Trial 1: Lime comparison trial 
The use of new pH mapping technologies has increased the awareness and identification of soil acidity in many districts. However, there are several aspects of soil acidity management which remain a problem for growers. This trial aimed to investigate a range of lime and acidity management factors outlined in the three key areas below. 

• Lime source 
• Lime rate and particle size 
• Decline of soil pH from sulphur applications 

Trial 2: Comparison of lime incorporation techniques 

Acidic layers of soil are increasingly being identified in the topsoil (0-10 cm) and subsurface soil (10-30 cm) of no-till farming systems. Stratified low pH soil layers need appropriate lime treatment to maintain and prevent the decline of soil pH further. Surface application of lime alone is unlikely to raise the pH in subsurface layers quickly. Recent work has reported lime movement as little as 1 cm – 2.5 cm per year (Fleming et al. 2020, Burns et al 2017). Given the slow movement of lime, incorporation and mixing of surface applied lime to depth is expected to accelerate the movement of lime.

There are a range of machinery options that can provide different levels of lime incorporation and to different depths, such as cultivation, deep ripping with or without inclusion plates, spading and combinations of these. This trial was designed to investigate which of these are most effective on a sandy soil with stratified soil acidity at Bute.

• A lack of grain yield response to lime rates and products trialled at Bute is most likely due to the slightly acidic (pH CaCl₂ 4.8 – 6.1 in the 0-30 cm) nature of the site. However, it is important to monitor soil pH profiles similar to this for pH declines in the future.
• Grain yield response to incorporation method has been variable across the seasons. Lentils showed the greatest benefit in both 2020 and 2023 seasons, while the cereal yields have been unresponsive.
• Treatments which incorporated lime by spading, increased molybdenum tissue concentration (0.35 – 0.37 mg/kg) compared to the no-till control (0.24 mg/kg) in barley in year four.
• Predicta rNod samples taken four years after the trial commenced showed, the application of lime (regardless if surface applied or incorporated) has increased the level of group E/F rhizobia persisting in the soil.
• Both trials contained treatments which have increased soil pH since lime was applied. However, the depth where this pH change has occurred was different in the lime product compared to the lime incorporation trial.