Sowing oil radish as a green cover crop after peas has produced promising results for Adrian Ivory of Strathisla Farms in Perthshire, with a noticeable difference in soil structure and impressive nutrient capture.
 
Mr Ivory looks after 2500 acres of Perthshire land, growing winter wheat, winter and spring barley grass for cattle grazing and leasing land to others for peas and potatoes. In a bid to improve soil structure and mop up any nitrogen left behind by the peas, he chose to grow green cover crops in an arable rotation for the first time.
 
Oil radish was sown at 20kg/ha during late July and early August. The cover crop was planted in three whole fields, one going into winter wheat and two into spring barley. The latter had the additional aim of reducing leaching.
 
“The fields are down by the river which quite often floods, so we wanted a crop in the ground that would hold the soil together, stop it washing off and put goodness back into the soils too,” says Mr Ivory.
 
Two more fields destined for winter wheat were half sown with oil radish, comparisons of which will help to highlight the crop’s benefits on the farm. Mr Ivory highlights that he didn’t spend too much time or use complicated techniques to establish and manage the cover crop, using a fertiliser spreader in some fields before grubbing and rolling and a borrowed grass seed drill for others. No fertiliser was applied either: “It was a cost we didn’t need,” he says simply.
 
Having chopped the oil radish down to 6” two days before the green material was ploughed in in October, winter wheat drilling was completed in early November. Mr Ivory has already noticed a difference in soil structure where the oil radish was grown.
 
“Where moisture usually lies on the field, the radish has utilised it and the soil is much more broken up and friable, so the seedbed is fantastic,” he explains.
 
A fresh weight cutdown taken before the crop was chopped and ploughed in showed that the crop had taken up over 100kgs/ha of nitrogen.
 
“I was fairly surprised at the data that came back, and impressed,” explains Mr Ivory. “Peas are known to fix nitrogen in the soil, although we weren’t sure how long after harvest it would be fixed for. We can’t be sure yet how much of the N that was captured will go into the following crop, but it’s looking promising at the moment.”
 
Mr Ivory was advised by Kings technical advisor in Scotland, Alan Johnson who was recommended by his Frontier farm trader, Callum Mackintosh.
 
“These are good results,” states Mr Johnson. “The crop acted like a sponge to mop up and hold all of that nitrogen. If the land was left bare over that time and heavy rain fell, there’s potential that some of that N would likely have leached away, which is bad for the environment and a waste of valuable resource too.”
 
In addition to the long term benefits to the soil and crop performance, Mr Ivory is keen to explore whether adjustments can be made to fertiliser rates as a result of the nutrient capture too.
 
 “Yield mapping on the combine next harvest will help to confirm the overall impact of the oil radish, but things are definitely looking good at the moment,” Mr Ivory concludes.