Increased Effective Rainfall

Soil carbon farming is crucial in enhancing a farm's effective rainfall, particularly in a changing climate. In the Southwest Land Division of Western Australia, average rainfall has significantly declined, posing severe challenges for farmers.

According to the September 2021 Western Australian Climate Projections report by the Western Australian Government (which references projections from CSIRO and the Bureau of Meteorology), the region has experienced a marked drying trend since 1970. This trend is expected to continue, with forecasts indicating further decreases in rainfall and increased drought conditions. Soil carbon farming can mitigate these challenges by improving soil structure and its capacity to retain water.

The Southwest Land Division has experienced a significant decline in rainfall, particularly in autumn and early winter, with a decrease more substantial than anywhere else in Australia. Projections indicate that by 2030, winter rainfall may decrease by up to 15% under low, medium and high emission scenarios. This reduction in total annual rainfall poses a challenge for farmers and intensifies the heavy rainfall events, further complicating their water management.

Effective rainfall, also known as useful rainfall, refers to the portion of total rainfall that is actually available for crop use. Not all rainfall contributes to plant growth; effective rainfall is the amount that infiltrates the soil and is accessible to plants, supporting their growth and development. This concept is crucial in agriculture, as it helps farmers determine water needs for their crops and livestock. 

Enhanced Soil Structure

Soil carbon farming involves supporting soil life, providing fertility to the crop, naturally controlling pests and disease, and maintaining structure to capture rainfall and store soil moisture effectively. With the variety of modern technology available to farmers today, there are many interventions that a farmer can apply to achieve the above outcomes. 

Increased Water Retention

Maintaining a living root in the soil and maximising crop residue retention over summer lowers soil temperatures, mitigates against wind erosion, reduces evaporation and supports soil biological mineral cycling.  Soil porosity, aeration and aggregation is maintained, supporting rainfall infiltration and water retention after a rainfall event. This stored water is then available for plants over extended periods, particularly during dry spells. This increased water retention is critical for sustaining crops and pastures in regions facing reduced rainfall. 

Reduced Erosion and Runoff

Improved soil structure and increased organic matter content reduce soil erosion and surface runoff. When rainwater infiltrates the soil more effectively, less water is lost to runoff, and more is retained within the soil.  

Combating Salinity

Salinity is a significant issue for farmers in the Southwest Land Division. Soil carbon farming can help mitigate salinity by improving soil health and increasing organic matter content. Healthier soils with better structure and water retention capabilities are less prone to salt accumulation. Furthermore, deep-rooted plants and cover crops used in carbon farming can help lower the water table, reducing the rise of saline groundwater. 

Improved Plant Health and Yield

Carbon-rich soils, resulting from soil carbon farming, support healthier plant growth by providing essential nutrients and maintaining optimal moisture levels. This leads to plants with robust, deep root systems that can access water stored deeper in the soil profile, making them more resilient to periods of low rainfall. The result? Even under challenging climatic conditions, better crop yields and more consistent agricultural productivity. Soil carbon farming is a game-changer.