DAY FOUR: On farm with Tim Smith in Eagle Grove, Iowa

Tim participates in federal programmes like the National Resources Conservation Service and the Mississippi River Basin Healthy Watersheds Initiative. He has half a million acres in these sorts of programmes to reduce nitrogen and phosphorus loading in the Gulf of Mexico via the Boone river, Des Moines river and the Mississippi river in this farm’s case. Where land is drained, some use of tillage is more common but using a chisel plough or disc ripper instead of mouldboard plough. Excessive rain leads to poor crops where water stands, which they call a 'drown out area’ – so it seems it pays to have drainage, but is also a conduit for nutrient escape.

Cover crops, nutrient management, strip-tillage and a wood chip bio reactor have been implemented or tried in experiments, especially where land is tile drained, to reduce nitrate. Cover crops sequester nitrogen from soil as Organic Matter and carbon - university studies indicated 30 per cent of available nitrates can be picked up by rye. Oats are less efficient in this partly because they die in winter.

US Geological Survey has 15 nitrate sampling sites, detecting losses of 37lbs nitrogen per watershed acre - some years more, some less – stable soils are another benefit of catch and cover crops. Catch crops on Tim’s farm were seeded with aircraft at the end of August while soya was green, but it can be applied with high-boy pneumatic spreader on a sprayer chassis with a ground drive at a speed of 50 acres an hour. It costs $14 an acre to seed aerially and rye seed costs are $28 an acre and $10 an acre radish. There is a cost to terminate rye, but radish and oats die in the cold, pre-emergence herbicides would be used anyway. Federal program covers 100 per cent of costs in the first year.

Some farms put Anhydrous Ammonia on in autumn. ‎Putting cover crops in and delaying nitrogen helps reduce escape but it carries the risk that the crop will be short in spring.  Some drains have a wood chip underground bed bio-reactor, like a mini wetland, which is a carbon source for naturally occurring bacteria to colonise. It costs $6-10K, click here to see one paid for by Sam Walton foundation – a charity WalMart has put in place. It would be replaced after 10-15 years and would not need water control gates then so it’s likely that just the wood chips would need replacing. It’s located alongside streams under buffer strips or even farmed land and the systemsinvolves small mechanical control gates to bypass some water to avoid backing up drain.

There is bi-weekly or weekly testing of water out of tile drains for nitrogen on Tim’s farm – he’s taking action for data now to avoid future regulation. The alternative to bioreactor is perpendicular drains higher in soil profile within filter strip by edge of filed, half depth at 2 inches and are 1000 inches long‎ to pass water through soil again slowly before it reaches the stream. Oxbows are used as mini wetland ponds near stream at half an acre to allow further denitrification. Dual ecosystem supports fish and other biodiversity.