Thursday, 02 September 2021 07:55

Sustainability of maize silage

Written by  Ian Williams

New Zealand research and farmer practice shows that pasture-based dairy systems supported by maize silage can be highly profitable. I have written about this topic extensively in the past.

There is an increasing amount of data that shows maize silage systems are not only good for profit but that they are also good for the environment.

I have previously written about the fact that maize is a deep rooting plant capable of drawing nutrients from depth and that because it produces high dry matter yields, it has a relatively high demand for nitrogen (N). In fact, every tonne of maize silage drymatter harvested removes 12-13kg of N from the soil.

Until recently, we were lacking robust New Zealand data on N-loss under a maize silage, catch crop system. Because there is increasing regulatory pressure on farmers to reduce nitrogen losses to water, we felt that it was important to address this.

My colleague Dr Rowland Tsimba and the rest of the Pioneer research team set up a trial specifically designed to measure N loss from a maize silage/winter catch crop system.

The trial began in the spring 2018 and was designed as a randomised complete block design. The plots had maize growing in them over summer, followed by four winter catch crop treatments (fallow, oats, oats + annual ryegrass, annual ryegrass). Nitrogen loss from these plots was measured using an elaborate (and expensive) ceramic sampling cup system and lysimeters placed below the plot at 70cm and 120cm depth.

The results of this trial are shown in the graph below.

Ian Williams Nitrate Graph FBTW

 

What have we learnt from the trial?

Catch crops work.

The ryegrass and oats catch crop treatments showed a 90% reduction in N loss when compared to the fallow treatment.

Catch crops reduce N-leaching.

Catch crops need water and nitrogen to grow. They help reduce N-leaching by using soil nitrogen and water. The water is used for transpiration and this reduces drainage.

The depth at which you measure N-loss under maize is important.

Because maize is a deep-rooted plant, 70cm (the standard measurement depth for pasture plants) is too shallow to measure N loss from maize silage catch crop systems. In the Pioneer trials the N loss at 70cm was 3.5 times greater than that measured at 120cm.

How deep can maize roots go?

For most of my career, I have parroted what I was told when I first started working with maize, namely that maize roots grow to two thirds the height of the plant. Pioneer's research team wanted to see whether this "fact" was accurate, and they so build a rhizotron is a tall box of soil which has a perspex front closed off by doors to exclude light.

The researchers planted maize at the top of the box and root depth was measured weekly. A week after tasselling, the maize roots had reached the bottom of the box... 3.8 metres deep!

Those who read my column regularly know how important good science is to me. This is great science which will be peer reviewed and published. We plan to use it to help drive the development of sustainable farming systems. There is more to come, so watch this space.

Ian Williams is a Pioneer forage specialist. Contact him at This email address is being protected from spambots. You need JavaScript enabled to view it..

More like this

The potential of under-sowing forage maize

Given that New Zealand farmers are being expected to improve their environmental footprint, some trials in the UK around under-sowing in growing forage maize crops may have some benefits here too, particularly in the south.

Rain rejuvenated maize crop!

OPINION: I am a maize tragic. While that may come as a surprise to some, those who have read this column over the last few years will know exactly where I am coming from.

Why it's never too late to plant

Reports are coming in from across the country indicating the cold and wet spring has meant many farmers and contractors planting crops are behind with their planting schedule.

National

Feds stalwart to step down

Outspoken Federated Farmers leader Chris Lewis is stepping down from the farmer lobby after 17 years of service.

Machinery & Products

India boosts fert subsidy

India plans to double its budgeted 2021-22 fertiliser subsidies to a record of more than 1.55 trillion rupees (US$20.64 billion)…

Kicking lameness into touch

Lameness in dairy cows can have a significant effect on a businesses' bottom line, with vets suggesting that each case…

Single row concept delivers results

While Controlled Traffic Farming (CTF) has become increasingly popular over the last decade, German company Amazone is looking to take…

» The RNG Weather Report

» Latest Print Issues Online

Milking It

Fake and cheap

OPINION: First they demanded plant-based 'milk', now they want it priced cheaper than real milk.

Cannon fodder?

OPINION: The recent high-profile Mycoplasma bovis announcement from the Government in Hamilton featured Prime Minister Jacinda Ardern and Agriculture Minister…

» Connect with Dairy News

» eNewsletter

Subscribe to our weekly newsletter