Lentils benefit from stubble support
Lentils are renowned for being difficult to harvest, particularly in dry years when they produce low levels of plant biomass, but the SARDI trials have shown that retained stubble can increase plant height and also act like a trellis holding them up off the ground.
The Grains Research and Development Corporation-funded trials, conducted at Pinery and Mallala in South Australia’s Lower North, compared standing cereal stubble to slashed and removed stubble, which was either raked off or burnt.
The work was conducted by former SARDI research officer Mick Lines and SARDI research scientist Larn McMurray. Besides trying to increase harvestability, they also wanted to find out if providing a trellising structure in stubble would improve yield and potentially reduce disease infection.
Mr McMurray says results were variable across seasons and varieties, but promising.
“Treatments with retained stubble either slashed or standing were higher yielding than removed stubble,” Mr McMurray said. “The standing treatment was generally similar to the slashed stubble. Across three years of trials on alkaline soils ranging in annual rainfall from 302 millimetres to 496mm, a larger yield benefit from the standing stubble was found at the later sowing times. This was most likely due to the moisture conservation benefits from retained stubble treatments being more critical to these later sown treatments.”
Table 1. Grain yield (t/ha) of lentils sown in three stubble management practices across three sowing times at Mallala and Pinery, South Australia from 2010-2012.
|Sowing Time||Stubble treatment|
LSD (0.05) = 0.053, except for same sowing time = 0.045
Mr McMurray says there was also a varietal response among the lentil varieties used in the trial. Yields with PBA Blitz, an early-maturing variety with good lodging resistance and relatively limited lateral plant growth, showed as much as a 30 percent increase in the standing stubble treatments when compared with the removed stubble treatments.
Contrasting this was the variety Boomer which showed a much smaller and variable yield response. Boomer is a vigorous growing green lentil with a significantly lower level of lodging resistance. The erect growth habit of PBA Blitz often fails to cover the inter-row soil space with its canopy as it remains very upright once it has begun to flower unlike other varieties such as Boomer, Nugget or PBA Ace which regularly completely cover the inter-row space.
“With Blitz, you’re often left with some of the inter-row unprotected which may loose soil moisture to a greater extent than other varieties which close the canopy earlier,” Mr McMurray said.
“If you’ve got stubble in the middle of that canopy of Blitz that’s likely to help conserve moisture, that’s one reason why we believe we are getting a greater yield response with Blitz over other varieties.”
In 2013 and 2014 the research changed tact and looked more closely at changes in stubble height rather than comparisons with removed stubble. In these trials no difference in yield occurred between treatments varying in stubble height of 5cm, 10-15cm and 20-30cm.
“At the same time we undertook a number of harvestability measurements and picked up quite significant plant height increases particularly when standing stubble was 30cm or greater,” Mr McMurray said. “Plant height to the bottom pods was also improved and we were getting a biomass increase too. In the standing and slashed treatments we were getting more biomass than the removed treatment. We were also reducing lodging too.”
Mr McMurray says full stubble retained systems can increase insect and pest pressures often resulting in early seedling damage, retarding growth or reducing plant numbers. Vigilant monitoring and prompt appropriate control measures are vital to prevent plant and yield losses in these cases.
Despite the variability, Mr McMurray says, overall, there has never been a negative response from sowing lentils inter-row into standing stubble and it has always improved plant harvestability. Importantly also there was always a yield benefit from some form of retained stubble over treatments where stubble was removed prior to sowing lentils.
“Even if you’re not getting a yield response, if you’re getting a biomass response it’s still worthwhile because by increasing the above-ground biomass you’re improving height to the bottom pods and also setting up for more nitrogen production.”
Larn McMurray, 08 8842 6265, email@example.com
GRDC Project Code DAV00113