Ovine Observer

Transformation of saltland areas at Katanning Research Station

Introduction

Setting a target for Katanning Research Station (KRS) to become carbon neutral by 2030 created an opportunity to revegetate the salt-affected areas at KRS. This came at a time when station management were planning solutions to address the expansion of salinity. This also created an opportunity to demonstrate a range of techniques for rehabilitation of the salt affected land at KRS including the establishment of salt-tolerant pastures for providing out of season feed to reduce the amount of supplementary feed required during autumn and to defer graze annual pastures.

Key findings

• This was land of low opportunity cost – unable to be economically cropped, growing unproductive barley grass, samphire and bare scald. There is a shallow, saline watertable, and the paddock was often waterlogged in winter/spring.
• There was no rain between when the Anameka® old-man saltbush was planted in September 2023 until the first grazing on 17 April (6 months), yet the Anameka® tapped into the water table and was able to be grazed.
• Supplementary feeding has been reduced by 30% and other annual pastures paddocks are protected from over-grazing. There is also the added benefit of the Anameka® providing vitamin E and protein to weaners.
• The implementation has been costly but has improved the current value of land and is an investment in the future – these paddocks will be grazed in the Autumn for the next 20 years.

Site preparation

30 ha at the north-east corner of KRS had previously been used as a saltbush trial in the early 1990s. These were old selections of saltbush species, some no longer grazed and as such had become woody and unpalatable.

We commenced in March 2022 by slashing the saltbush areas with a heavy-duty slasher to break up and mulch the woody material.

In April 2022 we employed a contractor with a heavy-duty disc plough to plough the entire 80 ha to further break-up and incorporate the woody material as well as help aerate the soil profile.

As soil dispersion tests indicated that the site was sodic, in May 2022 we employed a contractor to apply 1.3 t/ha of gypsum and further cultivate the soil several times with prickle harrows to break-up the clumps of clay and incorporate the gypsum.

Due to a high level of Guildford bulb which needed to be controlled, the whole area was seeded to oats in June – July 2022 to be used as standing fodder.

Conditions at seeding during June – July were wet and completing seeding in a timely manner was a challenge.

In September 2022 we employed a contractor to spray the site with 20 g/ha of Chlorsulfuron to control the Guildford bulb and then in October 2022 we sprayed the site with Glyphosate to provide a hay freeze effect and prevent seed shedding and future volunteer oats emerging. Weaners grazed the site between November 2022 – January 2023.

Site characteristics

A whole of farm  EM38 survey was conducted in February 2021 and May 2022, producing a colour thematic map showing the salinity classes (Figure 1).

The paddocks outlined in black show those that have been planted to saltland pastures.

Salinity in the surface soil horizon (0 – 50 cm) is mostly in the moderately saline range of 100 – 200 mS/m (green areas on map) with some highly saline areas shown as yellow, these are in the 200 – 250 mS/m range. These areas are bare or growing a sparse cover of samphire and barley grass.

There are some mildly saline areas (50 - 100 mS/m range) which are generally associated with slightly elevated sandy rises (shown as light blue in Figure 1).

Given the high soil salinity it was decided an alley system of deep-rooted saltbush was required with salt tolerant species in the interrow.

Figure 1: EM38 survey of the eastern end of Katanning Research Station in the 0 – 50cm depth range. 16b (3ha), 16a (5ha), 17b (14ha) A1 (21ha), A2 (17ha), A3 (17ha) paddocks were all sown to Anameka saltbush, 17a (14ha) was direct seeded.

There are 3 piezometers in paddock 17 (north-eastern paddock in Figure 1 outlined in black) ranging from west (P17W) to east (P17E).

Water levels are measured quarterly in these piezometers.

The water level ranged from between -0.15 to -0.3m below the ground surface in September 2023 to between -0.7m and -1.5m in March 2024 (Table 1).

The presence of this shallow watertable in winter – spring suggested belts of deep-rooted saltbush were required to reduce and maintain the watertable at a lower depth.

The salinity of the water ranged from 1500 mS/m (approximately 30% sea-water) to 5500 mS/m (sea-water).

Table 1: Water level and salinity data collected from 3 piezometers in paddock 17 at Katanning Research Station

Soil testing

A soil profile description was conducted as part of the baseline soil assessment  to measure changes in organic carbon due to revegetation. The soil description at the eastern end of Paddock 17 showed the soil consisted of a gritty coarse sand in the topsoil over a sodic clay starting at 40 cm (Figure 2).

Figure 2: Soil profile description in paddock 17b at Katanning Research Station

A soil analysis was done on each profile layer and organic carbon ranged from 1.11% in the 0-10cm layer down to <0.1% in deeper layers (Table 2).

Soil pH was 5.4 in CaCl2 at the surface and was 4.4 (acidic) in the 80-120cm layer.

We used Saltland Genie tool to convert the Electrical Conductivity (EC) reading from a 1:5 unit to an extract (ECe). This converted the 204 mS/m EC1:5 to 1600-3200 mS/m ECe (severely saline).

The exchangeable sodium percentage (ESP) ranged from 5 at the surface to 28 at depth. Soils are considered sodic when the ESP is >6 and highly sodic when the ESP is >15.

Species selection and layout design

Due to the variable soil salinity conditions across the site (Figure 1) a mix of Tall Wheat Grass (10 kg/ha), Puccinellia (1 kg/ha) and Kikuyu (1 kg/ha) was drilled in early September 2023 using a Bourgault airseeder. The seed was blended with 50 kg/ha of a mix of 70% Mono-ammonium Phosphate (MAP) and 30% Muriate of Potash (MOP) to enable the required seeding rate.

Following the seeding, a contractor was employed to plant twin rows (2.5 m apart) of Anameka® old-man saltbush with 2.5 m between shrubs within the row and a 10 m interrow between the twin rows.

The site was ripped to a depth of 30 cm and the nursery seedlings were planted as deep as possible with a shallow mound created to harvest water.

A smaller paddock (13 ha) was also established using the direct-seeding method as a comparison.

An experienced contractor was employed to direct-seed a mix of old-man and river saltbush using a Kimseed saltland seeder, with a seed/vermiculite mix placed 2 m apart directly on a shallow mound followed by a press-wheel.

Due to the dry spring of 2023, the interrows across the whole site were re-seeded with a mix of 10 kg/ha Tall Wheat Grass and 5 kg/ha of Neptune Messina from 22 – 29 May 2024.

As a comparison, some of the moderately saline interrows in one paddock have been sown with Kraken barley to be used as a standing fodder and to enable further grazing in spring 2024.

Establishment

There was a 19 mm rainfall event during planting on the 14 September 2023 and then a smaller 5 mm rainfall event on 18 January 2024. The next substantial rain event was 14 mm on  2 and 3 May 2024.

Due to the dry spring of 2023 and limited summer rainfall the majority of the Tall Wheat Grass, Puccinellia and Kikuyu had died or failed to germinate because of the dry conditions.  Despite this, the survival of the Anameka®  forage shrubs has been excellent with 80 – 90% survival. However, the direct-seeded saltbush has been patchy where germination was poor and these will be in-filled with nursery seedlings in August 2024.

Grazing management

The site has been fenced into 5 separate paddocks ranging from 13 ha to 20 ha each with laneway access and separate troughs. A mob of approximately 600 weaners has been grazed in each paddock for about a week before being moved onto the next paddock when there was 10-20% leaf material remaining on the shrubs (Figure 3). Grazing occurred from mid-April till the end of May 2024 (6 weeks).

Hay was provided at the opposite end to the paddock to the water trough, as was the supplementary trail feed, to encourage the weaners to move away from the trough and graze the saltbush in a uniform manner.

During grazing, the normal grain supplement was able to be reduced by 30% compared to what they would have normally been fed on a dry, annual pasture.

Further refinements to the trough location and trough capacity will be made to improve the uniformity of the grazing.

Other benefits provided by the saltland pasture include the protein and Vitamin E provided by saltbush, and the ability to defer other pasture paddocks and preserve ground cover.

In summary, our plan has been to transform this area at the eastern end of KRS into a saltland pasture grazing system that can support sheep through the autumn feed gap.

We have selected land of low opportunity cost that was unable to be economically cropped and was previously bare scald and unproductive barley grass, samphire and woody/rank saltbush.

Provided the grazing management practices are followed, then the station management can expect to get 10 – 20 years of out of season autumn sheep feed from this investment in the saltland pastures on previously unproductive land.

Figure 3: Anameka saltbush at Katanning Research Station which had just been grazed. Sheep were moved from the paddock when there was 10 – 20% of leaf remaining.