TREATED BEET THROWS LIGHT ON FERTILISER
ACCESS to Advantage-treated sugar beet seed could turn previous thinking about the value of starter fertilisers on its head.
"Until recently most experiments with starter nutrients band-placed for the crop at sowing have failed to mirror the benefits seen in vegetable crops," says Peter Saunders of NIAB, formerly with ADAS.
But trials on fen soil at ADAS Arthur Rickwood in 1997 and last year suggest those findings may have been because drilling dates were not early enough to make the most of the fertiliser.
Alternatively the emerging seedling roots did not grow fast enough to reach the fertiliser before it became too diluted or leached.
The arrival of a seed treatment which gets seedlings away sooner could change all that, especially with early drilling in cold soils.
"Given the right combination of seed type, drilling date, soil condition and fertiliser placement there does seem to be some value in starter fertiliser for sugar beet," says Mr Saunders.
The full-scale field trials on fertile peat soil, sown early at high plant populations, follow two years of pilot studies. Liquid diammonium phosphate (DAP) was compared with an experimental fertiliser made from commercial powders used in hydroponic systems.
Each was applied through a tine working just ahead of the drill row 4cm (1.6in) below seed depth. Both fertilisers boosted root yields. "And there were no deleterious effects on emergence as seen in some earlier work," says Mr Saunders.
Output using standard seed and the experimental fertiliser was lifted by 2.3t/ha (0.9t/acre). But with Advantage seed the same placed nutrients gave an extra 7.3t/ha (2.9t/acre). Results from diammonium phosphate were similar, albeit slightly less marked.
Compared with using standard seed alone, the combination of starter fertiliser and advanced seed increased ground cover by 15% by the end of May. "That could help with weed control, especially on peats where robust programmes often need to be applied to tender crops," he says.
"The results show that starter fertiliser is more beneficial when using Advantage seed."
The sole downside, apart from the £2500-3000 cost of equipment that might be needed for an eight-row drill, is that amino-N levels in the crop rose in all cases where an injection tine was used – even when no starter fertiliser was applied. That would reduce the efficiency of sugar extraction, he notes.
He suspects tine movement through the soil, which increased nitrogen mineralisation, or slightly increased seed depth could be to blame for the higher impurities. But until the precise reason is discovered and more work is undertaken on different soil types, he is reluctant to advocate widespread use of the technique on soils other than peat.
One eventual outcome might be that growers could trim overall seed-bed fertiliser dressings. In the trials all the starter fertiliser represented an addition to standard dressings, he notes.
• New trials, fresh thinking.
• Big benefit on advanced seed.
• Better early season ground cover.
• Possible weed control spin-off.
• Impurities increased.