 g m-2 BNF with a 1.5% soil carbon increase.
• Inorganic fertilizer significantly reduced BNF by nearly 70% in legume-containing cover crops and decreased soil carbon by 15%.

Conclusions:

• Compost-amended cover crops, particularly Mycorrhizal Mix and Soil Building Mix, can enhance soil carbon and nitrogen fixation in water-limited conditions.
• Cover crops can effectively suppress weeds, contributing to improved agroecosystem health.
• Inorganic fertilizers are detrimental to biological nitrogen fixation and soil carbon in this context, highlighting the benefits of organic amendments.