Adapted from the Spring 2016 edition of the Sunburst Quantum Yield Newsletter
This spring will be characterized by unusually cool weather. Several days are anticipated to be laden with freezing to near freezing temperatures. Our experience with various species of plants, including trees, vines and vegetables, indicates that the degree of negative impact by temperature extremes is greatly buffered in plants hosting superior physical integrity and physiological efficiency.
For example, tomato plants of the Rutgers variety were placed on four separate regimes:
- Control with conventional fertility (CK)
- Conventional fertility with higher nitrogen (CK+N)
- Balanced fertility (Bal)
- Balanced fertility with selective microbiology (Bal+M)
The plants were grown under greenhouse conditions for two months before subjecting the four groups to freezing temperatures of 32 degrees Fahrenheit and extreme heat conditions of 115 degrees Fahrenheit. Plants were rated on a 0 to 5 scale, with 0 representing wilt and collapse, and 5 representing unaffected status. Following are the summary of those test results:
Freezing Temperature Exposure
Extreme Heat Exposure
Note: Means followed by different letters are statistically different with a minimum 95% confidence level (for example, 0.5 a and 0 a are not statistically different, while 3.5 b and 4.8 c are statistically different).
Additionally, these same four groups of plants were subjected to high pathogen inoculum levels of Verticillium dahliae microsclerotia (350/gr soil) and grown for two additional months. The results of this test were as follows:
A Deeper Understanding of These Weather and Disease Resistance Experiments
The tests provide a firm model for overcoming either pathogenic or physiologically induced stress. Plants that were grown on both the “balanced” and “balanced + select microbiology” regimes hosted between 27% (Bal) and up to 36% (Bal+M) higher tissue density over that of the conventional check (CK). Further, it is a well understood principle that the level of photosynthetic harvest has a near linear relationship with leaf tissue density. That is, the denser the leaves, the more carbon and energy that is harvested within the given time period.
Differences in CO2 harvest between CK vs Bal+M, for example, were approximately 28 mg CO2/dm2/hr for the CK vs 45 mg CO2/dm2/hr for the Bal+M. This represents no less than a 161% increase in photosynthesis. It is also a common understanding in plant physiology that the more efficient the photosynthesis, the more efficient the overall physiological machinery of the plant proper. For example, we have seen time and again that the basic physiological delineation between a susceptible versus resistant plant resides in the rapidity with which a resistant plant responds to pathogen induced that of the susceptible plant. This is what I mean when making the statement that, “Resistance Is A Rate-Related Phenomenon.”
Takeaway from the Experiment
Elsewhere, we have touched upon the physics of “relative mineral harvest” from the soil. While nitrogen is harvested with ease, phosphorus, potassium, calcium, magnesium, and other minor elements are taken up with greater difficulty. Going into spring weather, the soil temperatures are still below 60 degrees Fahrenheit. Thus, harvest of the others is made even more difficult. It is imperative that balanced nutrition and not a skewed nitrogen nutrition reach emerging and developing growth. This is not only in light of previously mentioned resistance to various stresses, but also in relation to energy dynamics associated with nitrogen assimilation (>8,200 Kcal per #N).
Thus, careful incrementation of balanced minerals is the rule. Superimpose on this, selective microbial activation of the soil and you will gain greater control of the applied, balanced minerals. For microbe activation not only places nitrogen into a controlled-release form, but minimizes its leaching and further facilitates the timely release of the others. The essence of selective microbial activation resides in proliferating the indigenously adapted beneficial microorganisms. Thus, a selective, readily assimilatable substrate that is preferentially metabolized by beneficial microbiota is most effective. In most cases supplementation with preferred strains acts merely as ensured antagonism against the chance proliferation of pathogens.