Considerations Following a Wet Year

Gordon Johnson, Extension Fruit & Vegetable Specialist; gcjohn@udel.edu

From the spring of 2009 through the winter of 2010, we received record amounts of precipitation. The following are some considerations for vegetable production following a wet year.

● Check your pHs. The pH of soils during wet years often drops more than in normal periods. Be most concerned where fields have a “borderline” overall pH in the 5.7-6.0 range. Often there will be areas in those fields with much lower pHs. Specifically check your sandiest areas, which leach the most, and headlands where there may be overlaps in nitrogen application (ammonium and urea fertilizers drop the pH). These areas may have spots with pHs well below 5.5. You should also check the pH of areas in the field that were wet or waterlogged. Wet field areas initially drop in pH due to fermentation of organic matter by microorganisms in anaerobic conditions as well as an increase in carbon dioxide dissolved in the soil water forming a weak acid. However, the pH may subsequently rise in flooded soils due to reducing bacteria which consume the acidifying hydrogen. When these areas dry out, they may drop in pH again due to several soil processes. Therefore it is hard to predict the pH of wet areas and separate samples should be taken after they have drained.

● Take time to note and mark out drainage problems and take measures to address them. Drainage problems in fields can have severe impacts on vegetable crops through waterlogging that limits oxygen for roots and through increased activity of soil borne pathogens that thrive in wet conditions. This past year offered the “worst case scenario” and drainage issues are obvious. Use this information for planning purposes.

● Nitrogen carryover this year is minimal and should not be counted on. Fields with no cover crops or poor stands of cover crops will provide very little recycling. Nitrogen recommendations will have to be modified accordingly.

● Compaction from a number of sources is evident in many fields. In particular, rutted areas from field crop harvest operations last fall will need to be addressed with targeted tillage this spring.

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