Using Variable Rate Technology to address common soil constraints
POD CASE STUDY
In coastal cane-growing locations, paddock yield variability is a common occurrence. The reasons for this variability can range from soil limitations, to location in the landscape, to uneven irrigation application, to inappropriate nutrient and chemical applications. The Point of Difference (POD) Project, funded by the Great Barrier Reef Foundation and Farmacist aims to increase grower understanding of the interaction between these variables that influence crop growth. By utilising precision agriculture technologies and practices, and proven science-based principles, the project is helping growers develop management strategies to increase their productivity while maintaining positive water quality outcomes.
In the Mackay region, sodicity and salinity are two of the most common soil constraints that affect cane yield. Sodicity occurs when the sodium concentration is greater than or equal to 6% of the total concentration of salts present in the soil (measured as an ESP[%] ). The large sodium ions attach themselves to clay particles, negatively impacting soil structure. High levels of sodium cause clay particles to disperse when wet, resulting in sealing and crusting of the soil surface and a dense subsoil which resists root and water penetration. Saline soils are those that have a high concentration of soluble salts in the soil solution (the degree of salinity is measured by Electrical Conductivity [EC]). These salts can be a combination of a number of ions but sodium chloride is the most common. Salinity restricts growth by reducing the amount of water available to the plant. Tony Bugeja and his son Mark farm 330 hectares of cane in the Homebush-Rosella area south of Mackay. While harvesting, they noticed considerable yield variability in a particular paddock (figure 2) and were interested in determining the cause in order to fine-tune subsequent nutrient management practices.
Using drone footage, Farmacist could pinpoint the exact locations of these lower yielding areas in the paddock (see figure 1). These regions were marked with a GPS, so they could be monitored over time. From these identified regions and by utilising soil and EM maps, two sampling locations were determined and soil cores were taken to a depth of 80 cm in the profile. A sample from each 20cm increment was sent away for analysis.
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