Shape of the soil remains a critical factor

Article taken from the Northern Farmer, written by Wendy Short

Oilseed rape prices have been disappointing, but the market has marginally improved, thanks to a weaker Euro.

It is still a popular option with growers, however, largely due to its benefits as a break crop.  Agrovista has been researching the options for establishing the crop and the company’s Chris Martin explains the findings to date, as well as giving updates on unmanned aerial systems (UAS) and blackgrass control.

Several years of testing various machine combinations across a wide range of UK soils suggest that a one-pass machine is ideal for most situations, mainly because rapid seedbed preparation helps to preserve soil moisture levels, said Mr Martin.  If the crop follows winter barley, then light cultivation and consolidation will stimulate weed growth, which can then be sprayed off using glyphosate before drilling.

When it comes to assessing soil structure and compaction damage, in order to make repairs, technological advancements cannot replace the spade, he stressed.

“There is no substitute for manually digging holes in several areas of the field and measuring the depths of compaction,” he says.  “This will ensure that any steps taken to improve the soil structure ahead of sowing will be carried out effectively.

“The working depth and type of leg required will depend on the individual situation, but it is important to only go as deep as necessary and certainly no more than 2cm below the compaction layer.  More damage is done by sub-soilers being set too deep than is ever corrected.”

The equipment should also be capable of applying solid or liquid nitrogen and phosphate.  For optimum results, fertiliser should be placed in two positions, to create a grow-bag scenario for the developing seedling.  Placings should be one band just below seeding depth, with one to the side, or slightly higher.

Applying the seedbed fertiliser in more than one position will help to avoid lazy rooting, he said.  Following behind the leg, a light cultivation will usually be required.  This will provide tilth and help to incorporate any straw or chemical residue into the soil.  After this stage, the seedbed should be consolidated.  This is best achieved through the use of a press wheel.

The coulter system adopted for oilseed rape should be capable of placing the seed with even spacings, research has shown.  It is also important that the seed is placed at a uniform depth; this should be no greater than 25-30mm.

Company trials have revealed no discernible difference between row spacings of 125-550mm, as long as the seed spacings between the rows have been set correctly, added Mr Martin.  The first point of competition within the rape crop will usually occur in the row of sowing; a gap of less than 5cms between seeds will bring in too much early competition and ultimately reduce yield.

“There may be advantages to be gained by making wide rows – ideally at 300-400mm apart – because this allows inputs to be targeted with greater accuracy,” he says.  “This type of system also permits the seed to be placed directly in line with the legs which loosen the soil.

“Another requirement for good oilseed rape establishment is a press wheel, which will encourage sufficient seed-to-soil contact and act as a deterrent to slugs.  After sowing, the field should be rolled, if conditions allow.  Some soils will remain cloddy after one treatment and double rolling may help to break the seedbed down further.”

UAS Trials

Agrovista has been evaluating the use of UAS technology to track crop weed infestation.  It uses an aerial, computer-controlled machine to travel over plants at key points in the season.  The machine gathers images, which are run through a software program, to analyse weed species and levels.  Early indications from the herbicide USA pilot project are promising.  They have shown that UAS results for blackgrass, for example, closely match the weed counts carried out using traditional methods.

Blackgrass Control – Water Volumes

Agrovista field officers have trialled several different water volumes, for use with pre-emergence herbicides for the control of blackgrass.  It has been concluded that higher water volumes produce the best results.

For post-emergence contact graminicides, the most favour able effect came from using spray nozzles to give finer droplets, although work is still be done on methods to reduce the higher risk of drift that accompanies finer droplet spraying.

Mr Martin issued a word of warning.

“Drift control agents do not fall into a category in which formal evaluation is necessary and therefore it is possible that claims by the manufacturers may be inaccurate.

“It is advisable to look for products that are accompanied by biological data, as these will be the most likely to live up to the makers’ claims.”


10 April 2015

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