Over the past few years, researchers have extensively studied biochar as a phosphate fertilizer alternative. Biochar is a recyclate produced by burning organic feedstocks without oxygen at high temperatures. The sources of biochar can vary significantly, ranging from waste wood to chicken manure or leaves.
However, previous studies have shown that plants responded differently to biochars, with some growing better, others showing no response, and some even being harmed by the biochar fertilizer.
An interdisciplinary team of researchers from the Joseph Gottlieb Kölreuter Institute for Plant Sciences (JKIP) and the Institute for Technical Chemistry conducted an experiment using tomato seedlings. They discovered that the origin of the biochar biomass played a crucial role in its symbiosis with arbuscular mycorrhizal fungi (AM fungi) present in the soil.
In their first experiment, the team compared the effects of biochars made from wheat straw and chicken manure. The chicken manure biochar contained nine times more phosphate than the wheat straw-based biochar, which is a crucial nutrient for plant growth. Tomato seedlings fertilized with chicken manure biochar showed excellent and rapid growth due to the abundant available phosphate. Professor Natalia Requena, an expert in molecular phytopathology at JKIP, expressed these findings.
Symbiosis with AM fungi ensures long-term growth of the plant
In a follow-up experiment, the researchers focused on introducing AM fungi to the tomato plants. These microfungi have been present on Earth for over 400 million years, residing in the roots of about 80% of land plants. Their role involves colonizing the plant's roots, absorbing phosphate, and transferring it to the plant. In return, the plant provides them with essential nutrients like sugars and lipids.
Upon studying specific molecules, the researchers made a remarkable discovery: the phosphate-rich biochar derived from chicken manure hindered the symbiotic relationship between tomatoes and AM fungi. Molecular exchange between them was significantly reduced. On the other hand, the wheat straw-based biochar had the opposite effect, fostering an active and healthy symbiosis between the plant and microfungi. Professor Natalia Requena highlighted that plants fertilized with wheat straw biochar exhibited enhanced compatibility with other microorganisms and better protection against pathogens. The complexity of the plant's molecular response in this context was unexpected.
Understanding the cells better, fertilizing less
To validate their findings, the research team utilized gene expression analysis, a complex and costly method that allows them to examine the plant's genes and identify which markers are activated or suppressed. Professor Natalia Requena emphasized the significance of this approach in gaining insights into plant responses.
The team acknowledges that further experiments will be necessary to gain a deeper understanding of plant behavior. Unlocking this knowledge will eventually lead to the ability to program plants for reduced phosphate requirements, thereby reducing their dependence on mineral fertilizers. This potential achievement highlights the importance of ongoing research in sustainable agriculture and resource-efficient plant growth.