Soil biodiversity plays an important role in agroecosystems. Crop residue has several positive impacts on soil biological properties by providing an energy source for microorganisms, leading to greater microbial biomass and abundance. Residue retention favors fungal growth over bacteria and increases fungal populations under no-till systems. Macrofauna are also benefited as they burrow through residue and aid nutrient cycling. Conservation practices protect macrofauna from tillage impacts and allow them to mix organic material. Disease prevalence is reduced with greater biodiversity and soil moisture under residue retention systems.

1. LONG TERM IMPACT OF CROP RESIDUE ON SOIL
BIOLOGICAL PROPERTIES
Submitted by: Anju Bala
PhD 2nd year Agronomy

2. Soil Biodiversity
Plays a large role in agroecosystems by
affecting crop quality, occurrence of soil-
borne pests and diseases, nutrient cycling,
and water transfer.
1. Soil microflora (e.g. bacteria, fungi)
2. Soil fauna
i. Microfauna (e.g. nematodes,
protozoa)
ii. Mesofauna (e.g. acarids,
enchytraea)
iii. Macrofauna (e.g. earthworms,
termites, large arthropods).

4. Impact of crop residue on soil biological properties
Soil microflora:
• One gram of soil contain as many as 10 billion microorganisms and thousands of different
species
• Additional SOC through residue it provides an energy source for soil microorganisms and
lead to a greater microbial biomass
• Increase in SOC create a more favorable environment for the microbial populations due to
improvements in soil aggregation, soil moisture and/or more favorable soil temperature, this
can also improve microbial abundance.

5. Residue retention increase fungal population as compared to
bacteria:
• Tillage leads to the development of soil microbial communities
dominated by aerobic microorganisms with high metabolic rates,
typically bacteria.
• Whereas, under conservation practices, plant residues left at or
near the soil surface encourage fungal growth.
• Fungal-to-bacterial ratios are usually greater under residue
retained/no-till systems because there is less damage to fungal
hyphae due to little soil disturbance.

6. Macro-Fauna:
• Burrow through the soil and break up plant residues
• Important for the creation of soil microporosity
• Mix organic material into the soil to aid nutrient cycling and aggregate
formation
• The tillage operations in conventional agricultural systems can affect
macrofauna by directly killing or injuring them, by bringing them closer to
the soil surface and exposing them to adverse environmental conditions
and predators, and by destroying their food sources, burrows and tunnels.

7. Diseases:
• Increase in disease prevalence is much less.
• Improvements in biological diversity can increase the abundance of
micro-organisms that suppress diseases.
• The greater soil moisture often observed under residue retention may
lead to decreased plant moisture stress and reduced disease severity