How dry is your soil after planting?

Do you know what to do about it to avoid 'Scab'?

This is on a site in North Lincolnshire recently. Watering with a can appeared to wet the soil well, but monitoring with the Diviner in the field quickly showed that a very large amount of water was needed - subsequent use of the spade soon showed that what the Diviner was saying was true - the water had not gone below the top 10cm, even though over 30mm of water was applied. The likely deficit from cultivation, de-clodding and planting was in the region of 50-70mm!!

There are a number of questions the grower needed to answer:

How dry is my soil?

How much water do I need to apply to wet it fully for scab control?

How do I get it wet enough for good 'scab' control?

With most water monitoring systems it is important to know when a soil is 'full'. We see many fields that have poor soil structure due to the de-clodding and planting activities. This, we believe helps cause 'scab' in soils that in some years have no problem, as well as poor growth early in the season. The 'normal' practice is for growers to go over their crop with 15mms of irrigation to overcome these difficulties. Since we have been involved with the EnviroSCAN we have been able to 'see' how much water it takes to refill a soil, but many growers who do not have the luxury of such equipment do not know how much water is needed. (In 1996, after a dry winter many soils needed 70mms to refill the soil to 50cms. Not many growers were able to achieve this and hence had disappointing crops. If you 'guesstimated a 30mm deficit, you would have been 40mms out for the season!).

Recently we conducted an experiment in filling a heavy soil after planting potatoes. Access tubes were installed in a field and using our new Portable 'EnviroSCAN' probe, called the Diviner, we were able to take readings, then water the tube with a watering can and take more readings. The agronomist who did the work was 'amazed' at how long it took and how much water was needed. You can see below the figures that show our conclusions. Our conclusions are that it took 1.5 hours to refill the soil and it needed 42mm of water! No wonder the 'average' grower does not refill his soil and hence has poor crops. (Probably much more water was needed to achieve this.)

You do need good equipment that is agronomically correct to be able to see this. The EnviroSCAN has always done this, but the new Portable Diviner, used sensibly, does it admirably.