Early Post Emergent Deep Ripping: An option for 2024?

By Nathan Craig, WMG Chief Executive Officer

While deep ripping is a common practice across much of the Northern Agricultural region each year, the lack of significant rainfall to date meant that soil may be too hard to rip in 2024. As a consequence, farmers may be considering early post emergent deep ripping in 2024. WMG investigated early post-emergent ripping for grain yield benefit across the Wheatbelt in 2021 and share the key learnings in this article.

Background

Early post-emergent ripping is the practice of deep ripping after the crop has emerged. Typically, this can be completed anytime from immediately following seeding until about 6 weeks following crop emergence. The completion of deep ripping practices after seeding also takes advantage of having plant-based ground cover from the crop to protect the soil from wind events. In contrast, traditional deep ripping practices are completed in the autumn period prior to seeding.

Deep ripping is normally completed in Autumn each year prior to the seeding window in late Autumn. This approach means that often there is a significant yield increase in the crop immediately following the deep ripping, with the benefit decreasing over subsequent years as the soil gradually recompacts.

The process of deep ripping is made easier when there is some soil moisture to allow the ripper to successfully reach the target ripping depth. Nowadays, many farmers are ripping to a depth of 60cm as they are targeting a compaction layer in the 30-40cm soil depth. Stress on machinery and fuel use are very much decreased when there is some soil moisture as it decreases the inherent soil strength, even in sandy soils.

The start to the 2024 season has been exceptionally dry and there has been no significant rainfall to enable deep ripping programs to be completed in full. Farmers are now considering if they should be using early post-emergent ripping as a way of still gaining a benefit in the 2024 season.

Methodology

Four trial sites were located across the Wheatbelt and Northern Agricultural region of Western Australia (WA) in the 2021 season. The sites were established on soil types that tended to be sandy in nature and capable of being ripped to a depth of 60cm and with an identifiable hardpan.

At each site, the ripping treatments were laid out in a demonstration style design with 100m x 12 metre plot width and with two replicates as outlined in Table 1 and treatments applied as specified in Table 2.

The machinery used was provided by the host grower and included the type of deep ripping equipment currently used on farm, including a trailing roller in most cases. Each site was aimed to be ripped to depth of 600-700mm and with a roller of some description to close the soil following ripping. Most ripping equipment was set up for pre-seeding ripping and had more aggressive rollers to reduce clods and level the soil surface.

The site was sown with farmer equipment and all cropping inputs for the season were constant across all treatments, with the agronomy package consistent with farmer practice in the local area. Grain yield was measured by machine harvest with the grower’s harvester using either a weigh bin or harvester yield map.

Results

Grain yield for each site was generally not impacted by the practice of early post emergent deep ripping at each site in this study (Figure 1). The practice of ripping prior to sowing was completed at the Dandaragan and Corrigin sites and this led to an increase in grain yield compared to the control (nil ripping). There was very little difference between grain protein and grain hectolitre weight where these were measured.

The impact of early post emergent ripping at each site had differing effects on crop production (Figure 2). At the Dandaragan site, the aggressiveness of the deep ripper/roller combination had a large and visual impact on plant numbers, and this led to the termination of the site by the farm owner after the 1WAS ripping treatment. Where deep ripping was completed at the Mingenew site at a slight angle (5 degrees) to the direction of sowing, it was evident that annual ryegrass had populated the area where short lengths of crop row (~0.5m) had been pulled out by the ripper as it crossed the seeding row. In comparison there were fewer weeds in the rest of the crop. At the Latham site, plant numbers were low where early post emergent ripping was used, and this was reflected in there being many larger areas (~1m²) where there was no crop growing. Plant establishment was higher at the Corrigin site for the pre-seeding ripping treatment, and this is clear in the early vigour of the treatment compared to the control (Figure 3). The reduction in early plant vigour is evident in the early post-emergent ripping treatment at the Corrigin site.

Discussion

This study has found that the practice of early post emergent deep ripping did not lead to an increase in grain yield in the year of deep ripping that is commonly expected from the practice of deep ripping.

The impact of pre-seeding deep ripping appears to have two benefits in that it tended to increase plant establishment and led to an increase in plant vigour compared to where no ripping had occurred (control treatment). This early vigour likely was a key factor in the higher grain yield for the practice of pre-seeding ripping as even though the soil was loosened with the early post emergent deep ripping, the plant was not able to compensate for the reduction in early plant vigour.

The impact of early post emergent deep ripping was likely exacerbated by the depth of ripping and the aggressiveness of the roller that follows the ripper. Ripping to this depth increases the fracture of the topsoil and tends to achieve a greater level of soil disturbance in general. Where ripping to depth is practiced prior to seeding, a heavy or aggressive roller is needed to break down clods that are raised to the surface during ripping. This aggressive roller was likely causing a significant amount of damage and was often seen flicking up plants and dirt during the ripping process. The limitation to the use of aggressive crumble rollers is that they are often integrated into the structure of the deep ripper and this limits the applicability of most deep rippers on the market. For early post emergent deep ripping to be successful, deep rippers that have low soil disturbance and with a non-aggressive roller may decrease the impact on crop growth. Early post emergent deep ripping may also be aided by greater accuracy in the placement of seeding and deep ripping rows, with wider row spacing likely to lessen the impact of the ripping process, particularly where inter-row ripping is achieved. This is an area for future study if there are growers capable of undertaking this practice.

Significant management issues have tended to arise from the activities of this project. The reduction in plant establishment across all sites from the deep ripping was in part transitory, in that the impact was most visual in the two weeks following deep ripping. In conversing with growers who have previous experience in early post emergent deep ripping, it was suggested to ‘not look at the paddock for a few weeks.’ Overall, plant establishment was lower for pre-seeding ripping compared to early post seeding timings despite each treatment looking visually better after two weeks post ripping. Where the direction of ripping and seeding were parallel, the impact of early post emergent deep ripping was to displace and rearrange the plants in the soil and disturb the rows of crop from seeding. This displacement caused a reduction in growth that has the potential for weeds to establish, compete with crop growth in the year of ripping, and cause issues for the future management of the paddock. Where ripping was conducted at a slight angle to the direction of seeding, this resulted in frequent patches where short sections of crop were removed, leaving a gap in the crop row. This resulted in weeds such as annual ryegrass filling this gap and is likely to cause significant management issues in the future.