Date
2022/03/10
Duration
5 min read
ebook
Soil Quality: 7 Soil Water Repellence
Organisations
SoilsWest
Department of Primary Industries and Regional Development
Murdoch University
Grains Research and Development Corporation
Aim: To compare a range of strategic deep tillage treatments for managing multiple constraints; soil water repellence, soil compaction and subsoil acidity

Comparing soil strategic deep tillage implements
Addressing the range of soil constraints present maximises productivity and profitability in the long-term. From Soil Quality: 7 Soil Water Repellence (Davies et al. 2021).
Key messages
In the first season, deep soil loosening was critical for improving yields, however, inclusion of deep mixing or soil inversion to remove soil water repellence while also loosening the soil resulted in larger long-term benefits. Higher yields and shoot potassium concentration are indicative of improved access to water and the soil potassium supply. It is important to address the range of soil constraints present in order to maximise productivity and profitability in the long-term. When undertaking on farm testing of various amelioration methods it is important to monitor the outcomes for several seasons.
- Soil type: Water repellent sand grading to clayey sand over gravel
- Growing season rainfall: 323mm
Experimental treatments
Location: Meenar
The replicated plot experiment, which began in 2016, tested thirteen treatments compared with an untreated control:
- four deep ripping treatments, to 400 or 700 millimetres, without or with inclusion plates to achieve topsoil slotting
- two treatments of spading after deep ripping to 400 or 700 millimetres
- a maximum mixing treatment with spading after deep ripping to 700 millimetres with topsoil inclusion
- four treatments of soil inversion using either a one-way plough alone or after deep ripping to 700 millimetres or mouldboard plough either alone or (in 2017) followed by deep ripping to 700 millimetres
- two treatments which consist of delving followed by spading, either at normal speed or a slower speed were added in 2017.
The treatment plots were located in the wings of the seeder in a controlled traffic system and was sown and managed with the rest of the paddock using farm machinery.
The site was assessed for soil water repellence, soil pH, nutrients and soil strength. Nutrient concentrations in whole shoots, biomass and head number were assessed each season. Grain yields were determined using a small plot harvester and grain samples were collected from each plot for grain quality assessment
The treatments were applied once only and residual benefits have been monitored for 6 years.
Results
The results presented here are for the treatments applied in 2016.
First season after treatment
Soil water repellence was completely overcome by treatments that included ploughing or spading but ripping alone or with inclusion plates had little effect.
In addition to reducing the soil water repellence, each strategic deep tillage loosened the soil profile to its working depth. Soil strength in the control was high – greater than 2.5 megapascals from 220 to 420 millimetres soil depth. All of the implements reduced this strength to below 2.5 megapascals, but for those treatments which included the deeper ripping to 700 millimetres, soil strength was reduced to less than 2 megapascals to a depth of 580 millimetres.
In the first season, all of the treatments yielded more than the control. The largest responses in yield were for deeper ripping (700 mm) which yielded 0.8–1 tonnes per hectare above the control. The mouldboard, one-way and deep ripping to 400 millimetres increased yield by 0.2–0.3 tonnes per hectare. Ripping to 400 millimetres with inclusion increased yield by 0.6 tonnes per hectare, while ripping to 400 millimetres plus spading and one-way ploughing increased yield increase by 0.8 tonnes per hectare. Seeding problems and loose soil meant poorer establishment was achieved in the mouldboard and one-way plough treatments, which did affect yield.
Longer term treatment impacts
Cereal crops were sown for three years following treatment implantation in 2016 with wheat grown in 2017 followed by barley in 2018 and 2019. For these crops those treatments which included spading (deep mixing) or soil inversion ploughing tended to yield more than the deep ripping treatments for the season that cereals were grown.
Those treatments which included spading increased wheat yield by 24–33%
After the first season, increased yields were associated with treatments which reduced soil water repellence as well as loosened the soil. Whole shoot issue testing also revealed that most of the treatments, increased the shoot potassium concentration, some significantly so, which, together with higher yield, imply improved access to the soil potassium supply.

Reference
ebook Soil Quality: 7 Soil Water Repellence
Davies S, Fisher J, Roper M and Murphy D (2021).