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Progress Update: Using an EM38 for moisture measurement at Black Earth Agronomy

EM38 Blackearth.com.au

Over the last few years, we have been engaging in extensive trials using an electromagnetic device called an EM38 to measure moisture levels in the soils around Cecil Plains, Norwin and Brookstead. After working with Jenny Foley in collaboration with the DNRM as part of the CRDC funded project NRM1401, I believe we are finally reaching the point where our results are accurate and reliable enough to assist with decision making.

I’ll elaborate in another article as to how we have achieved this but in this article I will discuss the potential uses and applications for this technology.

In the Fallow

One application that I am sure everyone will be interested in is that of fallow moisture measurement. After soil calibration, Black Earth Agronomy should be able to walk into any section of a field and quickly ascertain plant available moisture levels for depths 0 - 75cm and 0 - 150cm. This means that it will no longer be necessary to run around a field with a push probe making rough guesses as to the underlying moisture.

Another application in fallow fields may be to use the EM38 along with APSIM modelling software (CSIRO) to determine potential yields for a range of crops under a variety of possible seasonal weather conditions. This would enable us to determine whether it was better to plant immediately or leave the field fallow until sufficient moisture has been accumulated in the soil profile to achieve a target yield. We could also use potential yield data along with gross profit margins to find the most valuable and viable cropping options for that part of ground at that particular time.

Irrigations Scheduling

The EM38 is going to be particularly useful for deciding when to irrigate. The EM38 can give us accurate information about a field's overall moisture deficit allowing us to anticipate and act upon deficits in a similar way to what we already do with the Neutron probe. Unlike the Neutron probe, the EM38 allows us to measure anywhere in the field because an access tube is not necessary. If a particular measurement location does not appear to be representative of the field, we can easily adjust that location.

Infield water use

Another potential use of the EM38 is to measure moisture levels before and then directly after irrigation to determine exactly how much water was actually applied to the field. This would not only allow you to determine your $/L but would also allow you to determine what water losses are occurring between the dam and the field.

Soil Variability Mapping

Soil variability and salinity mapping using the EM38 has been extensively used in other regions and could find some use in some circumstances on the Darling Downs. At this time we don’t have the software and equipment to accomplish this but this could change based on interest levels.

Other more speculative uses

There are a number of other potential uses that have not been fully tested at this stage.

One such use would be to determine the length of water logging events in different parts of the field and then using this information to limit water logging in future irrigation events.

Another potential use is to measure compaction within a field. This would allow us to measure the impact of different forms of traffic of the field so as to limit compaction in the future.

Conclusion

The soil calibrations for the EM38 should be up and running by the upcoming 2016-17 summer cropping season which means that many of these applications above will be available for use. If anyone would like a demonstration of the EM38 or would like to discuss possible uses on your farm please feel free to contact me on 0428 615 711 or at blackearth@blackearth.com.au.

Written by Robert Boulton

 

The information provided above is based on experience and knowledge developed while operating as an Agronomist on the Darling Downs. The opinions contained within this post are entirely that, and may not apply to a grower's specific circumstance.  We recommend consulting your own agronomist to ensure best performance on your own farm.

 

 

The Cluster Caterpillar (Spodoptera Litura) are another of those occasional pests on the Downs that are capable of impacting a variety of different common broad acre and vegetable crops. They tend to be more prevalent in coastal and tropical regions and can cause significant damage in these districts. Their presence in the Ord in Western Australia contributed to the failure of cotton in the region from 1964 to 1974.[1]

The eggs are often laid in a crowd together and small larvae can often be found bunched on the same region of a leaf. This behaviour leads to their common name of Cluster Caterpillar. The larger adults are very easy to identify with dark triangles running down the top sides of the body. The following short video was taken in the field and shows these markings in detail.

Here is another showing a large Spodoptera's typical movement pattern.

Smaller ones can be identified by two dark patches on ‘shoulders’ behind the head. The video below was taken in the field near Nangwee and shows the ‘shoulder’ patches and the movement typical of a Spodoptera.

This video shows them at first instar.

This website has some incredibly detailed photos of Spodoptera that should help anyone with identification.

Control of Spodoptera can be necessary in bean crops during the vegetative stages where defoliation (>30%) is severe enough to impact yield. Flowering and podding stages of a crop are more vulnerable to defoliation and so should draw treatment when defoliation approaches 15-20%.[2] There may also be some risk to flowering points and pods so these should also be monitored for damage.

I’ve only had limited experience of Spodoptera Litura in Cotton and Soybean on the Darling Downs but Black Earth’s other operating area in the Burdekin regularly deals with it as a pest. It does appear to have some capacity to deal with the Bollgard II Bt genes at certain times of the year as I have occasionally found large specimens on cotton leaves in fields with no weeds. DAF Qld’s website does indicate that Bacillus thuringiensis (Bt) only controls them when they are small. Another interesting point to note is that they cannot be controlled with NPV's such as Vivus Max or Gemstar.

Written by

Robert Boulton

[1] https://www.agric.wa.gov.au/cotton/cotton-ord-river-irrigation-area

[2] https://www.daf.qld.gov.au/plants/field-crops-and-pastures/broadacre-field-crops/integrated-pest-management/a-z-insect-pest-list/cluster-caterpillar

The information provided above is based on experience and knowledge developed while operating as an Agronomist on the Darling Downs. The opinions contained within this post are entirely that, and may not apply to a grower's specific circumstance.  We recommend consulting your own agronomist to ensure best performance on your own farm.

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