Trials reveal starter fertiliser benefits for maize under film – Farmers Guide – Jim Clark, Tim Kerr

Maize growers could see a worthwhile benefit from applying a starter fertiliser to crops grown under film, according to results from Hutchinsons trials last season ...

Diammonium phosphate (DAP) starter fertiliser is fairly common practice in open-ground maize, but has not traditionally been thought necessary in protected crops, where the warmer soil increases availability of nutrients such as phosphate. Other financial and technical limitations may also have prevented it from becoming common practice.

However, the large plot trials at the Carlisle Regional Technology Centre found tangible benefits to establishment, root development and biomass growth, that translated into higher dry matter yields last autumn.

Vigorous establishment

Plots of P7034 maize were sown on 18th April 2020 under Samco green film using a specially modified drill fitted with a micro granule applicator. This applied different starter fertilisers with seed, including the ammonium phosphate-based Primary-P, Crystal Green and a new development product called Biolite.

Hutchinsons agronomist Jim Clark says all plots that received starter fertiliser established quickly and looked physically bigger than the untreated maize, with test digs revealing noticeable benefits to early root development. Crystal Green looked particularly impressive early on, but it was Biolite and Primary-P that topped the results after harvest, increasing dry matter yield by 3.2 per cent and 3.1 per cent respectively.

While it is important not to read too much into one year’s results, the findings do indicate that it may be worth reconsidering the benefits of starter fertilisers in maize under film. This is especially true in more marginal maize-growing areas like the northwest, or where crops are sown late and need to catch-up, as research indicates maturity can be pulled forward by about a week where starter fertilisers are used, Mr Clark says.

“We’ve seen starter fertilisers can deliver a benefit on paper, and they are a useful management tool, even under film.”

Jim Clark, agronomist

Changing nutrition strategy

Phosphate is the most important nutrient for root development and maize establishment, especially in the first 30 days after drilling, Hutchinsons crop nutrition manager Tim Kerr adds.

Tim Kerr, crop nutrition manager

There is only a finite amount of phosphate in the immediate root zone, which is likely to run out before maize can establish properly, so starter fertilisers ensure phosphate and other key nutrients are immediately available to the developing seed during this crucial period. This allows the crop to quickly develop a more extensive root system capable of efficiently “mining” soil nutrients and water through the season, he says.

Targeting nutrition more precisely with starter fertilisers could reduce the need for applying granular nitrogen or urea to the seedbed, Mr Clark continues. Growers can save this nitrogen for a foliar application as late as possible in the season when it is in greater demand by the crop.

This should improve nitrogen uptake efficiency and keep crops nourished further into the growing season, he says. It could also benefit early weed control as applying bagged nitrogen to the seedbed often feeds weeds as well as the crop.

Scaling-up trials for 2021

Mr Clark plans to repeat the starter fertiliser trial this year, potentially on a larger half-field scale given the encouraging results in 2020.

This will run alongside other trials – one of which will examine how starter fertilisers can be used in combination with an early maturing variety to successfully grow maize in open ground.

Another trial will investigate whether the establishment boost from starter fertiliser can offset some of the heat lost when using narrower films covering 50 per cent of the field rather than 67 per cent.

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