Reducing yield losses from waterlogging

Introduction

A large portion of the broad acre farmers in Australia utilise GPS guidance in some form. Those using RTK GPS, either with their own private base station or a local base from their service provider, have the ability to collect data with the same accuracy as surveyors. Often elevation information for entire farming operations is clogging up data cards. This information is the key to reduced waterlogging, higher yield and increased productivity.

Data collection

Elevation data can be collected during a normal field operation provided the following criteria are met:

1. RTK GPS (±2cm) is used with the base no more than 10km away
2. Machine speed is below 20km/h
3. Not a heavy tillage operation
4. Not an operation where guided machine weight will vary greatly (avoid spraying data)
5. Swath widths are less than 24m

Most GPS guidance systems will facilitate collection of data and export in a fairly generic format. Retrieving data will generally involve inserting a USB stick into the guidance screen, or removing a flash card and extracting data using a card reader.

Data analysis

A number of software packages are available to allow user upload and view data collected during field operations. Some allow more comprehensive analysis of the elevation data including:

• Depression/slope analysis
• Comparison of slope/depressions with yield data
• Runoff modelling
• Contour Bank/Adaptive Curve Drain design

These tools, or consultants offering these services, can identify the areas where treatment is required, evaluate a number of treatments and provide a cost effective solution.

GPS land levelling

GPS control of levelling equipment allows control of the machine height at a known location. It facilitates the construction of surface designs that include a multitude of slopes, flow directions and earthworks balance zones. In short if it can be draw up on a computer, with GPS machine control it can be built.

A typical earthworks comparison is tabled below. Details are for a 40 hectare dryland field with significant drainage issues. It was desired to have all drainage with the row direction and no in-field drains.

The ability of the GPS controlled machine to work with suitable existing topography and only move dirt where it is necessary results in a significant reduction of the volume of earthworks. This reduces the cost of the proposed works, and also reduces the damage to the field with a reduction in heavy cuts, reduced construction traffic and reduced compaction. Coupled with a targeted approach developed in the data analysis stage the detrimental impact on the field area can be minimised.

Software programs are available to prepare machine control files for a number of drainage solutions. These solutions include:

• Single plane field areas (as built with laser equipment)
• Multiple slope designs where slope parameters are maintained with drainage:
  • in one direction (down slope)
  • in two directions (along rows but to either end of field)
  • in four directions (to any edge of the field)
• Channels and deeper gully repairs

• Embankments and diversion works

GPS guided drainage solutions

The combination of GPS elevation data, software analysis and “adaptive curve” guidance enables the design and implementation of fixed grade drainage lines in fields. These lines have a consistent slope to facilitate controlled drainage of field areas away from existing gullies and machine wheel tracks. Constructing these drains/banks with consistent slope reduces erosion and ensures drainage of fields without some of the water retention problems associated with older style contour banks.

The “adaptive curve drain” concept utilises this path of consistent slope to construct shallow drains throughout the field. These drains are constructed in three passes with a grader and are designed to be easily trafficable, but intercept and divert water flowing along wheel tracks. These “adaptive curve drains” are similar to a small contour bank, with the consistent slope providing improved drainage capability. The GPS guidance and collected elevation data allow ease of construction and ensure that the drains have consistent slope without moving large quantities of dirt.

Other work being carried out with GPS elevation data and machine control include:

• Construction of bankless channel irrigation systems including channels, drains and roads
• Construction of constant head rotabuck areas for syphon irrigation whilst minimising field disturbance
• Design and installation of plantation row alignments within desired slope parameters

Conclusion

Many farmers are already equipped with the tools to identify and plan for remediation of drainage issues. GPS guidance and machine control facilitate smarter solutions to age old problems of erosion and drainage. Potential solutions can be prepared, costed, evaluated and if feasible, implemented at the right stage in crop rotations.

Contact details

Bernie Martin
Tahlee Consulting Services
Ph: 0428 437 982
Fx: 02 6145 2085
Email: bernie@tahlee.com.au