1 Iron Stabilization of Crop Residues as a Novel Land Management Practise for Sequestering Carbon in the Agricultural Sector Geoff Whiteley School of Biology, University of Leeds, UK Third USDA Symposium on Greenhouse Gases and Carbon Sequestration in Agriculture and Forestry March 22-24, 2005, Baltimore, Maryland

2 Novel concept Current strategies to increase sequestration of carbon in the agriculture sector are dependent on shifting the balance between established systems of conventional land management e.g. afforestation of crop and pasture land or shifts from conventional to conservation tillage Access to financial incentives for carbon storage might stimulate innovation in the sector and encourage alternative or new residue management technologies, if they can be shown to have verifiable effect on stored carbon Iron stabilization of field crop residues is considered in this context

3 Aims of this presentation What is iron stabilization? Current uses of the technology in horticulture Some effects on earthworm feeding and nitrogen mineralisation Scaling up – how a farm process might work Carbon sequestration potential in agricultural soils Economic feasibility – treatment costs in relation to amount of net carbon stored in soils and litter Conclusions

4 Iron stabilization in horticulture Iron mineral impregnation of crop biomass is used in horticulture to slow the rate of decomposition of materials such as wheat straw MulchesGrowing media Processing of wheat straw for use in consumer and professional garden mulches: Stability in storage as a packaged product Coloration to add value Extended product life in situ Pulverized biomass including wheat straw as a constituent for reduced peat and peat replacement products : Reduced nitrogen immobilization Color and stability

5 Iron stabilization in horticulture Iron mineral impregnation of crop biomass is used in horticulture to slow the rate of decomposition of materials such as wheat straw Mulches Processing of wheat straw for use in consumer and professional garden mulches: Stability in storage as a packaged product Coloration to add value Extended product life in situ Sold in the UK as Strulch ®

6 Growing media Pulverized wheat straw can be converted into a more useful form for use in the manufacture of reduced peat and peat replacement products : Reduced nitrogen immobilization Color and stability Currently under development Iron stabilization

7 C and N mineralisation The effects of wheat straw Triticum aestivum L. incorporated in 3 different particle sizes (fine [FN], medium [MD] or. coarse [CS]) and treated with iron at (0.0g/100g [00], 0.4g/100g [04] or 0.8g/100g [08]) on ryegrass Lolium multiflorum gowth and nitrogen uptake over 120 days. Iron bonding to cell wall polymers creates a physical and chemical barrier to access by cellulose degrading enzymes, with the increased recalcitrance contributing to reduced microbial nitrogen immobilisation and an extended life for surface applied mulching layers.

8 Palatability Amount of each foodstuff extracted by L. terrestrisin in a choice chamber experiment containing aged wheat straw (C), plus mineral iron (M), plus nitrogen (NC) and plus mineral iron and nitrogen (NM).The error bars are standard errors of the means. Addition of iron can also reduce palatability to earthworms. Residual after soil incorporation can be shown in the persistence of crop residue fragments in the light fraction of soil organic matter and a Fe-stabilized humic material.

9 Possible carbon sequestration potential of a single spray treatment of 6 kg of Fe per metric ton of wheat straw applied after harvest This example shows the higher of three scenarios for efficacy of the iron treatment on the retention of biomass.

10 Carbon equivalence over the sequestration period Transformed data, again for the higher of three scenarios

11 Increased carbon retention per metric ton of treated straw

12 Net carbon storage from one metric ton of treated straw Rental payment income were then calculated for net sequestration, using a 5% discount* rate for payments ranging from $10 to $150 per metric ton of permanent carbon sequestration. *Source: Economics of Sequestering Carbon in the US Agricultural Sector TB-1909 Economic Research Service/ USDA 2004.

13 Sequestration rental value Over the 15 year projection, the net increase in stored carbon ranged from 0.33 metric tons per metric ton of treated crop residue in the high scenario with conservation tillage to metric tons per metric ton of treated crop residue in the low scenario with conventional tillage. Increased residue cover in the first year after treatment accounted for between 38% and 52% of the total increase in carbon retention under conservation tillage and net storage remains correspondingly higher under conservation tillage than conventional tillage. Rental values never exceeded $2.50 per metric ton of treated crop residue, representing only a proportion of the cost materials purchased.* *The supply of materials for a single application was taken to be $8.00 per metric ton of treated straw (assuming a delivered price of $200 per metric ton of ferrous sulfate).

14 Protected biomass value? What is a ton of retained crop residue worth to a grower in a zero till system? Erosion protection Increased organic matter in some soil types Effects on nitrogen mineralisation Accumulative effects through year on year use Effects on yield The supply of materials for a single application was taken to be $8.00 per metric ton of treated straw.

15 Conclusions It appears unlikely that incentive payments will influence decisions by farmers to use the technology The process may have intrinsic worth where crop residue are limiting factors to productivity Large scale take up of the technology on a regional scale might still be shown to have a measurable impact on carbon stocks in the agricultural sector Sequestration income could fund administrative costs for partnership projects

16 IP Routes for exploitation Ingwermat Limited University of Leeds Licensee This presentation is based on information published in United States Patent 6,318,021 Whiteley, G M November 20, 2001 Agriculture sector sub-licensee R & D Partnerships Collaborative projects and demonstrations Implementation