Uploaded August 2026 | Updated September 2026, 3 days ago
Does agricultural lime solve low soil pH—or does the living root zone deserve more attention?
Dr Mary Cole explains how the rhizosphere, root exudates and mycorrhizal fungi may influence nutrient availability and pH immediately around living plant roots.
Tim Thompson sits down with Dr Mary Cole of Agpath in Victoria to examine one of the most debated questions in soil management: when should farmers apply lime, and when should they look more closely at soil biology, calcium cycling, living plant cover and conditions around the roots?
Mary challenges the routine use of agricultural lime and explains her biological-farming perspective on:
• Bulk soil pH versus conditions within the rhizosphere
• Why plant nutrient requirements change during growth
• How root exudates communicate with soil microorganisms
• The exchange of plant carbon for nutrients such as phosphorus
• How mycorrhizal fungi extend the area explored by plant roots
• Glomalin, soil aggregation and soil carbon
• The proposed role of fungal oxalates around living roots
• Why continuous plant cover matters for soil biology
This discussion is useful for pasture farmers, croppers, livestock producers, regenerative farmers, small landholders and anyone investigating low soil pH, soil acidity, agricultural lime or nutrient availability.
Farmers researching how lime works, when to apply lime, calcium availability, rhizosphere biology, root exudates, mycorrhizal fungi, glomalin, biological farming, living roots, pasture soil health and regenerative agriculture will gain a clearer understanding of the difference between the bulk soil measurement and the biologically active soil immediately surrounding plant roots.
This video presents Dr Cole’s biological-farming perspective. Liming decisions should still be based on representative soil sampling, the pH testing method used, soil depth, soil buffering capacity, lime quality, production goals and appropriate local agronomic advice.
Watch next on Farm Learning:
• Soil Food Web: How Protozoa Release Plant Nitrogen
• How root exudates connect plants with soil microorganisms
• Mycorrhizal fungi, glomalin and soil aggregation
• Soil Biology, Compost & Biological Inputs playlist
Subscribe to Farm Learning with Tim Thompson for practical agricultural education based on farmer experience, field observations, technical explanations and conversations with agricultural specialists.
Share this video with a farmer, contractor or landholder working through soil acidity or repeated lime applications. Leave a comment explaining what soil tests, plant responses or field observations you use before deciding whether to apply lime.
DETAILS
Location: Victoria, Australia
Guest: Dr Mary Cole
Organisation: Agpath
Topics: Soil pH, agricultural lime, soil acidity, rhizosphere biology, root exudates, mycorrhizal fungi, glomalin, calcium availability and continuous living cover
#SoilPH #SoilBiology #RegenerativeAgriculture #MycorrhizalFungi #farmlearning
00:00 Does Low Soil pH Always Need Lime?
00:21 The Standard Lime Recommendation Challenged
00:44 Fifty Years Without Synthetic Inputs
01:11 Why Repeated Lime Applications Are Questioned
02:10 Bulk Soil pH Versus Root-Zone Conditions
03:01 How Root Exudates Signal Nutrient Demand
04:04 Mycorrhizal Fungi and Phosphorus Access
04:52 Glomalin, Soil Carbon and Aggregation
05:52 Fungal Oxalates and pH Around Roots
06:12 Living Plant Cover: The Practical Takeaway
Does agricultural lime solve low soil pH—or does the living root zone deserve more attention?
Dr Mary Cole explains how the rhizosphere, root exudates and mycorrhizal fungi may influence nutrient availability and pH immediately around living plant roots.
Tim Thompson sits down with Dr Mary Cole of Agpath in Victoria to examine one of the most debated questions in soil management: when should farmers apply lime, and when should they look more closely at soil biology, calcium cycling, living plant cover and conditions around the roots?
Mary challenges the routine use of agricultural lime and explains her biological-farming perspective on:
• Bulk soil pH versus conditions within the rhizosphere
• Why plant nutrient requirements change during growth
• How root exudates communicate with soil microorganisms
• The exchange of plant carbon for nutrients such as phosphorus
• How mycorrhizal fungi extend the area explored by plant roots
• Glomalin, soil aggregation and soil carbon
• The proposed role of fungal oxalates around living roots
• Why continuous plant cover matters for soil biology
This discussion is useful for pasture farmers, croppers, livestock producers, regenerative farmers, small landholders and anyone investigating low soil pH, soil acidity, agricultural lime or nutrient availability.
Farmers researching how lime works, when to apply lime, calcium availability, rhizosphere biology, root exudates, mycorrhizal fungi, glomalin, biological farming, living roots, pasture soil health and regenerative agriculture will gain a clearer understanding of the difference between the bulk soil measurement and the biologically active soil immediately surrounding plant roots.
This video presents Dr Cole’s biological-farming perspective. Liming decisions should still be based on representative soil sampling, the pH testing method used, soil depth, soil buffering capacity, lime quality, production goals and appropriate local agronomic advice.
Watch next on Farm Learning:
• Soil Food Web: How Protozoa Release Plant Nitrogen
• How root exudates connect plants with soil microorganisms
• Mycorrhizal fungi, glomalin and soil aggregation
• Soil Biology, Compost & Biological Inputs playlist
Subscribe to Farm Learning with Tim Thompson for practical agricultural education based on farmer experience, field observations, technical explanations and conversations with agricultural specialists.
Share this video with a farmer, contractor or landholder working through soil acidity or repeated lime applications. Leave a comment explaining what soil tests, plant responses or field observations you use before deciding whether to apply lime.
DETAILS
Location: Victoria, Australia
Guest: Dr Mary Cole
Organisation: Agpath
Topics: Soil pH, agricultural lime, soil acidity, rhizosphere biology, root exudates, mycorrhizal fungi, glomalin, calcium availability and continuous living cover
#SoilPH #SoilBiology #RegenerativeAgriculture #MycorrhizalFungi #farmlearning
00:00 Does Low Soil pH Always Need Lime?
00:21 The Standard Lime Recommendation Challenged
00:44 Fifty Years Without Synthetic Inputs
01:11 Why Repeated Lime Applications Are Questioned
02:10 Bulk Soil pH Versus Root-Zone Conditions
03:01 How Root Exudates Signal Nutrient Demand
04:04 Mycorrhizal Fungi and Phosphorus Access
04:52 Glomalin, Soil Carbon and Aggregation
05:52 Fungal Oxalates and pH Around Roots
06:12 Living Plant Cover: The Practical Takeaway
