Seeing is believing?

29 Oct 2013

It’s always been said that many farmers adopt or adapt techniques by ‘looking over the hedge’ at their neighbours. Nowadays ‘looking over the hedge’ should not be taken too literally as it is a process that includes all forms of communication. However, seeing should not always necessarily mean believing.

I don’t think we’ll ever regain the world wheat record from New Zealand now that they’ve really got their act together. In this context, this year’s UK record wheat crop was a real achievement. NIAB TAG’s monitoring of weather variables suggested that the area where the UK record crop was grown was favourably treated by nature this spring; higher than average levels of solar radiation and sufficient rainfall were recorded.   

Much is being made of the level of foliar nutrition that was received by the wheat crop that broke the UK wheat record. There’s the assumption that this significantly contributed to the high yields and it appears that the farmer, whose attention to detail is impressive, is convinced of this.

Now, I don’t want to be a killjoy but I’m not quite so convinced. Perhaps this is inevitable from a boring science-based agronomist whose views have been coloured by similar (and eventually proven to be unsubstantiated) claims throughout his career. Perhaps this time it is different but I should like it to be validated in field trials where yields with and without the foliar nutrition are compared.

What was different about the approach to the record UK wheat record crop is that the farmer applied foliar nutrition from early post-emergence onwards. I don’t think that’s been assessed experimentally in the past. Usually these products have been tested in single applications rather than in a multi-application, multi-year approach. The farmer’s high yields suggest that this approach needs to be evaluated experimentally.

There are yield benefits from splitting the total season-long dose of ‘bag’ nitrogen. In trials in years gone by, there were yield benefits from increasing the number of spring nitrogen applications. The biggest yield benefit was going from one application to two. The yield benefit got progressively less with each additional application. The current standard of three applications is a pragmatic approach bearing in mind labour and machinery costs but there would be yield benefits from having one or two additional applications. However, it must be remembered that we farm to optimise margins and not to maximise yields.Wheat

In press reports, the farmer who grew the UK record crop laments the fact that he cannot use, for environmental reasons, the very high dose of applied nitrogen that was used to grow the world record crop of 15.64 t/ha in New Zealand. He is reported to have used 220 kg N/ha. In fact he may not have had to use much or any more because Eric Watson, who also farms in South Island New Zealand, has achieved a field yield slightly higher than the world record with around 250 kg/ha of applied nitrogen. The level of soil mineral nitrogen in this case was 100 kg/ha. 

In NIAB TAG trials the optimum applied nitrogen dose is not reduced by this level of soil mineral nitrogen. To reinforce this point, Craige MacKenzie, who farms a few miles from Eric Watson has also achieved a field yield higher than the world record from a total of 262 kg/ha of applied nitrogen where the soil mineral nitrogen was 35 kg/ha. Unlike Mike Solari, the world record holder, both Eric and Craige have the benefit of variable rate irrigation.

This suggests that, while the amount of nitrogen that a crop can access may limit yield, very high wheat yields can be achieved by not exceptionally high doses of applied nitrogen. What is essential is the correct crop structure, prolonged ripening with high levels of sunlight and an ample supply of moisture. The final and critical element must be the skill of the farmer with particular emphasis on attention to detail. I remember vividly having a prolonged discussion with Mike Solari about seed rates and tiller numbers and what constitutes a ‘too thick’ crop. 

As an aside, one intriguing observation can be made when looking at the results of UK trials on trace elements and/or plant vigour sprays. Usually these trials have two control treatments. One control treatment is standard crop management and the other is the same but receiving a spray of just water applied at the same timing and volume of application as that used for the trace element and/or plant vigour sprays. It’s not unusual to see a yield benefit from all the spray treatments, with or without the trace element and/or plant vigour products. I’ve often pondered why such a small amount of applied water can make such a difference.