Why Nutrient Replacement is Essential in Organic and all Agriculture Teagasc National Organic Conference 2 December 2008

1. Why Nutrient Replacement is Essential in Organic and all Agriculture Teagasc National Organic Conference 2 December 2008 Charles ‘Merf’ Merfield www.teagasc.ie www.merfield.com

2. The Schism Nutrient management in organics is an area of misunderstanding, confusion even dichotomy reaching back to the very beginning of organic agriculture. The Law of Return ‘vs.’ Closed System

3. The Law of Return Sir Albert Howard “An Agricultural Testament” 1943 “When man converts land to agriculture and harvests crops and livestock from the fields, mineral nutrients are removed from the soil. The failure of man to effectively return the waste products of agriculture back to the land results in mineral depletion of soil and represents a lost opportunity to build soil humus.”

4. Closed system • Lady Eve Balfour leading advocate and a fundamental question for the Haughley Experiment • That natural soil formation processes (pedogenesis), especially when speeded up by a biologically active soil, are more than sufficient to ensure that the fertility of soils are maintained or even increased

5. Closed cycle decedents • The debate was never concluded - Haughley Experiment ambiguous • The english speaking organic movements are Balfour’s philosophical and cultural heirs and inherited her position • UK Soil Assn created first english standards which set the ‘tone’ for most other standards

6. The Schism This has resulted in a widespread view of, and within, organics that ‘fertilisers’ are not needed. This is plain wrong. This is a ‘full and final’ explanation of why it is wrong… It is also a ‘bottom-up’ explanation of plant nutrition and nutrient cycles – from which agricultural nutrient management can be extrapolated

7. What are ‘nutrients’ • ‘Nutrient’ is shorthand for the chemical elements that living things are made of • Of the 94 naturally occurring elements, plants use only around 20 and animals around 30 (depending on the life form), although they often contain elements which have no biochemical function

8. COH96% 4% NPK3% Proportion of nutrients in plants

9. Un-reactive nitrogen in the atmosphere is converted by soil bacteria into reactive nitrogen in the soil which can then be taken up by roots Carbon & oxygengases in the atmosphere direct into leaves Hydrogen & oxygenas water (rain), from atmosphere, into soil then plant roots P, K, Ca, Mg, S, Fe, Cl, Mn, Bo, Zn, Cu, Mo, etc.,only from soil into roots Plant nutrient uptake pathways

10. Carbon, oxygen, hydrogen cycles Carbon Respiration Photosynthesis Oxygen

11. Nitrogen cycle!

12. N2 Nr Nr Nitrogen cycle N2 N2 Nr

13. Atmosphere P, K, Ca, Mg, S, Fe, Cl, Mn, Bo, Zn, Cu, Mo, etc., cycles Geological sediment uplift10 - 50,000,000 years + Rock weatheringThousands of years

14. Energy Closed Open Farm cycles and flows Carbon, oxygen, hydrogen, nitrogen Closed farm system Sales of crops and animals out the farm gate! Runoff and leachingAKA erosion Geological return10s of millions of years

15. Generalised soil nutrients behaviour Exported in produce and lost to erosion Soil parent material / bedrock Generally amounts in parent material determines if a soil is deficient, ‘balanced’ or has excessive (toxic) micro nutrient levels Medium availability typically as living and dead organic matter and bound in clay particles Rapidly available typically in soil solution (cations) on clay and humus Total soil: P = 1 – 2 tonnes / haK = 10 – 100 tonne / ha Plant available soil:P < 500 grams / haK < 20 kg / ha

16. What has changed? • Most of organic’s understanding of soil dates from the science of the 1930 – 1940s • The science of the origin of the chemical elements and their properties, plate tectonics, nutrient cycles, and soil chemistry, and particularly soil biology and ecology were only emerging at that time. • Most were not widely understood or accepted until the 1960 – 1970s even later

17. Why The Law of Return is correct • Howard based his analysis on empirical studies not theoretical analysis based on incorrect assumptions • He saw, just as we do today, that when nutrients removed in produce or via erosion are not returned to the land then after a period of years yields and quality decline.

18. Conclusions • The view of farms as closed systems (for anything) is completely wrong • All soil nutrients (non-atmospheric) removed from farm soils, by natural or human means, must be returned at the same rate at which they are removed if soils are not to become nutrient deficient. • The Law of Return is no theory, it is a Law.

19. Why Nutrient Replacement is Essential in Organic and all Agriculture Teagasc National Organic Conference 2 December 2008 Charles ‘Merf’ Merfield www.teagasc.ie www.merfield.com