17 July 1998

N no longer likely to help tardy beet crops

SUGAR beet growers whose late sown crops are suffering should make sure soil structure is not to blame before applying more nutrients.

Fertilising with nitrogen now is unlikely to help overcome compaction and could cut sugar contents and increase impurities. Only in exceptional cases can more N be justified, and only then in small amounts, say specialists.

The 85% of the crop drilled before Aprils downpours is very promising, says British Sugars northern area factory agricultural manager, David Dunning. But the late-sown remainder is causing some concern.

"What we are seeing is soil management difficulties coming to the fore," says Mr Dunning. "Most of the problems are tied in with soil structure and poor rooting rather than soil nitrogen."

On some fields manganese deficiency may merit correcting, and fast-acting lime could usefully be used to boost some crops, he suggests. "We are seeing many more acid patches this year." But on the whole extra nitrogen now is unlikely to help, he maintains. "It may feed the eye but not the pocket."

BSs Ipswich-based Richard Cogman, who has relatively few backward crops in his area, agrees. "We certainly would not advocate nitrogen now unless you are sure you have a deficiency." Trials with foliar urea in the late 1980s and early 1990s proved the point, he says.

Gidon Bahiri, for foliar nutrient supplier Omex, agrees damaged soils may often be to blame for the poor appearance of many late-sown crops. "If you have compaction you are on a hiding to nothing."

But routine sap tests in the past two weeks over a range of crops show nitrogen concentrations in beet plants have fallen dramatically, says Mr Bahiri. Aprils rain leached much of the N mineralised during Februarys warm spell beyond backward crops reach, he believes.

"We are advocating 6-10kg/ha of N as a foliar spray which will cost roughly £6/ha. It will increase leaf area, and depending on what else is added will help get roots moving to forage for what nutrients are there."

Applying nitrogen this late is always risky, though it may be worth contemplating in a few isolated cases, says Chris Sutton, fertiliser development manager with Crop Care. Assuming there are no other limiting factors growth from here on depends solely on two factors – sunshine and nitrogen, he maintains.

"But applying nitrogen after June 1 can knock sugar contents by 1%. The dilemma for growers with backward crops is that they need more leaf cover now. Day length is shortening and for every day gone by without proper cover they will lose yield.

"Where we applied some extra N as a liquid a few weeks ago we can see some big improvements in root development and leaf cover.

"The decision in mid-July is much more difficult. But as a fire-brigade treatment on a few individual crops an application of 10kg/ha plus manganese may be the way to encourage root development in compacted soils."

Backward beet.

&#8226 Late drilled plants too small.

&#8226 Soil damage main reason.

&#8226 Sap tests show low nitrogen.

&#8226 Late N depresses sugar content

&#8226 Light N/Mn tonic could help.

BACKWARD BEET

&#8226 Late drilled plants too small.

&#8226 Soil damage main reason.

&#8226 Sap tests show low nitrogen.

&#8226 Late N depresses sugar content

&#8226 Light N/Mn tonic could help.

Only a few backward beet crops are likely to justify a nitrogen fillip this late in the season, say specialists.