Good Soil = Good Yield

For Waikato farmer Alan Henderson, maize growing is a key component of his dairy farming operation. Words Heather Chalmers.

Waikato dairy farmer and maize grower Alan Henderson is focusing on soil health and cover crops to improve maize yields.

Taking pride in producing high yielding maize silage and grain crops, Alan Henderson is always experimenting with crop management and inputs with the goal of improving soil health under a continuous maize cropping system.   

Alan runs maize trials for the Foundation for Arable Research and Pioneer each year as well as conducting numerous onfarm trials of his own.
“A paddock which has been in maize for more than 60 years is a consistent play field for me to see what I can do. On the nitrogen front, I am always challenging what type of nitrogen should be applied and which is the most economic.”

Alan and his wife Joy’s Cranleigh farm near Te Awamutu, has grown from the initial 172ha bought by Alan’s parents to 400ha. While the dairy operation is the farm’s key enterprise, there is also a large cropping operation supporting this, with 70ha of maize and 50ha of chicory and turnips for summer grazing.

Of the 70ha grown in maize, 10ha is for grain and 60ha for silage. Maize grain is used for calf meal with the surplus sold for stock feed, while two-thirds of the silage is fed to his dairy herd with the remainder sold. In addition, Cranleigh runs a 600 calf rearing unit, with calves sold at 100kg.

Running close to a DairyNZ System 5 high input dairy operation, supplementary feed is a key requirement to maintain a high stocking rate of 800 Friesian cows on a 215ha milking platform.

The farm feeds 900–950tof maize silage each year as well as 700–800t of imported palm kernel. This equates to 1.2t of maize silage and 800kg of palm kernel per cow. Chicory and turnips are grazed as summer feed. “The purpose of growing these is to supply a protein source to cows in the summer dry which we are getting this year,” Alan says.

When growing crops, dairy effluent is becoming an increasingly important source of nitrogen. “I am spending a lot more on infrastructure, to deliver that nitrogen on to my pasture and cropping areas.”

Improvements have been made to effluent storage, to capture solid effluent, as well as water usage from the rotary dairy. Solid effluent is spread onto the cropping ground while liquid is irrigated onto about 50ha of dairy pasture. “Definitely the effluent solids add, not only a portion of nitrogen, but also to the biological activity of the soil.”

Alan is part of a FAR grower-led group in Waikato trying out alternative sources of nitrogen (N) when growing maize.
A trial in his maize silage crop last year compared areas with chicken manure, dairy effluent, no starter fertiliser and his standard application of granulated nitrogen fertiliser.

Maize silage yields varied from 24 tonnes/drymatter/ha for no nitrogen fertiliser (apart from a base application of 70 units of N), with chicken manure producing the highest yielding crop of 27 tonne/drymatter/ha. “What that indicates to me is that if you have plenty of moisture through the growing season mineralisation provides a lot of the nitrogen required.”

A drier summer was expected to impact on nitrogen mineralisation – soil nitrogen which becomes available during the growing season – and so yields for this year’s harvest. Deep N testing is used to determine soil N levels.

Cover crops improve soil 

Improvement of soil has been Alan’s starting point for growing maize since he began farming about 45 years ago. “You must have good soil to get a good yield.” Initially, the continuously cropped maize paddocks had no worm life and little soil biological activity.

By using a winter cover crop, which is often not grazed or made into silage, but for the sole purpose of adding organic matter, soil health in his cropping paddocks has gradually improved. “It takes time to build structure and a good soil.”

His cover crops have also changed from the more traditional grass to nitrogen-fixing legumes like faba beans which can supply soil nitrogen to the following maize crop. “It is not economic to grow a faba bean green crop compared with applied granulated product for the supply of nitrogen, but what I am looking at is the biological aspect of the cover crop that works into the soil.”

This season another legume, hairy vetch, known as one of the best nitrogen producers and soil conditioners, will also be added.

In long-term maize paddocks Alan has been able to drop applied nitrogen by 2%, from 280 units/ha to 220-230 units/ha.

One paddock has been in continuous maize for grain for 61 years. It hasn’t been grazed for more than 40 years and has solid effluent applied. Other paddocks such as the one used for the alternative-N trial are grazed by dairy cows in winter.

“We should be returning a lot more cover crops back into the soil. People take the cover crop off, or graze it, as it is better financially, but this isn’t beneficial in terms of soil structure, particularly when continuously cropping maize.”

Improvement of soil has been Alan’s starting point for growing maize since he began farming about 45 years ago.

To further improve his soil, Alan has now adopted no till in some paddocks although he has some concerns regarding soil temperatures and planting. “My one ambition was to try and get as high a yield as possible. I am quite disappointed that no grower in New Zealand has yielded 25t/drymatter/ha for maize grain, although some are around 20t DM/ha”

The average maize grain yield is 11t DM/ha Alan’s average maize silage yields are around 23t DM/ha, compared with the Waikato average of about 20t DM/ha.

“Improving the soil is a long journey. Take a small area and do something radical. I’ve always taken the philosophy that you will get a visual soil structure change in three years and a yield change in five years,” Alan says. “I’ve been a person who thinks of something and tries it. Give it a go.”