The Reppel family operate two 100 acre properties east of Mareeba in Queensland’s Atherton Tablelands. One property grows Cavendish bananas, while the other is dedicated to producing the Lady Finger variety. Productivity on the Red Ferrosol soils are favourable for a variety of horticulture in this region with high plant available water capacity, high permeability and sufficient drainage. Surface soils are slightly acidic (pH 5.8 – 6.5) red-to-brown clay/loams with moderate structure, while the neutral (pH 6.8 – 7.5) subsoil consists of light clay with gravels and cobbled derived from basalt rock. Variation in altitude and proximity to the Great Dividing Range produces a diverse micro-climate across the Tablelands. Average summer rainfall over the Tablelands is significantly lower than the neighbouring coastal region, thus the water requirements for banana production depend primarily on irrigation. Like many growers in the region, the Reppel family are connected to the Mareeba-Dimbulah Water Supply Scheme, drawing water form the Tinaroo Dam and other watercourses. Production across the Tablelands and other coastal regions of North Queensland account for 94% of all bananas supplied to Australia, and they are the highest selling supermarket product by volume. They industry is a major economic driver and employer of these regions, employing over 9,600 people across 250 business entities growing on a total of 11,000 hectares.
The banana industry in the Tablelands has the highest Gross Value of Production (GVP) of all tree crops, including mango and avocado. Anticipation among the industry to increase production reflects strong consumer demand in Australia, particularly as the price per carton are forecast to remain at the current index. For banana growers like Mark Reppel and his family, this requires achieving the highest fruit quality standards, minimising plantation damage and practicing sustainable land management to meet new yield targets. Experience in tropical irrigated horticulture has awarded the Reppel family a thorough understanding of the water and nutrient requirements for growing bananas, but maintaining consistent fruit size in higher yields was a challenge. The drip irrigation scheduling needed to be precise in matching the water needs of the crop, while minimising surface runoff and deep drainage below the rootzone. Determining plant available water holding capacity (PAWC) through root activity, the infiltration rate and subsequent permeability down the soil profile would be the key factors to re-scheduling the irrigation management.
Soil moisture monitoring equipment from Sentek Technologies was chosen by the Reppel family to gain a full representation of the banana plantation’s water use. The EnviroSCAN® probe provided precision monitoring of soil moisture at multiple depths in the profile, continuously logging field data to Sentek’s IrriMAX® irrigation scheduling software via a data transmission unit. The EnviroSCAN® probe was installed to measure soil moisture levels at 10cm, 30cm and 50cm intervals, where most of the active adventitious roots lie beyond the underground stem. Observing changes in the soil water dynamic was the fundamental basis for making informed management decisions, and the Reppels, along with trusted irrigation consultants, used Sentek’s highly rated IrriMAX® software to achieve this. This intuitive graphical interface provided the functional workspace to define critical banana growth stages, based on root development, optimise the lateral spread of water through pulse irrigation, and contain fertiliser to the top 50cm of the soil.
With the help of experienced commercial irrigation consultants, Mark Reppel was able to employ the Sentek EnviroSCAN® to improve irrigation management with impressive results. Sensors measuring soil moisture on the probe at the three intervals ensured appropriate water content in the top 50cm was maintained throughout periods of pulse drip irrigation, resulting in an overall 50% increase in yield. The extent to which roots extract water at different depths was fully realised with Sentek’s soil moisture monitoring solutions, meaning a wetting pattern for the soil type was properly defined between rows of the plantation, and surface infiltration rates. Interpreting soil moisture data from the EnviroSCAN® probe was the basis for implementing new drip emitter spacings and different irrigation flow rates to match the infiltration rate and the permeability down the soil profile. As a result, optimal crop water use and improved fertigation efficiency minimised solute lost through subsoil drainage and leaching. Nutrient fertilisers that were now maximised by the plantation meant that in addition to a significant yield increase, overall fruit quality was achieved without the cost of increasing inputs. The plantation was consistently irrigated with 4.0 ML per hectare in the past, and the Reppel family have managed to make gains in productivity using marginally less water – 3.5 to 4.0 ML per hectare using the newly introduced irrigation schedule.
Mark’s experience over the past 2 years, along with the assistance of specialized irrigation and nutrition management, has allowed him to maintain fruit quality and quantity. Having acquired knowledge of the importance of irrigation management has also prompted Mark to seek advice from Fabian Gallo of HydroTech Monitoring, to schedule irrigation in his macadamia nut plantation later this year.
Sentek would like to thank Mark Reppel for taking the time to inform us of the success he has had using the EnviroSCAN® and the IrriMAX® software solution as well as local Sentek distributor, HydroTech Monitoring and Fabian Gallo, who was the Irrigation advisor on the property.