Spring Drought

  • Written by Andrew Davis
  • Posted on May 26, 2017
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The rain a fortnight ago was urgently needed following months of below average rainfall. In this area, at least, it was the right sort of rain, gentle and continuous all day, although other parts of the country had heavier storms, much of which ran off the parched earth. But was it enough and in time to save this year’s harvest?

Much of the winter barley grown today is of 6-row hybrid varieties. These seem quite resistant to drought and have thus coped reasonably well. Winter oilseed rape, too, seems to have survived the drought but may have been damaged by the frosts in late April. That will only become clear when the seed pods fill and we see whether the cold night temperatures affected flowering. Both winter and spring beans seem in relatively good shape, now growing away after a good watering.

The main impact of the drought followed by the rain is an interesting one. All organisms have defence mechanisms to cope with stress, reproducing a soon as conditions allow. Thus many plants will react in such circumstances by throwing up a seed head, including members of the Graminaea family. Many crops of winter wheat were suffering from lack of moisture and short of nutrients particularly nitrate, shedding tillers. Cereals produce tillers or side shoots which results in more ears but not necessarily higher yield. If there are too many tillers, there are fewer grains per ear and they may be small. Too few tillers may result in the remaining ears having more, larger grains but this may not compensate for fewer seed heads.

To lose tillers in the spring is likely to have a detrimental impact on yield, but that is less critical than the premature seed heads. Most wheat varieties come into full ear around the middle of June, although Skyfall, a very popular variety at present, is earlier than most. That then gives six to eight weeks for flowering, grain fill and ripening before harvest in mid-August.

This year many crops starting coming into ear in mid-May and are now about to flower, even though many of the plants are barely above knee height. The lack of leaf area could be critical when it comes to grain fill, limiting the amount of solar energy absorbed. Some farmers decided not to use growth regulators this spring because of the lack of growth, a decision that may prove inspired. Many crops have a distinct blue tinge, a sign of excessive waxing of the leaves in an attempt to prevent moisture loss.

Now that crops are growing again, it is important to keep them green as long as possible by applying nitrate fertilizer and fungicides to prevent disease. What is not clear, however, is whether that would be throwing good money after bad if the damage has already been done. There is little disease pressure at present anyway with the exception of yellow rust in susceptible wheat varieties, although a period of warm damp weather would see pressure increase, particularly from mildew. Orange blossom midge may become a problem in those varieties not resistant as there is little chemical control.

Some spring sown crops have barely established and have a lot of growth to catch up. This is certainly the case with maize grown for silage, much of which has only emerged since the rain. My neighbouring dairy farm may well have to cut its winter wheat for whole crop silage to compensate for lack of maize growth.

Those who took first cut silage before the rain are now benefitting from rapid regrowth whilst those that did not have been harvesting in the dry weather, trying to get the silage made before the rapid production of seed heads reduces the quality.

However much the drought may have been the major limiting factor for most farmers this spring, for others, particularly fruit growers, the hard late frosts have been even more critical. English vineyards are suggesting that losses may be 50%, a massive blow for those who have recently invested heavily in the rapidly expanding English wine industry. There was the amazing sight of bonfires lit in vineyards in an attempt to stave off the frost. The news from France seems little better but cynics suggest that may just be an excuse to raise prices even higher. Fruit, too, such as apples and pears, must also have suffered severely.

As ever, much will depend upon the weather between now and harvest. Further prolonged hot dry weather could be disastrous leading to a very early harvest. Taking the six to eight weeks rule of thumb from ear emergence to harvest, winter barley may be cut by the end of June and even winter wheat by the end of July. Nature has an amazing capacity to recover from adverse conditions but there is a sense of dread amongst the pessimists at present. Farmers are a resilient breed; they need to be to cope with the factors outside their control, notably the vagaries of the British weather.