Advice on selecting maize varieties to grow under plastic

Richard Camplin, Limagrain's technical trials manager, stresses that whilst it is important to choose a variety that will grow vigorously through plastic cover and produce high yields, it is also just as important that the variety selected will make silage with a good feeding quality.

“The under plastic system has been developed using selected varieties from the Continent that achieve high dry matter yields. Most of these varieties are over 10 years old and have not changed since the system was first introduced.

“However, since then, breeding programmes for maize have become more sophisticated. Now, in addition to bulk, newer varieties can have better nutritional characteristics – in particular starch content and cell wall digestibility. This leads to higher levels of metabolisable energy in the silage, and better animal performance.

“So whilst farmers are always looking for high yielding crops, they can now also maximise the energy yield and density of their maize by sowing modern varieties which have been bred to provide superior feeding quality.”

Maize breeder Limagrain UK is focused on developing LG brand forage maize varieties for the UK market. And for the past three years, the trials programme has also included evaluations of LG varieties sown under plastic. Just as for maize bred for open sowing, the LG breeding programme, selects not just for their DM yield but also their starch potential and digestibility.

Consequently, Mr Camplin says that whenever maize is being sown under plastic it is vital not just to opt automatically for the existing limited range of established ‘plastic' varieties.

“They may look good in the field, but there's more to consider than just bulk. Where varieties with good nutritional characteristics are selected then a higher energy density of silage can be achieved, leading to a bigger boost to animal performance and improving the profitability on livestock units.”

This was demonstrated in a maize under plastic trial carried out last year at a mainstream growing site near Newark in Nottinghamshire. Amongst the varieties sown, were the standard plastic variety Benicia, the improved digestible LG variety Award, and an earlier maturing LG variety Beacon. See table 1.

 Mr Camplin explains: “The highest yielding variety across the whole site was Award, producing nearly a tonne of dry matter more than mainstream ‘plastic' variety Benicia.

“Not only did the more modern genetics in Award deliver a higher yield, but it also showed a higher starch content and better cell wall digestibility than Benicia. So the ME yield per hectare was also greater by 10,572 MJ/ha – that's a difference in milk production potential of nearly 2000 litres of milk from each hectare of crop.”

Table 1: Performance of varieties under plastic in Newark

Mr Camplin adds: “In very marginal conditions, or for later sowing, then Award and Benicia may not be the best choices, because of the shorter growing season available. They would be less likely to reach maturity and their full energy potential, compared to earlier maturing varieties.

“Instead, where conditions are less than favourable, then an early maturing variety like Beacon may be the best option. Indeed, this has been the case in Scotland where Beacon and another early LG variety Hawk, have proven popular and reliable for sowing in plastic systems. This is reflected in Beacon's higher DM and starch content in the Newark trial, whilst delivering the same starch yield as Benicia.

“As maize drilling time approaches, farmers should be considering their variety choice based on how it will fill the clamp and feed out in the ration. Contractors can help ensure their customers maximise the energy content of their clamps by looking beyond dry matter yields, to also take into account the feeding quality and energy potential of a variety.”

February 2012