NIAB - National Institute of Agricultural Botany

Orson's Oracle

The value of a day’s delay

Posted on 02/10/2015 by Jim Orson

We got up at 2:30 a.m. the other day to view the eclipse of the super moon. The fact that we had a good view of the event meant that the sky was clear. The weather was set fair and so I knew that cereal drilling would soon be going ahead at a frantic pace.

Do not take this wrongly but I was hoping for another few days of delay in drilling winter wheat. Wet weather delayed drilling until about 10th October in 2009 and ensured high levels of black-grass emergence prior to that date. This was also the first autumn of the wider adoption of stacking of the pre-emergence herbicides. The resulting black-grass control was generally more than satisfactory. The level of control was attributed by many to the stacking of the pre-emergence herbicides but the involuntary adoption of the cultural control measure of delayed drilling also played a significant role.

After a wet spell there is always the temptation to get on the land and drill before it is really suitable. The most extreme case was in the autumn of 2000 when it seemed to rain almost every day. Surveys of NIAB TAG members clearly showed that those who puddled-in wheat that autumn had inferior yields to those who waited for the better soil conditions in the first couple of months of 2001.

What has always amazed me is the rate of reduction in soil moisture below a depth of 30cm. One day the spade would tell me it was too wet to cultivate but the next day it seemed dry enough to cultivate. Salle Farms in Norfolk, which keeps meticulous records, have shown that for a few days yields increase with every day’s delay in drilling after a sodden soil starts to dry.

Now, there is data to demonstrate the impact of leaving the soil just another day (see the diagram) or preferably two days before wheeled or tracked vehicles run over it. This data was collected by the University of East Anglia as part of their government funded research project, the Demonstration Test Catchment study of the River Wensum in Norfolk. It shows the rapid drying of the medium textured soil at 30-50 cm depth between 5th February and 6th or 7th February 2013 despite little change in the moisture status of the shallower layers. As farm equipment has got heavier over the years this information takes on added significance in trying to avoid compaction in the deeper layers of the soil.

The take home message is quite obvious, do not rush back onto the land as it starts to dry after it was sodden. A day or two’s delay may be handsomely rewarded in terms of crop yield. Regular use of a spade will only confirm the message and improve decision making. So keep digging.

 

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