A new study shows that crop rotation increases soil fertility just by boosting the diversity of soil microbe populations. Could that mean that ornamental mass plantings might have a long-term negative effect on soil health?
Researchers at the University of New Hampshire were able to isolate crop rotation from other factors such as variable fertilizer or pesticide inputs to determine that crop rotation alone increased soil carbon levels (an indicator of microbial activity) by around 33%. Soil nitrogen levels also increased, which means that overall both soil health and soil fertility increased with no other inputs, just rotating crops.
Researcher Lisa Tiemann says:
“The data we present are the first to support the hypothesis that increasing rotational diversity fundamentally changes microbial community structure and activity, with positive effects on aggregate formation and soil organic matter accrual. These findings provide further support for the use of rotational diversity as a viable management practice for promoting agroecosystem sustainability.”
Although these findings were from agricultural crop rotation of soy, wheat, corn, red clover and rye, I wonder whether it could also be applicable to our preference for large swathes of single species plantings, rather than biodiverse or successional plantings. Perhaps the long-term failure, and also increased pest-susceptibility of mass plantings we are seeing in Australia among lilly pillies, clivea and agapanthus can be partly attributed to a loss of soil microbial diversity from this single species dominance? A bit like we’re now learning happens in our own human gut, where a narrow diet reduces our gut flora diversity, making us more susceptible to infections and allergic responses.
More on more on ‘Crop Rotation Boosts Soil Microbes and Benefits Plant Growth’ at the University of New Hampshire.