As a postscript to last week’s post regarding salt and ammonium damage to area strawberry plantings, I will outline the results of the soil samples taken from a field demonstrating the symptoms described in that article.
Steve Koike and I collected soil samples from the affected field last Thursday, January 5. Soil samples were collected from four blocks, one of which had been overhead irrigated the day previous, and consisted of composites of at least five 5” deep samples taken from around the fertilizer band by the plant roots.
Samples were immediately taken to Soil Control Lab in Watsonville for analysis.
Results are as follows:
|
|
Nitrate (ppm) |
Ammonium (ppm) |
EC (dS/m) |
|
Sample 1 (not overhead irrigated): |
58 |
4.8 |
2.8 |
|
Sample 2 (not overhead irrigated): |
72 |
5.2 |
4.2 |
|
Sample 3 (not overhead irrigated): |
69 |
4.8 |
3.8 |
|
Sample 4 (overhead irrigated): |
24 |
5.1 |
2.2 |
The results are pretty clear in showing that the block (Sample 4 ) which had been watered by overhead irrigation had three times lower nitrate concentrations and about half the EC (which is electrical conductivity, a measure of salt) of the other three averaged as a group, but more equivocal on the reduction of ammonium.
To interpret the data in the table above, we can refer to work done some time ago which demonstrated EC’s in excess of 1.0 were related to loss in yield of strawberry, suggesting that real damage could occur at the 4x levels in the table above.