Crop rotation is a common farming practice where different series of crops are planted in the same area each sequential season. Planting different crops on the same piece of land has been used since Roman times and has been proven to improve plant nutrition, benefit soil health, and control the spread of disease
A new study to be published in Nature’s ‘The ISME Journal’ reveals just how profound crop rotation’s effect is on enriching soil with bacteria, fungi and protozoa.
“Changing the crop species massively changes the content of microbes in the soil, which in turn helps the plant to acquire nutrients, regulate growth and protect itself against pests and diseases, boosting yield,” said Professor Philip Poole from the John Innes Centre.
Researchers collected soil from a field planted with wheat, oats and peas. After growing wheat, it remained largely unchanged and the microbes in it were mostly bacteria. However, growing oat and pea in the same sample caused a huge shift towards protozoa and nematode worms. Soil grown with peas was highly enriched for fungi.
“The soil around the roots was similar before and after growing wheat, but peas and oats re-set of the diversity of microbes,” said Professor Poole.
After only four weeks of growth, the soil surrounding wheat contained about 3% eukaryotes. This went up to 12-15% for oat and pea.
Every gram of soil contains over 50,000 species of bacteria so the task is enormous when analyzing DNA samples, so researchers sequenced RNA so a full snapshot can be taken of the active bacteria, fungi, protozoa and other microbes in the soil.
“By sequencing RNA, we can look at the big picture of active microbes in the soil,” said PhD student Tom Turner from the John Innes Centre. “This also allows us to work out what they are doing there, including how they might be helping the plants out.”
“Our work helps explain the experience of farmers in the field,” said Professor Poole.
The findings of the study could be used to develop plant varieties that encourage beneficial microbes in the soil. John Innes Centre scientists are already investigating the possibility of engineering cereal crops able to associate with the nitrogen-fixing bacteria normally associated with peas.
Professor Poole comments, “Scientists, breeders and farmers can make the most of these effects not only with what they grow but how they grow it.
Brown Mang Onwuka