The following is an addition to the post from August 2 concerning a case of yellowing strawberry plants in a field in Castroville.  To summarize, we concluded that the plants are turning yellow because they are being poisoned by excess amounts of sodium and chloride accumulating in the bed.

So of course, and indeed the question was asked right away, what can we do about this problem?  The three points below are a start:

1.  The dramatic accumulation of sodium and chloride at the surface of the bed in this study indicate that these are not being adequately leached, which was verified by our observation of soil saturation at depths below the bed.  If this is correct, by increasing drainage we will be able to ameliorate the situation and restore a normal leaching pattern.  Short of installing a system of subsurface drainage, there has been some anecdotal evidence of success in using a certain “Yeoman’s plough” which is essentially a shank going some 16 inches deep into the soil next to the bed opening a deep cut in the soil improving aeration and water infiltration.   This has not been tested in replicated trials however, so I can’t make a firm recommendation of this method at this time.

2.  We have every indication in this study that substantial amounts of calcium are precipitating out as lime, and is therefore not replacing exchangeable sodium.  We could reduce the amount of precipitation of calcium (increasing the exchangeable calcium) by acidifying the irrigation water which would go some lengths to mitigate the sodium hazard (SAR).

3.  Finally, there are other useful steps which can be taken to reduce the amount of sodium and chloride being introduced into the field.  For example, a grower experiencing a situation of high sodium and chloride should avoid using sodium nitrate or potassium chloride fertilizers.