A friend sent me a fascinating article from Acres U.S.A. magazine. It focuses on the early work of soil scientist Henrik Lundegårdh (pronounced Lun-de-gourd) who, in the 1920s, established an essential framework for understanding the biology of crop productivity. The majority of the content of this newsletter comes directly from the article.
Lundegårdh was concerned about the early rush into inorganic chemical farming based on the new discoveries of mineral plant nutrition. In his view, soil biological functioning should be part of routine soil fertility assessment. He selected as his main indicator soil CO2 respiration since it reveals the all-inclusive metabolic activities of soil bacteria, fungi, arthropods and plant roots. He labeled this indicator “the CO2 factor.” Lundegårdh already grasped the significance of the global carbon cycle, but more importantly, saw an enormous upside to CO2 in the context of quantifying “healthy soils.”
The essence of the discovery is that plants obtain the CO2 they need not from the atmosphere, per se, but from soil respiration. Lundegårdh showed that if soil respiration fails to furnish a sufficient quantity of CO2, the supply from the atmosphere is furnished too slowly to prevent a CO2 deficit in the leaves, and thus a partial starving occurs. This can be intuitively grasped as a basis of truly biological-oriented farming.
Lundegårdh outlined the biological pathways that directly contribute to crop productivity, including:
- mineralization of organic nitrogen to nitrates (due to microbial activity);
- extraction and buffering of the soil solution (due to dissolved carbonic acid from microbial activity);
- soil aggregate formation (due to microbial activity) and;
- furnishing plants with CO2 for photosynthetic assimilation, also due to soil respiration.
The implications of Lundegårdh’s discoveries were largely ignored yet he was a pioneer showing that we cannot separate living soil from high-yielding crops.
Underlying this is the age-old axiom that you can’t manage what you cannot measure. Private soil labs have adopted a new type of soil test called Solvita, that measures soil CO2 respiration. Solvita has a website showing its labs across the U.S.
The inescapable conclusion is that soil degradation — despite our best efforts — is likely to continue unabated. Aside from erosion and salinization, the central crisis is depletion of soil biological capital, or Lundegårdh’s “CO2 factor.” In fact, it is possible that we are approaching, for the first time, a new low-water mark in soil fertility, for which Lundegårdh’s studies are a harbinger and warning. We need to add new testing tools, so soil health can be measured, compared and given priority.
Speaking of healthy soils, please strongly consider postharvest applications as an investment in your soil biological capital and next season’s crop. As always, I’m happy to talk to you about our products and recommendations.