Maize and its benefits from below

Maize and its benefits from below

30 April 2021

A rhizotron project by Pioneer has uncovered just how long maize roots will grow and how they can benefit your farm’s bottom line and environmental impact.

It’s long been known that maize silage is a proven supplement and ideal partner to New Zealand’s pasture-based dairy farm system, but the science behind it has been scarce.

Not anymore.

For the last couple of years, Pioneer has been on a mission to demonstrate how long maize roots can grow and, in turn, prove the environmental benefits of growing maize.

With the help of a rhizotron – a structure with a transparent panel that allows non-invasive viewing of maize roots – Pioneer sees what happens beneath the soil’s surface and what it’s found are longer roots than anticipated.

“We have always known that maize has a very deep root system but there hasn’t been recent work in New Zealand in which someone has measured the depth of the maize roots,” explains Dr Rowland Tsimba, Pioneer National Research and Agronomy Manager.

“With the rhizotron, we are seeing what happens below the surface and proving how long the roots can grow.”

The project started in spring 2019 with Pioneer wanting to show that maize roots grew longer than 60 centimetres (cm). The maize was planted in black plastic rubbish bags but by Christmas a bag of bundled roots at the base of the bag was the result.

Come the second year, Pioneer built a rhizotron to the depth of 2.5 metres (m) and again, by Christmas, the roots had reached the bottom.

Now in its third year, Pioneer’s built a 3.8m rhizotron, and, not too long after flowering, the roots have reached the bottom.

Seeing just how long the roots grow provides an explanation as to why maize stands to benefit farmers when it comes to their farm system and profit, and impact on the environment.

Not only are the roots taking on water at depth, but also nutrients such as nitrogen that would otherwise end up in waterways.

“Nutrients such as nitrogen are mobile in the soil and move with water in solution,” Rowland explains. “If the nutrients move below the rooting depth, they will potentially be lost, ending up in the waterways.”

“The deeper the rooting system, the greater the chances that nutrients that get washed down the soil profile do not end up in waterways.”

In explaining this, Rowland compares maize’s roots to those of pasture species, which are typically around 60 - 70cm.

“If nutrients dropped below this depth, they will most likely be lost, but with maize, they may not be.”

When nutrients get into waterways, they contaminate the water.

Calling out nitrogen (N) in particular, Rowland explains it promotes the excessive growth of algae which will deprive water of the much-needed oxygen which is required to support the aquatic ecosystem.

On the other hand, the extensive root network of maize increases its water and nutrient extraction zone, resulting in higher maize yields, particularly in situations where both may be limiting.

Maize’s extensive root network allows more dry matter (DM) to grow from every drop of water received.

“Maize has a great summer water use efficiency,” explains Rowland, “almost three times more than grass”.

Important to farm profit is the amount of feed harvested from every hectare (ha), and according to local research, maize silage yields are increasing at a rate of about 200 kg DM per year.

This makes for a cost-effective feed supply to supplement pastures and be stored for months, even years, without loss in feed quality.

By keeping maize silage on hand, it can be called on when needed, such as to stop under- or over-grazing of pasture and allow for pasture recovery.

And even better, most dairy farmers can grow maize with very little, if any additional fertiliser if the paddock is straight out of pasture. It is however recommended that a soil test is conducted to determine the soil nutrient status before making a fertiliser decision.

New Zealand farmers’ ability to produce such great maize yields surprised Rowland when he and his wife put down their roots here 20 years ago.

Originally from Zimbabwe, they were looking to set themselves up for the future and fell in love with New Zealand The move was made even easier with Rowland already working for Pioneer in Zimbabwe.

He grew up on his parent’s crop farm, and though he admits to having no interest in the industry as a child, his profession speaks differently.

Reflecting on the move from Zimbabwe to New Zealand, he says the biggest change he saw on farms was the move from grain-orientated maize farming systems to silage-orientated systems.

He estimates that more than 90 percent of maize in Zimbabwe is grown for human consumption, unlike in New Zealand where the majority is grown for silage.

“We largely grew white maize there – not much of the yellow maize.”

Zimbabwe is also significantly warmer and water and soil fertility are among the key limiting factors for cropping.

When moving to New Zealand, the local Pioneer team embraced Rowland and eased his transition between countries. His love of the team continues today, as does his passion for the farming industry.

He shares in Pioneer’s motivations to support farmers in minimising their impact on the environment, saying while Pioneer is a “seed company” from a research perspective, a huge chunk of our budget is spent on environmental projects.

“For the next few years, you will hear us talk more about that because reducing environmental footprint will help ensure we build a more sustainable industry.

Find out more about maize and the benefits it can offer your by visiting

Article supplied by Pioneer