Summer cropping lifts nutrient access
GroundCover™ Issue: 112 | Author: Alistair Lawson
Summer cropping has enabled Tom Dunstan to effectively farm more soil and access nutrients further down the soil profile, as well as grow a more profitable wheat crop.
The Victorian grower farms with his wife Amity and parents, Tom senior and Sue, at Telangatuk East and Lake Karnak in a zero-till, controlled-traffic farming (CTF), continuous cropping program across 2400 hectares. Their winter crops include wheat as the main enterprise, along with barley, faba beans, lupins and vetch. However, Tom says it is their summer cropping program that has delivered significant benefits to the winter program.
Average rainfall of 500 millimetres means that moisture availability is not usually a problem, but rain can sometimes be highly variable. The problem is often too much moisture, leading to waterlogged paddocks or trying to sow in areas that are too wet for a disc seeder.
About 12 years ago, Tom started thinking of ways to make better use of moisture over summer while at the same time expanding his armoury against summer weed control.
“Through a lot of research into soil health, we have found crop diversity through summer cropping is key, and there are other benefits such as managing herbicide resistance,” Tom says.
“The system we have allows for flexibility. We can make money out of residue and moisture over summer, especially in our area where rainfall is reliable. We grow summer crops for a host of reasons, one of which is that maize and sunflowers have deep, aggressive root systems.
“That means we are effectively farming more soil with those crops because of their soil amelioration benefits. Their roots go down as far as 1.4 metres, and the subsequent crops benefit because they get access to nutrients leached from the last 40 years of winter crop farming.
“With more moisture, soil and nutrients, you’re more resilient to risk. We can get more out of our ground.”
Besides maize and sunflowers, Tom's other summer crop options are safflowers and sorghum. In the past, he has also sown a mungbean opportunity crop on the back of good summer rains after winter crop harvest.
While it can vary, up to 15 per cent of the Dunstans’ property is sown to summer crops every year – planted into cereal crop stubble. This is because there is more residue and stored moisture in the soil in cereal crop stubble than in canola or legume stubbles. Tom has not found any disease issues with his summer crops, but like any other crop planted into residue, there can be some establishment pest problems, such as slugs.
Following the winter crop harvest, paddocks earmarked for summer crops are left out of the winter program as a chemical fallow for strategic management of ryegrass. Tom says a prime candidate for a summer crop could be a paddock with a history of winter waterlogging and with a weed population that needs controlling, such as potentially herbicide-resistant ryegrass or wild radish. He can then choose a summer crop to sow in the paddock to suit the seasonal conditions at the time.
At the end of September, fertiliser is banded on the same 762mm row spacings as Tom’s precision planter. It is then left for two weeks until the soil temperature increases before the crop is sown with the precision planter on top of the fertiliser bands, with an autosteer accuracy of two centimetres.
“For example, the soil temperature for corn needs to be 12°C or more,” Tom says.
“Generally, we will plant in the second week of October. For sunflowers, that could be about one month earlier and for sorghum it will be later because the soil temperature has to be warmer. To determine the soil temperature we just use a thermometer and place it at the seed planting depth. We usually do that at 9am for three to four days in a row to see if the soil temperature is rising or falling.”
The average time for harvesting summer crops on the Dunstans’ farm is about mid-April. However, this also depends on the heat over summer and when the crop was planted.
“We try and grow fast-maturing varieties of maize and sunflowers to manage the risk of still harvesting in June,” Tom says. “The maize can be left over winter and harvested in spring because it is resilient to weather damage, but we don’t do that. The trick to a good dryland summer crop is to have an even stand so the whole crop grows and matures at the same time.”
To harvest the crops, Tom uses a conventional draper front with sunflower trays to minimise crop losses. He has been considering investing in a corn front.
“If I did get a corn front I would be able to lower the plant population of maize sown,” he says. “The critical mass required for maize to feed into the draper front is about 30,000 plants/ha, but if I had a corn front I would experiment with 20,000 to 25,000 plants/ha. Down the track I might get one, but it is a considerable investment – anywhere from $50,000 to $80,000.”
Maize needs to be 14 per cent moisture or less to store and is sold as stockfeed. Tom says sunflowers are a lower-risk option, as they can be planted earlier, the seed costs are lower and it is easier to control ryegrass.
“I’d call the sunflowers more a spring crop than a summer crop,” Tom says.
With more than a decade of experience in growing summer crops, Tom and Amity hire out their precision planters to growers all over Victoria who want to grow summer crops. They have two machines, a John Deere Maxemerge Plus and a Case IH Early Riser 1200. Both are 12-row planters on 762mm row spacing.
While Tom sees no-till, variable-rate (VR) fertiliser application and CTF as “the norm” right now, he believes there will be more adoption of zero-till farming in the future.
“We always have to brush up on our efficiency. Fertiliser is expensive – leading to the uptake of VR – and seed is also expensive, particularly with canola leaning towards hybrid seed that is not grower-retained.
“The way I see it, down the track, a portion of our crop will be a no-till, row-crop system so we’re trying to develop an agronomic package to suit that farming system. We are talking about the number of seeds per hectare these days rather than kilograms of seed per hectare. It has been done with maize and sunflowers for years. Growers need a certain amount of plants without overcrowding and the cost of seed helps growers become more efficient and only sow what they need to sow.”
“I believe you don’t need 65 plants per square metre like you’re told; about 20 to 30 plants/m2 will do it. That is what pushed us to precision planters.”
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