Microbial characterization of fields planted with the perennial crop Kernza® (Thinopyrum intermedium) and the annual crop Spring barley (Hordeum vulgare)

Abstract

The terrestrial ecosystem stores up to 2400Gt of carbon in the upper 1m of the soil profile.
However, this carbon storage is not stable and is vulnerable to loss. Agricultural soils with continuous heavy management drive a release of this soil carbon to the atmosphere. Recently, the implementation of perennial crops has been suggested as a method to facilitate a greater carbon sequestration. However, the mechanisms of what happens with the soil microorganisms in a perennial crop compared to an annual crop have been sparsely studied. This study investigated the microbial activity in soils from a field planted with the perennial intermediate wheatgrass (IWG) commonly known for the name of its grain Kernza® (Thinopyrum intermedium) and compared it to the microbial activity in soil planted with the annual crop spring barley (Hordeum vulgare) from autumn to spring.
The microbial activity was measured by tracing radioactive leucine incorporation into bacterial proteins and acetate incorporation into fungal ergosterol. Respiration in the soils were measured, including substrate induced respiration (SIR) to obtain an estimation of the biomass found in the soils. By including a microfluidic chip design with four different structural complexities imitating soil pores, the microbial peptidase activity and fungal hyphae numbers can be investigated, as well as implementing a deep learning code to obtain numbers of bacteria found as well as the size of the bacteria.
Analysing the soils’ microbial activtiy with different methodologies, aids a greater understanding of what happens in the ground under different crops.
Results found that the microbes in the kernza soil had a higher microbial activity when measuring bacterial growth with leucine incorporation and enzymatic activity by the microfluidic chips. Bacterial numbers and size were larger in the kernza soils, as well as a higher number of fungal hyphae. A higher complexity in the microfluidics increased the enzymatic activity for both crop types, as well as the number of bacteria.
Seasonal patterns were inconsistent for the different methods.
Overall, the soils under the kernza crop had a higher CUE, suggesting that the microbes in the fields with kernza allocates more carbon to the soil than the microbes in the soils under spring barley.

Popular Abstract

The activity of soil microbes under a perennial vs. an annual crop

Underneath the crops that are used for flour and other type of grains one might use daily, there are millions of microorganisms making sure that these crops get the nutrients they need. These microorganisms are decomposing organic material enabling the crops to grow. However, these microorganisms might be affected by the type of crop planted in the soil.

In the most common agriculture practices, the annual crop is planted and harvested every year, often leaving the soil bare over winter. In preparation for planting a new crop, the soil is heavily managed, often leading to the loss of carbon from soil into the atmosphere. Many actions towards reducing the release of carbon into the atmosphere are important if the atmospheric CO2 levels are to decrease. Soils have a great possibility to store carbon, more than what are already found in the soil, so in effort to increase the soil organic carbon in agriculture, farmers have started implementing perennial crops into the growing schedule.

The first commercially available perennial crop is the crop Kernza® developed from the intermediate wheatgrass (Thinopyrum intermedium) (IWG). Kernza grows deeper roots than an annual crop and has shown to increase the microbes found in the soils, which in turn could increase the carbon fixated into the soil via microbes. What I sought out to do, was to investigate how the microbial activity in soil planted with the perennial Kernza and the annual Spring barley differed. To do this I implemented two different methodologies, with the idea of getting a wider picture of how microbes differed in the soil.

Is Kernza “the better crop”?
My results showed that the microbes were more active in the Kernza soils, and more biomass was measured in Kernza soils as well. Soils sampled at different times of the year influenced the microbial activity differently depending on what microbe was measured. Depending on the method, the activity and biomass found in the soils at different time points varied and had no consistent trend. Future studies focusing on the difference in microbial activity between soils planted with a perennial crop and an annual crop are needed to understand if the change is reoccurring at different sites with different soil types.

Even though two different methodologies were used for the results obtained in this study, a common thread of a higher activity of microbes was found in the Kernza soils, with a higher carbon use efficiency in the Kernza soils. Whether this higher microbial activity and carbon use efficiency leads to more carbon stored in the soil needs to be researched further.


Master’s Degree Project in Biology 45 credits 2024
Department of Biology, Lund University

Advisor: Lettice C. Hicks and Edith Hammer, Functional ecology; Johannes Albertsson SLU Alnarp

• author: Pinholt, Frida
• supervisor: Lettice Hicks; Edith Hammer
• organization: Degree Projects in Biology
• course: BION02 20232
• year: 2024
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 9178927
• date added to LUP: 2024-12-19 11:55:26
• date last changed: 2024-12-19 11:55:26