Archive Article: 1997/10/18
Whats the best crop to follow late harvested roots?
Wheat, according to Ben Freer, agronomist with Morley Research Centre. Last autumn his answer would have included barley, because malting prospects looked rosy and premiums were high.
"This year the comparative returns on wheat are much better in spite of the fall in the grain market. On the farm here at Otley, Suffolk, November-drilled spring and winter barleys on our heavy clay site gave about 7.4t/ha. We are waiting for the nitrogen results on these but were not optimistic about receiving much in the way of premiums."
However, Charger winter wheat sown at the end of September managed 9.5t/ha (3.8t/acre). A direct comparison with November-drilled Charger cant be made at this site, but at the sandy loam trial at Morley, Norfolk, Charger topped the league of late-sown wheats, with 9.2t/ha (3.7t/acre).
Mr Freer acknowledges that this trial yield would not be repeated in a farm situation but still reckons that on balance the greater tonnage performance from November-sown winter wheat would outshine barley on the better soil.
This advice may not hold true for every situation, he warns. "Its not always possible to make a seedbed in November if beet comes out in excessively wet conditions leaving ruts. In this case, wait until the soil is fit and then drill spring barley – as long as your soil isnt too heavy."
What yield loss on wheat might be expected as drilling date is pushed back?
In normal conditions Mr Freer would expect to lose 2 to 2.5t/ha (0.8-1t/acre) from a potential 10t/ha (4t/acre) wheat crop, if sown after beet in November-December at the Otley heavy land site.
Delaying drilling costs more on lighter land than on heavier soils. Pushing forward drilling by two weeks in September on light land can add 1t/ha (0.4t/acre) to yield.
On medium soils yields fall off most rapidly in October, losing 1t/ha (0.4t/acre) from the start to the end of the month. On heavy land, yield potential is more robust – the tail-off during November is less, but the risks are greater of bad weather stopping drilling.
Much potential yield loss depends on soil conditions – in particular, moisture. Last year seedbed conditions were dry, exacerbated by the removal of moisture by the beet. This can upset establishment and reduce yield potential.
As December approaches, the arguments increase in favour of spring, rather than winter crops. But Mr Freer favours staying with winter wheat as late as possible. "If soil conditions are right. Theres more yield and profit potential in wheat," he adds.
So wheat is the favourite -but which variety most suits late drillings?
Choosing the right variety can help limit the profit loss from late drilling, says Mr Freer. This years late-sown wheat results from NIAB (see fig 1) show a big difference of 1t/ha (0.4t/acre) between best and worst performers.
These results dont tally well with the five-year average scores, probably due to dry establishment last autumn. First, yields of late sown wheat trials are down by about 0.8t/ha (0.32t/acre) from last year. Second, the running order has changed, with Cadenza returning to the top of the list after some time in the doldrums. And Brigadiers performance is well down.
But perhaps the 1997 results could be more relevant than the five-year average this season, because drilling has got off to another dry start. One variety to note is Charger, believes Mr Freer. "As a late-sown wheat, Charger looks particularly good. Lodging affected some crops of Charger this year – and sowing later will reduce the risk."
As drilling date moves on, varieties such as Chablis and Shiraz become more interesting. "These can be safely drilled through until spring," he comments. "With Shiraz, there are also premium marketing contracts available."
With a bumper beet crop expected, should I lift beet earlier and drill earlier?
At first glance, this strategy looks tempting. Many growers expect to fulfil quota easily from this years crops. So extra beet would only receive C prices. Thus an early lift, then clamping to store until the delivery date arrives, might make sense.
The argument is that at C prices, the resulting crop loss would be less significant, and earlier drilled cereals would yield more.
But a look at the figures shows this would be a mistake, says Dr Keith Jaggard of IACR-Brooms Barn. "Its not worthwhile – even in a year like this." Two factors to consider when weighing up the costs of lifting earlier than needed; the loss of sugar due to crop growth interruption, and loss of sugar in the clamp.
First, the interruption to growth. Gains in sugar yield can be significant during October through to November (see fig 2). Even at C beet prices, this sugar is worth having.
Translated into root yield (adjusted to 16% sugar), and taking the C beet price as £12/t, it would add £3/ha to returns for each days growth in October. For the first two weeks in November, sugar yield increase is not as fast, but the crop will still put on £1.50 worth of C beet/ha/day.
In late November, growth is slower, though much dependent on weather conditions. On average growers could expect about 50p worth of C beet/ha/day.
Second, clamping losses. Even the most well-managed clamps will see some deterioration, due to respiration, says Dr Jaggard. And this is mainly dependent on temperature. The higher the temperatures, the faster the root respiration rate.
Adding growth loss and clamping deterioration, it is calculated that growers could lose C sugar worth £176/ha (£71/acre), by lifting in October and storing until December.
It would be difficult to re-coup this loss from an earlier drilled cereal, concludes Mr Freer. "Youd be unlikely to hit the top wheat yield potential. But this strategy could perhaps be worthwhile later in the season, at the end of October. Then lifting and clamping for a few weeks might be a way of drilling wheat in October instead of November."