Graduate student examines impacts of sod-based rotation

Kaile Zhang, a soil and water sciences doctoral student at the UF/IFAS North Florida REC, is studying sod-based rotation (SBR) systems. Under SBR, perennial grass (bahiagrass) is part of a traditional cotton-peanut rotation. Specifically, Zhang wants to understand the dynamics of soil biota, such as bacteria, fungi, and nematodes. He is examining their interaction and the mechanisms they perform in the soil in response to different types of rotation systems. His research questions are:

  1. If we integrate bahiagrass into the conventional peanut-cotton rotation system, could the diversity and community of soil microbes be altered and subsequently benefit crops to tolerate environmental stress and management practices, as well as increase yields?
  2. If so, what are these microbes, and what microbial-mediated mechanisms regulate such benefits?

Kaile Zhang grew up in China and was around agriculture at a young age. His grandparents farmed several acres of rice each year.

“I remember when I was in primary school, my grandparents would ask relatives to help them plant, fertilize, and harvest the rice,” Zhang said. “Normally, I was there to watch them how to work or try to plant rice for fun.”

While he couldn’t help much back then, Kaile is working to help farmers increase their yields and boost soil health. He is studying sod-based rotation (SBR) systems. The SBR system is planting bahiagrass for two years, rotating to peanuts for a year, then cotton the next year. You then go back to bahiagrass.

“My research aims to understand how long-term SBR affects microbial-triggered soil nutrient cycling and crop productivity,” Zhang explained.

man standing next to geoprobe in farm field
Kaile Zhang with the Geoprobe used to collect deep soils at his SBR field, North Florida Research and Education Center. (photo provided)

Kaile authored a review paper with his advisor, Dr. Sunny Liao, and co-advisor, Dr. Gabriel Maltais-Landry, which found that temporal crop diversity enhances primary productivity.

“Crop rotation can stimulate above and below ground interactions. This affects carbon allocation, rhizodeposition, and the growth of rhizome microbiome,” Zhang explained. “Stronger above-belowground interactions will intensify ecological connections between microbial and faunal interactions among roots, rhizosphere, and bulk soil.”

He has another journal article in review based on his dissertation research. From a three-year cotton-root microbiome study, Kaile found that sod-based rotation mainly increased the cotton-root fungal diversity. The rotation assembled more beneficial microbial communities in cotton roots.

“These beneficial microbial communities are positively correlated to cotton yield across the three years,” Zhang said. “So, overall, these studies can improve our understanding of the microbial mechanisms in terms of how SBR can increase cash crop yield.”

While the results indicate SBR can increase yields, there is a question of economics.

man in laboratory examining soil.
Kaile Zhang examines soil collected from a
rhizobox at the North Florida REC.
(photo by Sunny Liao)

“We used a two-year bahiagrass rotation, but this may be unacceptable for the farmer. Basically, two years without growing a cotton or peanut cash crop. But you can use bahiagrass as hay or feed for cattle, so it could balance out. It depends on the specific context,” Zhang said. “From an ecological standpoint, it’s beneficial for farmers to grow bahiagrass for a year because it improves soil health.”

The Southern Sustainable Agriculture Research and Education program (SSARE) within the USDA has taken notice of his work. In 2020, Kaile developed a research proposal on SBR, focused on beneficial microbes, specifically the fungi Mortierella. He wanted to know how it regulates nitrogen transformations from the soil to the plant. SSARE is supporting two years of field research on this topic.

“Their recognition of my research and my hard work definitely motivated me to keep going on and study further in this area,” he said.

Kaile also credits his advisors’ support for keeping his research on track.

“All researchers face difficulties in academic life, such as performing experiments, data analysis, and writing manuscripts. When I encounter problems and it’s difficult to solve them by myself, I always discuss them with Sunny or Gabriel,” Zhang said. “They are always happy to help me address those difficulties.”


Dr. Sunny Liao, assistant professor of soil microbial ecology, calls Kaile a high-achieving student with a great passion for science.

“I am pleased to find that through his Ph.D. work, Kaile has grown from a junior scientist to a microbiologist,” Liao added. “It is enjoyable to find Kaile collecting hundreds of his baby fungi from his field sites. He gets excited very easily by discovering the mysterious pigments produced from some of his baby isolates and the potential ability of some to use these metabolites/enzymes they produce to change soil chemistry.”

Dr. Gabriel Maltais-Landry is an assistant professor of sustainable nutrient management systems. He believes Kaile’s work is providing a better idea of what microbes are present in sod-based rotation systems relative to traditional cotton-peanut systems, and what those microbes do.

“We have several years of data showing that SBR increases yields and can lead to other soil benefits, but the role soil microbes play in driving these benefits remained unclear,” Maltais-Landry added. “Linking microbial communities to function is certainly among the topics of greatest interest in agricultural sciences, and Kaile’s work is providing really useful information on that. We won’t have all the answers by the time he graduates, but it’ll be a good start to help us better understand the role microbes play in these systems, and how we can manage them to maximize benefits.”

“Soil microbes are so mysterious,” Zhang said. “They are so tiny that we cannot see them with just our eyes, but they can drive a variety of soil functions, such as driving nutrient cycling, helping the soil and plants improve stress tolerance, etc. This is amazing and compelling!”


Posted: December 20, 2021

Category: AGRICULTURE, UF/IFAS Research
Tags: Gabriel Maltais-Landry, Kaile Zhang, Sod-Based Rotation, Soil And Water Sciences, Soil And Water Sciences Department, Sunny Liao

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