Turning the CorNer
Almost following on from my last blog post with this one so please switch off if your tired already, I won’t be offended!.
The C:N is the amount of soil organic carbon (SOC) to nitrogen ratio in the soil. SOC is not to be confused purely with thatch levels, there is good organic matter (OM) and bad OM. The C:N ratio is all about carbon and nitrogen cycling through the natural means of the soil microbial. Getting the C:N balance to a higher ratio and stabilising the relationship between the SOC and the soil biology is paramount and will reap rewards in the soil by giving the soil microbial the food and environment it likes to thrive. The little greenkeepers will do a lot of the work keeping the thatch levels to a sensible level without the need to pull cores, thus not disturbing the biology more and keeping the symbiosis between plant and soil saving a few quid on the feeding programme which is essential with rising costs. From an environmental perspective pulling cores is releasing carbon faster as once its removed and meets all that oxygen it breaks down fast, so why not let nature help out and break it down at a pace it was designed and the natural plant food in the soil also reduces need for fertiliser so reduces another greenhouse gas called nitrous oxide (N20).
At Phoenix we have had a lot of years feeding high mineral nitrogen granular feeds that a) interfere with the symbiosis and change the natural soil biology type to a more unfavourable one over time and b) cause an imbalance in the C:N ratio by increasing both carbon in the surface of our greens from turf organic matter production and nitrogen from the high mineral granular feed applied. As the soil biology decreases so does its productivity, then we have to apply lots of sand in order to dilute the OM produced by the high nitrogen feed causing excess growth in the turf and this inert material with a high bulk density also has a negative impact on biology. It’s easy to see how you can end up chasing your tail in the circle of decline. More feed = less biology = more thatch produced and less broken down so = more coring = apply more sand = apply more feed for recovery = back to square 1. All sounds expensive and counter intuitive to me.
In a natural soil like a forest this soil foodweb happens without intervention from man with “a bag per tree” of granular fertiliser. The tree litter drops to the floor where worms, Protozoa, fungi and bacteria break it down, nematodes feed on the good guys (and the bad) releasing food and other nitrogen fixing bacteria turn it back as plant food in an available form of Nitrogen. When there is little food available the fungi stretch there legs to find this food deeper down to give it to the plant. All the bacteria and fungi want in return are the sugars, amino acids and organic compounds given off as exudates from the plant roots. This symbiosis keeps everything balanced in the soil without need for intervention and has been happening since plants and bacteria were on the planet. The difference with a purely natural soil like a forest and our putting greens, is that we’ve already interfered with nature by cutting at low heights that stress the turf and by walking over a small area constantly causing compaction we need mechanical intervention with our tractors to alleviate and apply a little feed to keep the growth to a steady rate to help with recovery of all that wear.
Since my appointment I’ve concentrated on reversing some of the negative effects in order to increase the C:N ratio of our putting green soils and increase soil microbial mass and diversity. This should also increase the chance of perennial grasses establishing making it harder for the annual disease prone grasses to gain the upper hand and also gain protection from diseases by root colonising biology wanting those exudates. I’ve stopped pulling hollow cores with only positive effects on the OM in the top 25mm (which is where it matters from a playability point of view), I’m applying less sand, I’ve cut granular mineral fertiliser a lot and only use organic granular, I now apply more liquids feed to the leaf, I’ve cut annual N amounts and apply more carbon high substances like seaweed, humic acids and fish hydrolysate in with my biology spray of compost tea. Next year I will feed by minimum levels for sustainable nutrition (MLSN) and by GP model. All this which means no excess nutrients are applied that the grass doesn’t need and any Nitrogen amounts are judged by how much the plant needs to grow at that time.
It’s no easy task by any means and one that will take a while but once nature is working as it should, I can back off from applying the little greenkeepers in my compost tea and natural selection will take over in the soils microbial diversity. I’m already seeing C:N at an half decent ratio but there’s room for improvement and we will keep at it. In today’s world where climate change and carbon is a big issue, carbon sequestration shouldn’t be missed on the golf course either