National Soils Conference 2018: Topsoil Slotting Plates Boost Yields on Sandy Soils
Grain growers with compacted sandy soils could achieve yield improvements of more than 35 per cent by using topsoil slotting plates in association with deeper ripping, according to recent research.
The Department of Primary Industries and Regional Development’s field trials, with co-investment from the Grains Research and Development Corporation, showed topsoil slotting plates provided an additional boost to large yield increases produced by deep ripping.
Topsoil slotting is thought to enhance and prolong the effect of deep ripping, when combined with controlled traffic farming, enabling plant roots to penetrate into the clay.
There has been increasing interest from growers in the use of topsoil slotting plates, however, questions remain regards the benefit relative to the additional cost.
Department research to address these and other questions was profiled at the National Soils Conference 2018 in Canberra this week.
The department’s trials used topsoil slotting plates, 28 centimetres long and 43.5cm deep, bolted behind ripping tines and working 100 millimetres below the soil surface, allowing topsoil to fall down into the ripping slot.
Department research officer Wayne Parker said three years of trials at Moora and Binnu showed a significant yield response in the first two years from deep ripping at 550 millimetres with topsoil slotting plates.
Mr Parker said the results varied depending on crop type and seasonal conditions.
“Topsoil slotting provided a positive response at both sites in 2015, allowing plant roots to access moisture at depth during a hot spring, resulting in an 83 per cent yield increase in canola at Moora and an 18 per cent yield improvement in wheat at Binnu,” he said.
“2016 saw a 33 per cent increase in barley yields at Moora, while at Binnu the increased lupin biomass generated by deep ripping ended up producing excess shade that limited yield improvement to 9 per cent.
“Yields in the northern trial were compromised in 2017 by the late start to the season, low rainfall and hail damage, resulting in a negative response in wheat at Binnu, however, there was a 54 per cent increase in lupins at Moora.
“Topsoil slotting plates appear to have had a positive influence across three years, with the best responses in the first two years after application.”
The department is preparing to harvest the final year of these trials, while complementary trials on different soil types will continue in Ravensthorpe and Salmon Gums.
Mr Parker said while topsoil slotting plates had a role to play when ameliorating soil compaction, their use would have to be considered carefully alongside the cost of the application.
“In addition to the cost of the plates, the extra drag adds 20 per cent to the energy cost of towing the ripper, not to mention the extra wear and tear on machinery,” he said.
“It is also important to note that soil compaction is only one of the soil constraints present in sandy soils. Subsoil acidity and soil water repellence continue to be costly constraints, which are not remedied by deep ripping.
“To get the most from the increased cost of plates, it is better to have the topsoil pH amended prior to slotting to assist subsoil pH amelioration.”