Drought conditions, heat stress, heavy frost and freezes all dramatically impact our crops. In California, over the Labor Day weekend, we witnessed a heat wave with temperatures soaring as high as 117 degrees in wine growing regions like the Santa Cruz Mountains. Many winemakers experienced a gut reaction of fear, especially with sensitive varieties like Chardonnay and Pinot Noir.
Frankly, the same heat wave and the lack of cooling night time temperatures hammered crops across California and we saw the impact on our fruit at harvest. In many cases the fruit wasn’t as firm, bright, consistent, etc. as we would expect and in some areas and crops, yields were down across the board. Growers have been asking me if there is something we can do to mitigate weather related plant stress.
We know that water stress can affect soil chemical, physical, and biological activities that are essential for plant and soil health. As soil moisture declines so does nutrient uptake as water is the major medium for moving nutrients so irrigation practices can play a major role.
However, little attention has been paid to the soil microbial community responses to combined heat-drought stresses. Heat waves will likely alter biogeochemical cycling, because of their effects on C:N in roots, Carbon flux to soil, plant N uptake, and microbial biomass and activity. Temperature increases in the soil alters microbial activity, affects the breakdown of soil organic matter (SOM) and the release soil carbon back to the atmosphere. Since soil microbes, in general, are Carbon limited, the availability of more plant Carbon in the soil allows for expansion of their population. During heat waves, more absorption of N by plants and an expanding microbial community may cause development of nitrogen limitation for the soil microbes. Research has inferred that this might account for the reduced microbial activity in the soil during heat waves (e.g., soil respiration). It also begs the question as to whether we should be feeding our soil organic nitrogen or immediately available nitrogen during heat stress times.
The ideal situation is to have more soil organic matter (SOM), much of it in the form of Carbon, in order to be in better position to weather these periods of excessive heat and maintain microbial communities. It’s also important to note that just a 1% increase in organic matter allows the soil to retain an additional 20,000 gallons of water per acre. If there was a product on the market that provided 20,000 gallons of water storage per acre wouldn’t everyone be buying it? Andaman Ag offers a host of products to accomplish this in a cost-effective manner in a very short period of time with the longer-term goal of increasing organic matter 2-3%.