Climate modelling suggests warmer average temperatures will make maize silage a more viable option, but the crops will have to be managed differently in the future than in the North Island.
Foundation for Arable Research (FAR) is looking at row spacing and seed number options to raise maize yields.
The thinking is northern row widths of 76 centimetres might not bring out the best for maize productivity or forage quality in the South Island.
On the back of an irrigated trial last year which showed some yield gains from putting a crop in narrow row widths, another small plot trial is continuing at the organisation’s research site at Chertsey in Mid Canterbury.
The books were opened at the site to show growers the maize trial results at FAR’s CROPS 2022 field day.
Researcher Owen Gibson said a 16-row John Deere planter in the small plot had to drill in one direction and then shift across on GPS to return and halve the row spacing for a 76cm and 38cm spacing for the 2021-22 trial.
Between the two row spacings they ran different plant populations of 100,000, 120,000 and 140,000 seeds per hectare.
Some failed seeds did not emerge, and the hoped for significant differences between 38cm rows and 76cm rows did not quite play out.
However, there was still some interesting data to come out of the trial, he said.
"We did produce some really good yields. When we took our hand-cut yield we had 32 tonnes of dry matter in the 38cm rows and 30t/DM in the 76cm rows, so there was a difference, and two tonnes is not a small amount.
"I think if we had more treatments and more points of difference we would have seen a significant difference, so it was interesting to see what we achieved out of it."
About 260kg of nitrogen was applied for the whole plant silage crop yielding 32t/DM. Pioneer hybrid 8666 (CRM 86) was planted on October 28, and harvested on April 8, 162 days after planting.
The spacings were at 30cm, 40cm, 50cm and 70cm rows, with plant populations of 90,000, 110,000 and 130,000 seeds.
"We are trying to follow that whole light interception to see if we are getting the difference between the different treatments.
"As you would expect with narrow rows and more leaves within the rows we had a big difference in the early light interception. But once we were getting up to V5 and V7 [growth stages] we weren’t seeing much difference in intercepted light."
The risk was if this became too high, as crowding stress would cut yields. Hybrids had been used as they could manage stress from over-crowding, but the cut-off plant distance was probably about 13cm, he said.
This year’s trial was planted using a forage brassica planter, because they are widely available in the South Island.
Maize senior researcher David Densley said maize could be planted in the South Island typically once soil temperatures were 10degC and rising.
"Often it’s quite cool in spring time, so osmosis has to hit the ground running and up until V3 all the nutrients for the plant is coming from the seed.
"So right now these plants are pulling the nutrients from them, but that’s about to be exhausted, so very shortly we are relying on the nutrients in the soil to pick up where the seed left off. So starter fertiliser actually becomes really important here."
Starter fertiliser is typically 5cm away from the maize seed and 5cm below it, and research is investigating putting liquid nutrients even closer to the seed.
By flowering, about 65% of the nitrogen had been pulled up by the plant ,with 35% required to be sitting in reserve to get it through the maize silage harvest.
Mr Densley said North Island trials had looked at conventional cultivation, strip till and no-till results, as well as planting in cover crops and nutrient placement, carbon to nitrogen ratios and matching hybrid plants to different soils.
