Fertilising oilseed rape while sowing is becoming popular. Andrew Blake finds out why.
For farmers with memories of ancient combination drills which applied seed and fertiliser together, the recent trend for placing fertiliser in narrow bands when sowing oilseed rape may seem like reinventing the wheel. But the technique, which some estimates suggest could account for up to 40% of the 2011-12 crop, offers several benefits.
The key advantage is that it allows growers to meet NVZ rules, which restrict autumn nitrogen applications after 1 September to 30kg/ha, without compromising crop performance, explains Yara’s Mark Tucker.
Although the firm’s trials, which began in 2009 using the Chafer Quickstart approach, have shown no practically achievable yield increases, crop establishment has been improved and so cuts in spring N applications should be possible, he notes.
“The yield benefits, compared with broadcasting the same amount of fertiliser, have ranged from 0.1t/ha to 0.38t/ha,” says Mr Tucker. However only the latter, which involved 100kg/ha of banded N (equivalent to an impractical 300kg/ha overall) was significant, he stresses.
“But there have been definite increases in biomass likely to reduce the rates of spring top dressings needed, and we’re still trying to determine by just how much.”
In last season’s work, the optimum autumn N rate for the crop was an NVZ-busting 66kg/ha, he adds. “That clearly justifies banding which allows you to keep within the limit.
“Another benefit is that you aren’t feeding the weeds between the rows.”
Masstock’s work with an alternative banding technique, via a Simba 300DTX and Opico HE-VA machines, has been more encouraging with average yield increases of 0.5-0.7t/ha in trials at Brotherton, Yorkshire, according to the firm’s Philip Marr.
“I think probably 40% of OSR growers will be using something like this this autumn.”
Adequate seed-bed nutrition is essential for good oilseed rape establishment, notes Mr Marr. “In the early days, with single-low varieties like Jet Neuf and Bienvenu, we combined drilled 15:15:15 fertiliser at 100kg/ha. Although the following double-lows probably needed more help with nutrition because of their less vigorous nature, the time-consuming task of refilling the fertiliser hopper meant that operation was dropped.”
However, the move to establishing crops via subsoilers has seen the idea of fertilising during sowing revived, he says.
“It’s important to ensure the seed is adequately covered by soil and that the fertiliser, applied in 4-6 inch bands either in front or behind the seed delivery pipe, is mixed well with the soil to make the nutrients available to the primary root system.
“I’ve found the optimum N requirement is around 25kg/ha within the band (about 75kg/ha overall) – the crop doesn’t respond to more. Soil analysis should determine whether phosphate and/or potash needs to be added.”
Agronomist Chris Rigley of Yorks-based Crop Nutrition Initiatives believes more growers must treat oilseed rape as a crop in its own right rather than as a mere cereal break.
“For the past 4-5 years, people have been thinking more seriously about it as they try to ramp up yields and move away from poor establishment techniques such as auto-casting.
“The first 40-45 days are critical in its life and the challenge is getting the nutrition right then. You can’t do that with foliar sprays at that stage.”
Rather than pursue the subsoiler/cultivator banding approach, CNI has developed an applicator, the “Nutri-Feeder”, which Mr Rigley says can be retro-fitted to most seed drills. “It’s now in its second season and I have it on two Horsch drilling units.”
It allows liquid nutrients, as yet only NPK solutions plus crop and soil-specific micro-nutrients, to be injected directly onto the seed as it goes into the ground, he explains. “What doesn’t adhere to the seed goes into soil surrounding it, providing a nutrient-rich environment.
“This nutritional package, in liquid solution is immediately available to the growing seed,” he adds. “Solid materials do not provide this advantage.”
Already used on cereals, the new applicator has created N savings of up to 20kg/ha with no yield loss, he says.
Working with Peterborough-based Safagrow and other leading nutrient manufacturers, Mr Rigley plans to trial a range of products which can be tank-mixed with the standard 100litre/ha NPK application to supply other nutrients, such as sulphur, magnesium, boron and molybdenum.
Evidence is growing that the high rates of sulphur that some oilseed growers are applying may be leading to molybdenum deficiencies, notes Mr Tucker.
Safagrow specialises in producing suspension concentrates (SCs), notes the firm’s Andrew Low. Although the products will not be commercially available this autumn, SCs offer two key advantages, he explains.
“They allow for significant amounts of all nutrients to be applied in relatively small quantities of final product. And due to the slow solubility of such formulations, they will remain in the soil profile at seed level.
“Our current thinking is that we should be able to provide sufficient nutrition with an application of only an extra 10 litres/ha.”
The same products will also be suitable for foliar application later in the season, he notes.
So-called till-feeding of oilseed rape is catching on fast, agrees Andy Eccles of Omex. “I reckon it’s up to 40% of the crop in some areas, but nationally it’s probably only 20-30%.”
The firm offers several liquid nitrogen/phosphate mixtures, including TPA, an additive to prevent the phosphate becoming “locked up” in the soil. “In my view they really need to be applied in a 5cm band after the tines or drill coulters. Putting them on ahead isn’t a good idea because they can be moved away from the seed as the soil gets disturbed.” Ideally they should be dribbled or streamed on – small droplets in sprays can lead to drift, he adds.
The idea of sowing seed mixed with suspension fertilisers lost favour, he admits. “Once the seed was mixed in the fertiliser it triggered germination which was not supported in dry conditions.”
Case study: Daniel King, Lincolnshire
One grower pleased with the results of fertiliser placement at drilling is Daniel King, based in Lincolnshire.
“I wasn’t happy with our yields under a conventional establishment regime, but it was clear that more fertiliser wasn’t the answer,” he says. “We were putting on what the crop required, but it wasn’t getting to where it was needed during germination and root development.”
Consultation with Chafer Machinery saw Mr King’s idea of placing Omex fertiliser alongside the seed and sowing in bands rather than rows eventually developed as the Quickstart system.
Putting nutrients directly where the plants need them means they are accurately placed, immediately accessible, and has cut establishment fertiliser costs by three-quarters, he says.
“This year’s crops, sown with the Quickstart mounted on our 3m Vaderstad TopDown – equipped with Simba SL legs to minimise disturbance – emerged very evenly, even under trees and on the headlands.
“The system has also helped our weed control. We’re under massive pressure with blackgrass, and the stronger rape growth has helped with control.”
The farm’s five-year yield average is 3.4t/ha. “My target now, with Quickstart having proved itself, is for a more consistent 4.3-5.0t/ha.”