Researchers at Van’s Lab have created a comprehensive scorecard to evaluate and improve soil health. This decision-support tool identifies and prioritizes short-, medium-, and long-term strategies for soil restoration and maintenance, ultimately optimising crop productivity.
Soil sampling: To initiate soil analysis, collect both disturbed and undisturbed (core) soil samples from three distinct depth intervals: topsoil (0-300 mm), subsoil (300-750 mm), and deep subsoil (750-1500 mm). You can choose to collect samples yourself with the guidance of Van’s Lab’s DIY video tutorial or request assistance from their experienced technicians. Accurate sampling, packaging and transport are crucial for reliable analysis (Figure 1), and following these guidelines ensures representative samples for further evaluation.
Illustration of core sampling and packaging of a soil sample, ready to be courier to Van’s Lab for analysis. Once training been completed sampling can be done by yourself, or request assistance from our technicians.
Soil analysis: Our soil analysis aims to assess the physical condition of the profile through specific indicators, each scored relative to its optimal target within a soil texture class. These indicators encompass the three states of matter: solid, air, and water. In the solid state, key properties include sand, silt, clay, stone, and organic matter content, which occupy space and determine total solid volume or its inverse, total porosity. For the air state, two parameters are crucial: Field Aeration Capacity (FAC) and Saturated Hydraulic Conductivity (Ksat). Lastly, water state is represented by water storage, expressed as percentage and volume (mm per soil depth interval).
Rationale of the Soil-Physical Scorecard: The soil-physical scorecard simplifies the complex relationship between soils and crop performance, focusing on the critical rooting system. A healthy rooting system relies on optimal soil pore quality, or “soil infrastructure,” comprising three key components: Firstly, the Transmission Pores (Road Network). These large pores facilitating water, nutrient, salt and air transport in the soil. Size (capacity) and quality (pore connectivity) are crucial, measured through Field Aeration Capacity and Saturated Hydraulic Conductivity, respectively. Secondly, water storage pores (Dam Capacity): These medium-sized pores holding water for plants to extract, similar to farm dams. Both size (percentage/volume) and quality (assessed in Chemical Scorecard) are vital for proactive water management and mitigating water-stress risks. Lastly, Hydroscopic Water Capacity (Micro Pores). These tiny pores retaining tightly bound water, unavailable to roots, where nutrient exchange occurs between water and solids. The role of these pores relates more to the fertility component of the soil and the impact thereof is captured in the Soil Fertility Health Scorecard, not discussed in this article. However, soil particles tend to cling together, resisting root growth. Roots must exert force to push aside these particles as they explore the soil profile, and this resistance is measured as soil strength in the scorecard.
By pinpointing soil infrastructure weaknesses, the scorecard enables farmers to make informed, targeted improvements for optimal crop growth. A real-world example is included to illustrate the Soil Physical Health Scorecard’s practical application.
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Figure 2: Peacan orchard in the central parts of South Africa planted in a Molopo soil form
Case Study: Pecan Farm in Semi-Arid South Africa
Location: Semi-arid climate zone, central South Africa
Soil classification: Molopo soil Form; orthic A, yellow apedal B overlaying soft carbonate; Soil Depth: 1.2 m, Loamy Sand texture class
Volume representation of the soil’s infrastructure for the top-, sub- and deep subsoil; FAC = Field Aeration Capacity, WSC= Water Storge Capacity, HWC=Hygroscopic Water Capacity
Soil physical health scorecard results
To interpret the scorecard:
- Aim for an > 80% total score in top-, sub-, and deep soil.
- Identify indicators scoring below 8 points.
- Consult Van’s Lab’s for targeted strategies to address shortcomings.
Soil physical health scorecard of the individual properties in the top-, sub- and deep subsoil (Scores out of 10, Total =%)
Tabel 1: Soil physical health scorecard of the individual properties in detail
For more information you can visit the Van’s Lab webiste or get in contact with Lindi (+27)76 89 71512, Lindi@vanslab.co.za or Roelof (+27)827 67 2922, Roelof@vanslab.co.za. They are situated at 2 Populier Avenue, Bainsvlei, Bloemfontein, 9338.
