Arriga Plains Water and Soil Quality program gets underway

Mitchell River has received a community grant from Northern Gulf to undertake a collection of water and soil quality in the Arriga Plains.

A greater part of the Mareeba-Dimbulah Irrigation Area (MDIA) is located in the Mitchell River Catchment, via the Mitchell River and Walsh River.  The Cattle Creek sub catchment forms part of the Walsh River catchment and is located approximately 16km west of Mareeba, with the creek running 22.5km north-south.  Most of the agriculture in the Cattle Creek catchment is irrigated sugarcane along the eastern bank.

Since 1988, data from an existing network of groundwater observation bores has indicated that some areas in the Cattle Creek catchment had rising groundwater. This has led to waterlogging and salinity with conductivity measurements.

Soil type assessment is critical under these conditions as the introduction of salt by irrigation waters will increase the sodicity of the soil.  Vulnerable soils will be subject to sodium (Na) replacing plant nutrients calcium (Ca) and magnesium (Mg) on the clay particles present in the soil, thereby reducing soil nutrient levels.

Additionally, when water (even freshwater) is added to this sodic clay, the clay breaks apart and moves down the soil profile effectively reducing the drainage of the soil and again decreasing crop/plant health.

In the Arriga Plains area of the Cattle Creek catchment, the majority of the soils present are subject to waterlogging, are at risk of high salinity and are moderately to strongly sodic.

However, the lack of detailed soil type assessment and lack of well-publicised water quality monitoring throughout the region has meant that many growers continue to practice irrigation strategies that may cause long-term degradation to their primary asset.

Mitchell River’s Project Officer, Brian Prove, has been talking with some of the key people in the area to gain a better understanding. One of these people is Bronwyn Dwyer, Manager at Tablelands Canegrowers. Bronwyn has a good news story: through a combination of improved irrigation and other factors, yields in the Arriga Plains have remained commercially viable over the past 20 years.

Given the area’s importance for local producers, there is considerable interest in understanding more about how salinity and waterlogging are being managed.