Spring-sown canola delivers fodder and grain
GroundCover™ Supplement Issue: 113 | 03 Nov 2014 | Author: Janet Paterson
Switching from autumn to spring sowing is showing huge promise for fodder and grain, according to recent Grain & Graze research
Spring-sown canola can provide valuable summer and autumn fodder, as well as go on to produce grain with little or no yield penalty relative to autumn-sown crops, according to recent Grain & Graze research in the high-rainfall zone of southern Victoria.
Southern Farming Systems researcher Annieka Paridaen says one of the biggest benefits of spring-sown canola is that the crop can make the most of summer rainfall and establish at a time when there are fewer threats to plant growth.
“In our 2011-12 trial, 80 millimetres of rain in May 2012 and a further 75mm in June left a lot of the site pretty much under water, which made access to sow and manage autumn crops very difficult.”
In contrast, canola plants sown during the previous 2011 spring were, by May 2012, well and truly established, with taproots of 300mm.
“The spring-sown plants were resilient and mature enough to be unaffected by the slugs and redlegged earth mites that posed a real threat to emerging autumn plants and demanded costly treatments,” Ms Paridaen says.
A common concern with spring-sown canola is its ability to recover from grazing during a very dry summer and autumn.
“This occurred in our 2012-13 trial, with the spring-sown canola pretty much deprived of rain until the break occurred in May 2013, apart from 40mm of rainfall two weeks after sowing in November 2012.”
The research team were unsure that the spring-sown plants could bounce back from the three grazing episodes on top of the dry and hot conditions.
“But the crop surprised us and came back with flair,” Ms Paridaen says.
“By the time we were sowing the autumn crop in May 2013, the spring-sown and grazed plants were well on their way to becoming a viable commercial canola crop, without the threats posed by slugs, redlegged earth mites and cold, wet conditions over the winter.”
Grazing commenced at the end of January 2012 when three tonnes per hectare of good quality dry matter was available. The crop was grazed with dry ewes stocked at 26 dry sheep equivalents (DSE)/ha.
Just over 4000 kilograms/ha of dry matter was removed over 55 days of grazing.
The feed quality of the canola was high, with metabolisable energy (ME) averaging 13.5MJ/kg dry matter and protein up around 22 per cent.
Ms Paridaen says nitrate poisoning was not a concern in 2012, with levels well under the toxic threshold of 1000 milligrams/kg for lambs. “But introducing stock to forage brassicas needs to be done gradually and it is important that stock are not put onto canola with an empty stomach,” she explains.
It can take a few days for stock to develop a taste for the canola, Ms Paridaen says, with almost every other plant in the trial area eaten before the sheep started on the canola.
“Monitoring feed levels during grazing is important, as it did not take long for the sheep to completely eat the paddock bare once they became accustomed to the canola.
“In the 2012 trial, the third and final grazing was much heavier than planned due to the sheep eating it down very quickly.”
Grazed canola yielded more than ungrazed canola in the 2011-12 trial, with nearby spring-sown ungrazed plots yielding 1.9t/ha compared to 2.7t/ha for grazed plots. Nearby canola (CB™ Taurus) sown at the conventional time (April) yielded 2.3t/ha.
Grazed plants had more branches and a denser canopy than ungrazed plants.
The number of times the crop was grazed had no significant impact on yield. Grazing twice yielded 0.1t/ha more than a single grazing and 0.2t/ha more than grazing three times (Table 1).
“Although there was a yield penalty by grazing three times compared to two, the third grazing supplied an additional 1t/ha of high quality feed at the beginning of May,” Ms Paridaen says.
Heavy grazing reduced yield compared to light grazing, irrespective of grazing frequency. However, the reduction in yield was small and the heavy grazing produced 4t/ha of feed compared to 1.4t/ha when lightly grazed.
“When deciding on stocking rate and grazing intensity, it will be a trade-off between the value of the feed over summer and autumn and final grain yield,” explains Ms Paridaen.
Canola resilience was well and truly tested in the 2012-13 trial, with three very heavy grazing periods between the end of January and the end of April.
Ms Paridaen says plants were lost and for a while it seemed as if the crop would not recover.
But the thick starchy stem and root system of the established canola enabled the plants to hang on and they started to grow back once the break finally came.
“The recovery of the plants was just astounding,” she says. “By winter 2013 it was impossible to distinguish the grazed and ungrazed plots.”
The 2012-13 trial demonstrated that canola can recover from the stress of complete defoliation and still go on to produce a reasonable grain yield (Table 2).
The 2013 canola generated about one tonne less feed than the 2012 crop, but Ms Paridaen says the value of the green feed during the dry 2013 summer and autumn would most likely have outweighed the extra feed available in the more favourable 2012 season.
“It is difficult to put a price on almost three tonnes of high-quality green feed when there is nothing else around,” Ms Paridaen says.
More information:Annieka Paridaen, Southern Farming Systems,
03 5265 1666,
GRDC Project Code SFS00020
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