Preliminary results from a GRDC-funded project by Farmlink and CSIRO show that harvesting crops at a high stubble height can increase yield and harvesting speed compared with cutting low and spreading trash.
The trial, in its first of four years, is underway in the medium-rainfall zone on Ben and Lou Beck’s property at Downside, near Wagga Wagga, New South Wales. It uses the Becks’ machinery on a nine-metre controlled-traffic system to apply treatments.
Test strips in a wheat paddock were harvested with a John Deere 9770 STS combine with a 9m front and PowerCast tailboard either as high as possible, where standing stubble was up to 60 centimetres (high), or at about 15cm (low), and straw chopped and spread across the width of the header.
In recent trials in New South Wales, cutting stubble at a high height (60cm) during harvest resulted in increased plant emergence the following year compared to stubble that was cut lower. These photos, taken on 30 May 2014, show the difference in emergence of canola plants sown into tall stubble (above) and short stubble (below).
PHOTOS: Dr James Hunt
Stubble load at harvest was 7.6 tonnes per hectare and strips were replicated and cut at random across the paddock.
High-cut strips were either left tall, cut with a K-Line® Trashcutter following harvest, or burnt in late March. On 19 April, ATR Bonito canola was sown over the trial site using an Excel single disc seeder inter-row sowing on 25cm row spacing.
The main finding from the first year of the trial was that harvesting low reduced yields by 0.14t/ha. More than likely these losses were due to the increased straw bulk. This was despite a much slower harvesting speed when cutting low than high (6.2 kilometres per hour versus 10.6km/h).
CSIRO research team leader Dr James Hunt calculated the cost of harvesting low to be $64/ha compared with harvesting high.
“It’s quite common for growers to manage their stubble at harvest time by cutting it low and spreading the straw. What this experiment has shown is it might be costing more than growers realise,” Dr Hunt says.
In addition, harvest efficiency dropped significantly, from 9.5ha/hour to 5.7ha/hour – a decrease of 41 per cent.
“In south-east NSW, rain during harvest is pretty common so anything that slows down harvest is of real concern. The increased risk of quality losses due to rain is over and above the $64/ha loss from cutting stubble low to the ground,” Dr Hunt says.
After canola was sown into test strips on 19 April 2014, canola plant emergence was measured.
“We found that with a reasonably wet start to the year, emergence was greatly affected by stubble management,” Dr Hunt says.
“The best result was where the stubble had been burnt, which resulted in increased plant emergence of 30 plants per square metre, closely followed by sowing into the tall stubble, where there were 24 plants/m2. By comparison, the low-cut and spread stubble had only 15 plants/m2 and the treatment of cutting tall followed by cutting down the stubble gave a similar result to a low cut at 16 plants/m2.
“In both low-cutting cases, the lower emergence was caused by trash in the inter-row, which interfered with the disc seeder; whereas burning or tall stubble both provided clear ground in the inter-row, reducing hair-pinning, improving soil/seed contact and increasing emergence.”
This difference in emergence results will be assessed after the 2014 crop is harvested.
Dr James Hunt,
02 6246 5066,
End of Ground Cover Issue 112 (Southern Edition)
Read the accompanying Ground Cover Supplement: Ground Cover Supplement Issue 112 - Managed environment facilities
Avoiding stubble trouble
GRDC Project Code