With bagged ammonium nitrate fertiliser costs rising above £600/t, soil mineral nitrogen testing has change into important for one Hampshire farm supervisor as he seeks to optimise vitamin throughout all his crops.
Charlie Batten used a spread of spring nitrogen charges, from 130kg/ha to 240kg/ha, on his oilseed rape final 12 months.
This highlighted how simply nitrogen might be wasted in case you don’t examine how a lot of the dear nutrient is already within the crop and soil.
Mr Batten is south-east regional farm supervisor for administration group Velcourt, and he sees early-season soil testing for cereals and rapeseed as very important to examine if soil nitrogen provide is larger than regular following the dry and gentle winter this 12 months.
Whether it is, he can tailor nitrogen fertiliser charges to the crop’s wants.
“The excessive value of nitrogen emphasises how necessary it’s to get soil testing right. It’s not about slicing nitrogen, however reaching the optimum charge,” he tells Farmers Weekly.
See additionally: How assessments for moreover accessible N can reduce fertiliser use
Charlie Batten and William Baldwin (proper) © David Jones
Throughout the 180ha of oilseed rape he grows at House Farm, West Tytherley, on the Hampshire-Wiltshire border, Mr Batten manages nitrogen utilizing a cover administration strategy.
The spring charge of stable ammonium nitrate in 2021 was within the 110kg/ha vary, relying on soil mineral nitrogen ranges and crop biomass.
- Based mostly at House Farm, Norman Court docket, West Tytherley
- Soils – predominantly chalky loams over chalk, with clay caps and a few flints
- Farms 2,700ha from north of Andover right down to the coast close to Lymington, rising winter wheat, winter barley, spring barley, spring oats and oilseed rape
Some ahead crops can see financial savings on costly nitrogen, whereas some later-drilled ones normally want a extra beneficiant remedy.
The goal is to offer all crops with the nitrogen required to provide an optimally sized cover. Trial work reveals that extreme early nitrogen can cut back yields considerably.
If the soil take a look at reveals excessive ranges of nitrogen, or if the biomass is excessive, the primary dose of fertiliser is adjusted in accordance.
The second utility is extra usually a flat charge of 90-100kg/ha.
Which means, a crop assessed to want 130kg/ha will get 40kg/ha in late February after which 90kg/ha in late March, whereas a crop needing 240kg/ha will obtain its first cut up of 150kg/ha after which the usual 90kg/ha later.
“It’s usually the early-drilled crops that are inclined to get much less nitrogen, whereas the later-sown ones want a bit additional to realize an optimum cover measurement,” he says.
Mr Batten straight manages in Hampshire, from north of Andover to Lymington on the south coast rising 544ha of oilseed rape throughout the two,700ha of land.
They drill from early August into the second week of September throughout a spread of soil varieties, so matching nitrogen charges to crop biomass is essential.
© MAG/David Jones
The primary evaluation of spring nitrogen requirement is made in January with a inexperienced space index (GAI) measurement.
On the finish of January, one block on the farm had a GAI of 1.8-1.9, and as one unit of GAI is equal to 50kg/ha, the crop would comprise almost 100kg/ha of nitrogen already.
The goal is to construct the cover measurement to GAI 3.5 by early flowering in April.
This index might be calculated by slicing all of the oilseed rape crop in a 1sq m patch, measuring the recent weight in kilograms and multiplying by 0.8.
As it is a prolonged course of, there are apps accessible that may assess GAI utilizing a cell phone.
The second evaluation is used to measure the quantity of nitrogen accessible within the soil. This may be performed with the CF N-Min take a look at, devised by CF Fertilisers.
The take a look at measures the quantity of nitrogen within the soil at the moment – the soil mineral nitrogen (SMN) – but additionally what’s going to change into accessible to the crop by nitrogen being mineralised within the soil – often called the extra accessible nitrogen (AAN).
This soil take a look at is carried out on the finish of winter earlier than nitrogen is utilized. The SMN and AAN values are added collectively to present a sign of how a lot nitrogen is offered within the soil.
The GAI measurement is used to calculate how a lot nitrogen is required to realize an optimum cover measurement.
Bagged nitrogen is utilized to make up the shortfall between the crop’s requirement and nitrogen equipped by the soil.
The soil mineral nitrogen testing on the farm is carried out by William Baldwin, operations director at soil sampling and trials group Envirofield.
He makes use of a buggy to cross every area to take soil samples right down to a 600mm depth, that are then despatched off to the laboratory for nitrogen testing.
The cost is £155/area, with at the very least 15 core samples taken throughout every area, and the outcomes can be again with the grower in about 10 days.
“The testing permits growers to handle nitrogen fertiliser charges to the crop’s necessities,” says Mr Baldwin, including that he’s seeing an uplift in enterprise this season pushed by the excessive price of nitrogen.
He suggests if growers use soil nitrogen mineral testing, they need to make use of a tramline trial to check the nitrogen charges prompt by the soil take a look at with regular farm apply to construct up confidence within the testing outcomes.
Again on the farm, Mr Batten makes use of the soil nitrogen testing throughout 5 fields of the 860ha farm at Norman Court docket, West Tytherley, so he can construct up an image of soil nitrogen provide throughout all of the land he farms and never have to check all of the fields.
Grain evaluation from wheat crops and the nitrogen content material of malting barley by way of the rotation give him added details about whether or not his nitrogen technique is suitable.
“We’re satisfied that it’s a small value to pay to reinforce our nitrogen suggestions,” he says.
With a light and dry winter this season, he’s hoping for a excessive stage of soil mineral nitrogen, which can assist him avoid wasting nitrogen prices this spring.
He believes testing works nicely and offers the group worth for cash, whether or not ammonium nitrate costs are nicely above £600/t or simply beneath £300/t like they had been again in June 2021.
The soil mineral nitrogen take a look at tells him how a lot N is offered within the soil, and he then seems on the relationship between nitrogen and grain/rapeseed costs to determine on an financial nitrogen charge.
Yield throughout all 588ha of oilseed rape on the Hampshire farms have averaged 3.75t/ha over the previous 5 12 months for regular double-zero varieties, and barely much less at 3.45t/ha for high-erucic acid rapeseed (Hear).
One added benefit of making use of the precise quantity of nitrogen the crop wants is extra even ripening, and the extra even oilseed rape crops have been simpler to reap, usually not utilizing glyphosate as a desiccant.
“Over the previous three years at Norman Court docket we’ve got not wanted to desiccate oilseed rape, as we’re rising extra even crops which makes harvest a lot simpler,” he says.
There has additionally been a dramatic decline within the quantity of lodging seen because the soil testing and variable nitrogen charges had been launched some six years in the past.
“It’s very uncommon that we see any lodging, and lodging may be very clearly linked to yield loss,” he says.
Managing the biomass of the crop may be very a lot about nitrogen, whereas the position of plant development regulators is to handle the crop peak and enhance the proportion of fertile tillers, he provides.
Velcourt has been utilizing soil nitrogen testing for quite a lot of years, however this season it’s extending the testing throughout the entire 56,000ha of farmland it manages, from Devon throughout to Kent and up the Moray Firth in Scotland, to have a look at fine-tuning its use of nitrogen fertiliser.
Nick Anderson, head of crop know-how, says grain nitrogen evaluation after harvest indicated important variability, with some farms not placing sufficient nitrogen on crops and others placing on an excessive amount of.
A deviation of 0.2% grain nitrogen from the optimum may point out misplaced yield potential of 0.5t/ha. In the meantime, excessive grain concentrations signify wasted assets and potential environmental prices.
“Diffuse nitrate air pollution and nitrous oxide emissions are issues that ought to concern all of us. It’s important we use all instruments accessible to us to optimise nitrogen charges,” he says.
Soil nitrogen assessments
- Soil mineral nitrogen (SMN) take a look at offers a snap shot of the available nitrogen within the soil
- CF Min-Take a look at offers a price for SMN plus an evaluation of soil mineralised nitrogen