Dry and warm winters are more important to achieving high yielding crops than warm sunny summers, according to data from the Yield Enhancement Network (YEN).

ADAS Head of Agronomics, Daniel Kindred, has been studying the data from over 1600 crops in the UK and northern Europe and has found stronger correlations between winter growing conditions than summer.

He said: “It was a surprise that we didn’t find a strong relationship between the rainfall and sunshine in June and July with yields. We don’t necessarily see high levels of sunshine in June and July with corresponding high yields in the dataset. What is coming through more strongly in the dataset is the weather in winter.”

The data shows that that mild and dry winters are associated with higher yielding crops of wheat and barley. Dr Kindred points out that conditions at this point are critical to crop establishment, and achieving good rooting. Conversely the conditions in summer did not show as close a relationship with eventual crop yield, despite the fact that we know sunlight and access to water in summer are critical to crop growth and yields. From the data conditions over winter seem more important than conditions over summer.

It is important to note that whilst the dry winters are good there is usually always enough rainfall everywhere in the UK to fully re-wet the soil from the previous summer. Wetter winters can cause prolonged waterlogging and hamper root growth.

Another surprise in the data was that the researchers haven’t found a relationship between organic matter in the soil and yield. This is despite knowing how critical soil organic matter is for soil health and its assumed benefits for moisture retention and nutrient availability.

“It was another surprise that soils with higher organic matter were not performing better than lower content soils,” explained Dr Kindred. “This is a large and growing data set and we may find relationships if we drill down into specific contexts, when we drill down to smaller locations but across the wider piece we couldn’t see a clear connection. However we have seen a benefit from manure use in the dataset.”

Access to water for the plant was found to be one of the key factors though, as shallow soils or those with high levels of sand or gravel consistently performed poorly. He said: “There is a lot of talk about the top six inches being vital for glad growth, which they are. But when it comes to water, it is extracted from the top two metres. The soil and ground for over six feet under the crop plays an important role in watering the plant.”

The data set has shown second wheats to lose around 1t/h compared to first crops, but there was not much difference between break crops.

According to Dr Kindred, Scotland is potentially in a sweet spot. The data is showing increasing yield with increasing latitude, despite the lower solar radiation levels. This may be because sunshine is spread over more hours than further south with lower peak intensities. This means that the plant can better make use of the energy of the sun because it is not too bright and the days are longer.

It seems that there is a ‘farm factor’ at play, as the variation in yields can’t all be ascribed to differences in soil, weather or agronomy, but there are consistent differences between fields. This may highlight the importance of ‘attention to detail’ with getting the whole system right from soil management, to variety choice, nutrition and protection high. However Mr Kindred was keen to point out that there were no silver bullets to achieving successful yields. Scottish cereal growers could be aiming for 6t/acre wheat according to Dr Kindred.

“From the data we can not see why other farms shouldn’t be aiming for really high yields,” explained Dr Kindred. “There is nothing we can see theoretically why we shouldn’t be able to achieve yields close to 15t/hectare for most farms which can provide enough water to the plant. Sandy, gravel or shallow soils will be more limited in yield.”

Dr Kindred’s investigations into the YEN data have so far been very preliminary. The YEN only exists due to the generosity of its sponsors, but this only gets us to the point of collecting and reporting the data for each season. There is a massive opportunity to learn more from the dataset and ask and answer the questions that matter to farmers, but this needs more resource. If funding becomes available then research could look at understanding the causes of the 6-16 t/ha variation in grain yields. Other projects could look at working out ‘what works’ in achieving better yields, performance and financial returns, surely must be a high priority for the industry and for Government.

More details at at www.yen.adas.co.uk