Mango production and ecosystem services

Ross Maxwell has been growing mangoes for almost 30 years and recently moved to the NT to manage Jabiru Farm at Berry Springs. I spoke to him about improving water use and pest management.

‘Quality fruit is the big driver for us, and that’s dependant on irrigation and stress. You’ve got to scare them into producing fruit, and then you give them more water. 

‘Most farms I’ve worked on have problems regulating irrigation. There are scientific papers around saying how much water you need to use, but figures vary widely. With sandier soils compared to Queensland it’s hard to know how much rain you need before you don’t irrigate. Without specific information for your farm you tend to apply more water than less.

‘Getting the right information comes down to doing empirical trials on your patch. We did a rough irrigation audit, measuring the actual output of water with jugs, and it varies throughout the farm. The trees are surviving in a broad range of irrigation regimes and they don’t seem to produce any differently.

‘Ideally, to improve water use on farms in the NT I think we need to use Enviroscan probes. After a couple of years of watching water levels on different soils and how the trees react you’ll get a picture on how to manage water.

‘A cheaper option is using three different lengths of tensiometers. They show you how quickly water travels through the soil profile and help decide how much water you really need.

‘There are other questions we need to answer, especially around the use of chemicals to control pests. I think there is scope to reduce chemical use up here compared to Queensland because there are fewer diseases. And I think we need to look more closely at integrated pest management. For example, is it a good practice to leave grass un-slashed in every second row to provide a habitat for predatory insects? Do windbreaks help reduce pests (as suggested for bacterial spot)?

‘Reducing harsh chemicals is something we should do. It’s such a big issue down south. I don’t use chlorides because I think it has a long term impact on the soil. When you kill the life in the soil you can get a bacterial dominance instead of fungi which is what you need for trees. Production drops off so you start using more fertiliser. That’s not sustainable.

‘I use potassium sulphate instead, which is more expensive but a softer option and better for the soil in the long term. And of course better soils mean better water penetration and less water use. Everything ties in.’