Speakers at the recent three-yearly Maize Conference, hosted by the Foundation for Arable Research, made growing maize seem something like an art form these days.

Even the title ‘Beyond our Boundaries' gave a sense of reaching out to further improvements, both in harvest yield and production cost management.

Bob Nielsen, extension maize specialist and Professor of Agronomy at Purdue University, Indiana, provided updates during both indoor and in-field presentations on development in maize growing in the US, since his last visit here.

He produced fascinating details of attempts to increase crop yield since the American Civil War ended in 1865 as the growing of corn became more organised and widespread. In all that time, there have been just two really significant advancements in how it's done.

Better tolerance

In about 1940, when they had got over the Depression and the Dust Bowl years, farmers could finally try out the new genetic technology in the form of double-cross hybrid seed corn, gaining hybrid vigour and better tolerance to stress.
Incremental improvements followed, but the next ‘big thing' happened about 1956, when single-cross hybrids, inorganic nitrogen fertilisers, chemical pesticides and agricultural mechanisation combined to produce a continuing leap in yield from around 3.5 tonnes/ha to the heights achievable on some farms of about 10.7 T/ha.

Silver bullet

Bob warned that no ‘silver bullet' for a further major increase had yet appeared, and the focus had shifted to improvements in drought tolerance, automation, soil mapping, and variable seeding and chemical usage to get the most out of every different area of soil.

While soil tests allow application of variable amounts of phosphorus and potassium fertilisers, plus lime, they have found the situation with nitrogen requirements to be much more complex. The latest views seem to be to put on about half of what might be needed at planting, with further application dependent on a plethora of factors individual to that soil area.

The newest ‘boy's toy' is a ‘Greenseeker' wand, attached to machinery, which measures by red and yellow light, the greenness of leaves against optimums for different hybrids – then producing recommended nitrogen top-up levels.

Spray booms

The problem has been that the most useful time to use this is when the plant is too tall for tractors and ordinary spray equipment to reach, so in some areas they now use spray booms with sensors carried at a height of almost two metres, to apply a top up of nitrogen.

He advised the best way for individual farmers to increase their yields is to work hard and use common sense, including being aware of differences in crop growth and yield across fields throughout the growing season.

Measure plants per hectare, ears per plant, kernels per ear and weight per kernel. Soil drainage and water management can be critical, and tillage methods will differ for different situations.

Most of all, hybrid selection must be studied to get the right ones for the situation, the planting time and the end usage. Nielsen recommends that 'New Zealand maize growers would be well-served by the adoption of a uniform set of hybrid trials wherein variety trials within one or more regions of the country would include a common set of commercially available hybrids”.