Tone Ag Consulting Ltd. » Irrigation

Manure and Tile Drainage

jtone — Fri, 30 Apr 2010 19:26:39 +0000

Extension.org has an article up on Preferential Flow of Manure in Tile Drainage. We’ve done some work with tile drainage and plenty of work with manure application, but no projects so far that overlap the two. A lot of of the advice seems like common sense, e.g don’t apply manure when the drains are flowing. The key is to be aware of the special conditions that subsurface drainage can create in a field and to make sure both the land owner and the applicator are aware of the actions needed to mitigate those conditions.

Relating Veris Readings to Salinity

jtone — Mon, 16 Nov 2009 20:02:48 +0000

One of the challenges for irrigated potato production in Manitoba is that potatoes are quite sensitive to salinity. Mapping salinity in a field is done via Veris, which measures the electrical conductivity (EC) of the soil. Unfortunately factors such as soil moisture and soil texture can affect the Veris readings, so these readings need to be correlated to actual soil salinity readings.

We’ve tried different methods for correlating the Veris readings to the soil salinity and this is the method that’s worked the best for us so far:

Map the field with the Veris unit
Identify sites with high, moderate, and low Veris readings (at least one of each per section, if not per field)
Soil sample each site at depths of 0-6″, 6-12″, 12-24″, 24-36″, and 36-48″
Have each sample tested for cation exchange capacity (to identify changes in texture) and saturated paste extractable salt (salinity)
Correlate the soil test results with the Veris readings

Step 5 is the one I want to look at in more depth.

The Veris readings are 0-30 cm and 0-90cm. This corresponds to 0-12″ and 0-36″. What I do is take the average of the soil samples for those depths and compare them to the Veris reading. I end up with two tables (one for each Veris depth) relating the Veris reading to the averaged soil sample salinity for that depth. Then I create a XY scatter chart with Veris readings as the Y axis and soil electrical conductivity readings as the X axis. I then add a trendline and use the formula from that trendline to estimate the salinity values across the field. These estimated salinity values are then used to draw a lovely map that shows the locations of any saline spots in the field. Then can then be managed appropriately to ensure that they do not spread or affect the production of poatoes.

I’m fairly certain that my methodology as described above could be improved, so if anyone has any suggestions I would appreciate them. Thank you!

Veris Work in Manitoba

jtone — Mon, 10 Aug 2009 17:02:15 +0000

Tone Ag Consulting uses a two step process to map soil salinity. First,we use Veris to measure the electrical conductivity (EC) of the soil across the field. Then we select areas of the field with high, medium, and low EC and take soil samples. These samples are sent to a soils laboratory to measure their salinity levels. The EC reading and the soil salinity measurements are then reconciled to produce an equation which is used to convert EC to soil salinity across the field.

There is no universal EC to soil salinity conversion because factors such as soil texture and moisture can affect the EC readings. As a starting point, PFRA has found that the following are good correlations for loamy soils.

Salinity Level	EC Reading
None (0-2 dS/m)	0-75
Weak (2-4 dS/m)	76-110
Moderate (4-8 dS/m)	110-175
Strong (8+ dS/m)	>175

This electrical conductivity (EC) based on saturated soil extract is measured as deciSiemens/m or dS/m and normally ranges from less than 1 (very low salt for saturated paste method) to 10 or more on very saline soils.

A lot of our salinity work has dealt with the effects of salinity on irrigated potatoes. Potatoes have a threshold soil salinity tolerance of 1.7 dS/m, the level for which there is no loss of yield. For every increase in soil salinity of one unit of conductivity above this threshold, the yield potential decreases by 12 percent. A value approaching 4 dS/m in the soil would result in a 28% decrease in potential yield. If you are interested in the relative salt tolerance of crops grown in Manitoba, see MAFRI’s Crop response to salinity table.

If you suspect that salinity is an issue in some of your fields, give us a call and we can map out your fields and advise you on what to do to minimize its effects.