Article taken from The Northern Farmer, December 2017, written by Wendy Short.
Chris Martin of Agrovista kicked off a series of autumn meetings with a review of the most recent oilseed rape season and an outline of the company's progress on its quest to maximise crop yields.
The 2016/17 oilseed rape growing season was described as a year of 'what could have been' by Mr Martin, who said that good establishment rates had been achieved under favourable conditions. Despite the long dry spell which followed, most Northern crops had rallied, with the exception of some localised problems with flea beetle and slug damage.
""On the whole, we enjoyed a decent autumn, with plenty of opportunities for spraying, so timings for light leaf spot and phoma sprays were not compromised. The mild temperatures encouraged vigorous growth and some of the larger canopies would probably have benefited from an application of plant growth regulator (PGR).
""Crops went into the winter in reasonable shape and the lack of frost meant they were very forward by the time spring arrived," said Mr Martin. 'Therefore, many growers missed timely herbicide applications. However, plants benefited from the dry April, which slowed down growth on even the thickest of crops. The dry, cool conditions also ensured a relatively low-risk sclerotinia year.
""Most oilseed rape was looking promising, but June was significantly hotter than usual, curtailing the time period for seed fill. We had few sunshine hours, heavy rain and strong winds, leading to localised lodging and a disaster for seed filling. Otherwise, we might have been looking at record-breaking crops.""
Several years' of research by Agrovista had confirmed that yield was determined primarily by maximising seed numbers, explained Mr Martin, with seed numbers largely determined by the level of photosynthesis in the two to three weeks after flowering. Meanwhile, photosynthesis for the remainder of the season was the main influence on seed size.
""Our work has shown that evenly established, low plant populations will give the most consistent yields and that precision drilling will produce a positive response, by allowing each plant to exploit the space around it and display its more natural prostrate growth habit. We have also found that seed per linear metre is more important than seed rate.
""Studies elsewhere have indicated that a key limiting factor to yield appears to be the minimum distance between plants in the row, and that a distance of less than 5cms will lead to strong competition and a subsequent yield penalty. For best results, I would advise limiting the number of plants per linear metre to no more than 15.
""Field management is also important and encouraging unrestricted root growth should be one of the main priorities, including the alleviation of compaction. Close attention should be paid to ensuring that seedbed nitrogen and phosphate are adequate, as these nutrients will provide the roots with energy they need to grow and search for nutrients in the soil. Another essential is adequate consolidation, to encourage good seed to soil contact.""
Effective early weed control was another way to ensure a good harvest year, added Mr Martin, and this was particularly important when lower seed rates and/or wider row spacings had been adopted. Lush crops in early autumn should receive a PGR, as well as an autumn phoma and light leaf spot treatment.
Trial crops had also shown that yield potential could be improved through an autumn application of the amino acid product, Terra Sorb.
He advised growers to establish targets for the green area index (GAI) of the crop as the season 2018 progresses.
""At mid-flowering, the aim should be for plants with healthy leaves and a crop with GAI of 3.5 - 4.0," said Mr Martin. ""A useful method of monitoring progress is to look down into the canopy from above, where about five to ten per cent of the soil should ideally be visible.""