10 May 1996

How irrigation planning will pay dividends

WITH water likely to be at a premium for irrigators this season, assessing need and scheduling applications correctly could reap higher rewards than usual.

Ground cover, and the speed at which crops reach full cover, could have a huge influence on the outcome of irrigation programmes, Eric Allen, director of Cambridge University Farm told a PMB conference at Keele University.

"The first thing to determine is what is complete ground cover," he said. "Differences are crucial." Most crops in 1994 and 1995 had reached full cover by the end of May. Few were likely to do so this season.

Errors at the outset could only accumulate, he warned. Assessing crops from a vehicle on one side of a field only could be very misleading.

Compaction was another under-estimated constraint, he maintained. Compacted soil restricted rooting depth, reducing the capacity of crops to absorb applied water.

Varieties differed a lot in their rooting depth, added Mr Allen. "You must take that into account in determining how much water a variety can take out of the soil."

Whatever scheduling system was used the key was to establish applications were really needed, he stressed. "A great deal of water can go on to produce no yield." It was irresponsible and wrong to use irrigation in the belief that it would intrinsically boost yield.

Scab control could merit more frequent applications. But often too little thought was given to matching the planting of sensitive varieties like Maris Piper to the available equipment, claimed Mr Allen.

"A little thought in that direction could produce huge dividends for many growers."