Farmer: Wade Bidstrup Location: Queensland, Australia Field Area: 117 ha or 289 acres Irrigation Method: No Irrigation. Dryland/Rainfed Crops: Mungbean / Corn / Wheat / Chickpeas
"We've had about 12" of rain and water has been flowing through that paddock we OptiSurfaced, but it is draining brilliantly. You can't believe how much better it is!"
The problem in Wade's words:
I can lose half my crop to ponding in wet years.
Figure 1. Foreground showing drainage problems in this field and background showing and OptiSurface field with no standing water.
In more detail, this is how Wade explained the problem in the photo above.
In the foreground you'll see there is a field with mungbeans in it, of which the 200m or so at the end of the field have been drowned out by the water that is still lying there. If you look across to the right of the photo you can see some corn stubble. Where this corn stubble ends is where the paddock of mungbeans also ends. The mungbean paddock and paddock with the corn stubble in it has not been Optisurfaced. There is a straight line along this boundary where the water lays in the foreground and where it is not laying in the background. The paddocks in the background used to be an extension of those in the foreground, except to say that water used to lay even worse than the background paddocks than the end of the paddocks in the foreground.
Prior to the fields in the background being Optisurfaced you would have seen water laying in the field starting where it is in the mungbeans and extending probably 3/4 of the way to the trees at the very end of the photo. It would have stayed like that for weeks after this photo this taken. I can lose half my crop to ponding in wet years. Needless to say I was ecstatic to see zero water laying in the field I Optisurfaced, especially when I had this direct comparison with the mungbean field.
The Drainage Analysis shown in Figure 2 below fills all depressions in the field and then calculates the flow path based on the Existing Topography. The analysis was calculated with small furrows and beds 50 mm (2 in) high on a bearing of 188° from north or parallel to the east boundary.
The small furrows represent the micro beds and furrows created by machinery traffic and planters which dramatically affect surface drainage on low sloping fields like this one.
Based on surveyed topography and the assumption of micro furrows/beds, it shows 46% of the field or (54.2 hectares or 133.9 acres) would experience standing water.
Figure 2. Existing Topography (left) and Existing Drainage Analysis (right). Drag white slider left or right to view each.
In 2012, the yield loss was estimated at $600/ha, translating to about $70,000 loss for the whole field.
Overlaying the Ponding Map with the Yield Map produces a remarkable resemblance in Figure 3. The gaps in yield map show no yield, the red area show low yield while the green area show the higher yielding areas.
The high correlation between the low/zero yielding areas and the worst ponding areas is obvious.
Figure 3. Existing Drainage Analysis (left) and Yield Map (right). Drag white slider left or right to view each.
An OptiSurface 2Way design was generated for the field with a grades of 0.05% to 0.50% promote drainage. A smoothing of 100 m/% was also applied to promote more uniform infiltration of rainfall. The planting direction was also changed to follow the direction of the north boundary instead of the east boundary. The Proposed Topography and Cut/Fill Map are shown below.
Figure 4. Existing Topography (left) and Proposed Topography (right). Drag white slider left or right to view each.
Figure 5. Proposed Cut/Fill Map
Earthworks Volume of Cut: 11,010 m3 or 14,400 yd Volume Of Fill: 9,270 m3 or 12,125 yd3 Average Cut Depth: 17 mm or 0.67 in Average Fill Depth: 18 mm or 0.71 in
Average Cut per Area: 94 m3/ha or 50 yd3/acre
Cost $250/ha for 117 ha = $29,250 ~ $30,000
Based on the earthworks cost of $30,000 and the benefit of $70,000 in wet years the Return On Investment (ROI) is 233%.
This is another example why we believe OptiSurfacing your fields is often the highest ROI farm improvement farmers can do.