Let light put shine on yield
WINTER oilseed rape crops are often too thick. By thinning them out in spring yields could benefit considerably, according to new research at the University of Nottingham.
"Growers kept telling us that thick crops dont always do as well as expected and that backward, sparse ones can give quite high yields," said Dr David Stokes at last weeks AICC conference in Buxton.
Outlining the first year of HGCA- & MAFF-funded experiments he said results were quite encouraging, giving up to 0.6t/ha (5 cwt/acre) extra yield.
Work in the 1980s found that the number of pods/sq m is a key component of yield. But unless enough light gets to all the pods and nearby leaves, many abort and much seed fails to develop.
In one typical finding a thick crop of Capricorn grew an average of 6500 pods/sq m. A thinner one produced only 5000 pods/sq m. But the latter had an average of 21 seeds a pod compared with only 15 in the thicker crop.
The thin crop gave 4.91t/ha (40cwt/acre), but the thick one only 4.32t/ha (35cwt/acre).
Dr Stokes acknowledged that in practice the risk of poor autumn establishment and threats from pigeons and slugs ruled out an ultra-low seed rate approach to cash in on the findings.
However, latest trials at Sutton Bonnington using nitrogen fertiliser to manipulate spring canopy size have proved promising. At ADAS Rosemaund tests of various seed rates, sowing dates and mowing the crop are also encouraging (see table). "The results are in line with what we thought. But we have a long way to go before we can put the theory fully into practice.
"What we need to do is to get the crop going well over winter. But we then need some understanding of whether it is too forward or too backward – thats still subjective."
Ideally there should be some specific targets for growers to aim at. It might even be feasible to thin the crop mechanically, said Dr Stokes. Grazing with sheep was probably unsuitable with current varieties.n
• Often too thick.
• Poor use of sunlight.
• Results in: pod abortion seed loss.
• V low seed rates ruled out.
• Spring management may be key.
• N & mowing under trial.
Oilseed rape yields in ADAS Rosemaund trial – t/ha
unmownmown in Jan
Early sown (early Sep)High (120 seeds/sq m)4.034.35
Low (60 " " )4.374.46
Late sown (late Sep)High (120 " " )4.084.10
Low (60 " " )4.504.25
Propham withdrawal prompts
thin end of wedge concerns
SUGAR beet growers on organic soils are among the first broad-acre producers to be hit by manufacturers decisions to withdraw support for a specific herbicide.
As of April 9, 1997 approval for pesticides containing propham will be revoked. As normal in such cases, existing product supplies may still be used legally over the next two years.
The move comes after no firm was prepared to provide the data package needed to get propham included on the ECs Annex 1 list of active ingredients. There was little economic justification for doing so for a material used on such a small scale, explains Chris Delf of Atlas Crop Protection.
Withdrawal of approval will inevitably reduce the herbicide weaponry for some growers, he says. "We are working to get sugar beet onto the Atlas CIPC 40EC label, which should be a crumb of comfort to those on the blacklands who are traditional users of propham."
Chloridazon is the most cost-effective alternative, albeit not quite so effective, according to Simon Fisher, British Sugars technical services manager. Only 5-8% of the UK crop is grown on mainly organic land, he points out.
Chris Wise, pesticides specialist at the NFU, says prophams disappearance mirrors events which have seen several products for minor horticultural crops go the same way. "Its the thin end of the European wedge. Our view is that it could be the first of many for growers."
Recent meetings with EC officials however have been encouraging, says Dr Wise who chairs the phytosanitary group of COPA. "Its nice to say that weve got the commission sitting down and beginning to appreciate growers problems."
There is little the NFU can do to offset the harshness of such commercial decisions. But "mutual recognition" of Annex 1 materials offers some hope for the future of off-label uses on minor crops, he says.n
Affected propham products
Atlas Gold; Atlas Indigo; Atlas Pink C; Atlas Electrum; Luxan Gro-Stop; MSS Sugar Beet Herbicide; Sugar Beet Herbicide (United Phosphorus).
A lot less flush to avoid crisis
RESTRICTIONS on the use of water for crop irrigation could be eased or removed if the volume of water used each time a toilet is flushed were reduced under new water conservation measures.
The Country Landowners Association says preliminary findings of a Department of the Environment study to avert a future water crisis shows too much water is being flushed down the nations loos.
A reduction of one-third in the volume of water used each time a toilet is flushed could result in a 10% saving in national water consumption, says Ian Kibble, the CLAs Yorkshire regional secretary.
Water is a vital resource for food production, Mr Kibble adds. As such agricultural use needs addressing in any study of water resources and supply.
• More on water usage – p66.n