Soil Quality Management and Assessment in Organic Agriculture

Transcription

1 Soil Quality Management and Assessment in Organic Agriculture Varughese Philip Agri-Food & Veterinary Authority of Singapore Soil Management Section Plant Health Laboratory Department Laboratories Group, 6 Perahu Road, Singapore

2 Organic farming aims to create an economically, socially and environmentally sustainable agriculture.

3 What is Soil Quality? There are several definitions Most older definitions link soil quality to some defined use of soil. Currently soil quality is more and more being equated to Soil Health

4 Soil Health Integration and optimization of the physical, chemical and biological properties of soil for improved plant growth. The foundation of organic farming systems rests on Soil Health Image credit: Cornell Soil Health (Adapted from the Rodale Institute).

5 Organic Farmers have for long sensed soil quality from the way soil feels.. from how the soil smells.. from how the soil looks.

6 Soil continuum and the key driver in Organic Agriculture Soil Physical condition Organic Matter Soil Fertility Soil Biology

7 So what holds it together? Soil organic matter - Increase soil nutrient reserves. - helps bind soil particles - increases nutrient and water-holding capacity - Change soil nutrient supply processes. - Changes to the soil physical attributes. Organic Carbon 2% Total Organic Carbon 26 t/ha Soil depth 0.10 m Bulk Density 1.3 g/cm 3

8 Carbon cycling / Organic matter degradation CO energy O 2 2 Plant Debris Fungi Earthworms Bacteria Soil Humus Image credit: soils.stanford.edu

9 Soil Physical Condition Is the soil well structured? - aeration - drainage Does it have good aggregate /crumb structure? - moisture holding - root penetration / access to nutrients Affected by the original soil type and by soil management?

10 Soil structure Affects Soil density and Water Movement. Both these have a bearing on root growth. Image credit:

11 Tillage Current organic systems usually require tillage prior to planting and sometimes even after planting Tillage destroys OM that is critical in improving soil fertility and soil water-holding capacity. Tillage should be performed when soil moisture is low enough to prevent compaction.

12 Soil Fertility Soil fertility - Measure of the soil s ability to sustain satisfactory crop growth both in the short and long term. Fertile soil provides essential nutrients to plants, while supporting a diverse and active biotic community

13 Soil Fertility in Organic Farming Systems Organic producers face unique challenges in managing soil productivity. Organic farmers rely on observation, advice from other farmers, conventional soil tests, and their own experience to make decisions about the quantity and types of soil amendments to apply

14 Soil Fertility in Organic Farming Systems Big variability in nutrients applied and the resulting soil fertility on organic farms Current guidelines on nutrient management for organic farmers are fairly general in nature.

15 Soil Fertility in Organic Farming Systems Building Soil Fertility Nutrient Sources Fixation Crop residue Cover crop recycling Added organic matter Rainfall Nutrient Losses Leaching Volatalisation Emissions Removal through crops Exported manures / residues In the organic farming system There would be alternating fertility building and fertility depleting phases

16 Soil Fertility in Organic Farming Systems All organic systems will require supplementary nutrients to replace those removed from the farm How to decide what to supplement? Do farms / farmers understand the concept of nutrient budgets?

17 Information needed for Assessing Soil Quality Physical Bulk Density, Texture, Wet Aggregate stability, Surface hardness, AWC Chemical ph, Nutrients Biological Organic C, Active C, Microbial biomass C, PMN, Microfauna, Microflora, Root health assessment

18 Information needed for Assessing Soil Quality Traditionally - Only soil nutrient availability was assessed through chemical analysis Now physical and biological parameters are also included in assessments of soil quality

19 Information needed for Assessing Soil Quality Indicators Loosely defined as those soil properties and processes that have greatest sensitivity to change in soil function.

20 1. Indicator Selection Minimum Data Set Indicator Indicator Indicator Indicator 2. Interpretation Minimum Data Set Score Score Score Score 3. Integration Index Value Conceptual Framework for the Soil Management Assessment Tool After Andrews, 1998)

21 SQI For Soil Health (SH) AVA, Singapore is collaboration with Cornell University to develop SH indicators for vegetable farms in Singapore

22 1. Does the organic farming community have access to technical resources needed for management decisions? 2. Are current soil quality assessment methods skewed towards conventional agriculture or do they adequately reflect the status of organic agriculture?

23 Conventional Chemical Soil Testing in Organic Farming Systems Conventional Testing & Recommendation based on years of research and experience. Representative sample is from a large area. Sampling time is in calendar years. Nutrient extraction methodology Calibrated Organic Due to complexity of organic systems, testing methodology and interpretation needs reconsideration May require more intense sampling due to diversity of crops, rotations and microflora. Sampling to be site specific and to correlate with crop sequence. Nutrient extraction is complex due to interactions and is less studied as of now

24 Acknowledgement I thank the organising committee for inviting me to the Forum and am deeply honoured for the opportunity to speak. My thanks to the Director, Plant Health Laboratory Department and Senior Management of AVA for approving my participation in this Forum.

25 Thank You