45th Seminar Series with Janina Dierks on ” Plant-soil interactions for sustainable crop production”
Welcome everyone to my talk on leveraging the interactions between plants and soil for sustainable Crop Production first I will share with you my overarching research goal and my motivation behind it then to become more concrete I will tell you about some of my previous research and after that I will provide
Some insight into what my PhD students are currently planning to work on these coming years so I think we all agree that one of the pressing Global challenges is to figure out how to meet the increasing demand for food while reducing the negative environment footprint of Agriculture and further I think we agree
That there are different directions from which to approach this question agriculture occupies almost 40% of the Earth’s icree terrestrial surface and this m shows the world’s crop BLS yield that is gained relative to the potential y that yield that could be achieved in any given area the yellow
Shows High yielding areas and the orange and red show areas where yields could potentially be much higher than they currently are in subsaharan Africa you see that there are extensive areas where yields could be much higher than they currently are and this might be due to various
Factors one of them being that the majority of farmers in subsaharan Africa lacks access to sufficient external inputs such as fertiliz and pesticides this map also nicely illustrates that croplands in Western Europe and North America are mostly High yielding in these areas external inputs tend to be highly used and while
Allowing to generate high yields it comes at a high environmental cost agriculture accounts for 25% of all greenhouse gas emissions worldwide it is responsible for the loading of nutrients especially nitr and phosphorus into the biosphere and pollution and agriculture is the single largest cause of biodiversity loss further agriculture consumes 70 to 90%
Of all fresh water that is used by humans and yet there are 800 million people hungry worldwide so if we are to help achieve the United Nations sustainable development goals such as zero hunger and life on land the challenges to find a way to increase and or maintain years without
Extensive use of external inputs what could provide at least part of the solution what could enhance the sustainability of crop production across farming systems worldwide is if we better understood how to best harness ecological processes so leveraging ecological processes and specifically the interactions between plants and soil abiotic and biotic
Variables to help achieve sustainable AC ecosystems forms the foundation to my research approach it’s the direction that I have been and intend to continue taking to address the global challenge of meeting the increasing demand for food while reducing the negative environment footprint of Agriculture my research approach is
Twofold one I take our fundament knowledge gained from small scale experiments into the field to enhance our mechanistic understanding of plant so interactions in real world agricultureal context and two by asking contextualized farmer relevant research questions I seek to better understand how to best design and manage our ecosystems for optimized functioning and
High adoption potential and I seek to take a holistic approach to sustainable propop crop production and therefore I aim to figure out how to harness the critical role that soil microbes and plant soil interactions play in nutrient cycling and crop nutrition in soil Water Dynamics and crop Torance to Drought as
Well as crop resistance to pests the reason for why I would like to look at these three aspects to crop performance is that they are intricately linked and all determined by plant so interactions and I see potential in identifying diversifying practices fostering plants or interactions with synergistic effects on crop nutrition
And resistance to pertubation so to become more concrete about what I seek to further build upon I will share with you some of the research that I conducted in the past this first takes me to a low input AO ecosystem in subsaharan Africa this photo shows the farming system mace fields of subsistence
Farmers in Malawi Farmers that have no study source of income and are relying on their ma heals to feed the family and the trees especially nitren fixing F eria those that you can see in the photo are commonly distributed throughout smaller farmer spes and that’s because they are known
For the positive impact on Soul fertility so with the trees in Farmers fields we have what’s called an AG forestry system and while the positive effect of Agro forestry trees on soil fertility has mostly been attributed to high quality organic met inputs such as tree leaf litter input I was curious to
Find out to what extent microa fungi contribute to the enhancing effect of trees on soil fertility micro fungi or AMF are key root symbion that require plants carbohydrates and in return provide plants with several benefits such as enhanced access to nutrients as well as greater tolerance to aoic and biotic
Stressors and let’s focus on the role of micro fungi in providing host plants with greater access to nutrients so what’s been known for quite some time is the networ of fungal filament fungal Hy they basically increase the surface area of the host plants root systems and as such improve
Access to nutrients so this is shown in the figure on the right you see in the circle on the right the Orange Lines represent pres in the micro Melia networks of fungal filaments that can reach into soil pores that are too small for the root to access and this is in
Contrast to a plan with a root system that doesn’t associate with micro fungi here you can see on the circle on the left the roots only have access to the areas of the soil that the roots can actually get to more recently we gained insight into the potential of micro fungi to connect
Different plants via networks of fungal filaments via Mycelia and transfer nutrients from one plant to another and this could have potential in enhancing sustainability of low input farming systems for instance if nutrients were transferred from well established trees such as mango and F Feria trees that you
Can see in the photo to surrounding crops such as maze however most of our knowledge about micro fungi and interplant nutrion transfer is limited to simplified and small scale po experiments knowledge on whether these findings can be translated to complex systems is still scarce I set up a root exclusion
Experiment around single standing fat trees in farmers’s fields and I used isotope tracing to test the hypothesis that micro fund allow maze to gain access to tree derived nitrogen that is otherwise inaccessible to maze the photo in the bottom shows the experimental setup which allowed us to distinguish the different mechanisms
Underpinning nitron uptake by mace we dug out these plots 1 M by 5 m and half meter deep put in place different types of lining then put the soil back in place let the system rest for a year and then we SE Maze and S maze throughout
The plots to determine the 15n isotopic signature and for the sake of time just briefly the 59 isotopic signature of the nitrogen fixing trees is distinctly different and therefore allows distinguishing the tree derived nitrogen from the so derived nitrogen the figure shows on the x-axis the distance of maze plants from the
Tree so we sampled at one two three four and five meters from the tree on the y- AIS it’s the proportion of tree direct nitrogen in maze leaves and the different colors represent the different mechanisms through which maze obtain the tree derived nitrogen so in green it’s
The um nitrogen that was derived via Leaf litter input in Orange via micro Mycelia that extend beyond the maze rooting Zone and in blue via direct root to root contact between tree and Maze as you can see most of the tree derived nitrogen maze is due to tree
Leaf litter input the green line represents the average of the tree derived nitrogen in maze due to litter inputs what’s remarkable however is that half of that so about onethird of the total tree derived nitrogen in maze leaves is due to micro Melia Roots had basically no effect so these findings further promote
Maintaining trees within fields and additionally they provide some mechanistic insight in that they suggest that managing for micro funi in Farmers Fields can improve crop nutrition which may result in Greater yields but what these findings didn’t tell us was whether the uptake was mediated through a direct tree to ma Neutron transfer or
Tree to soil to mace or in short soil to ma transfer and if it’s the ladder if it’s a soil to ma transfer is is a tree maintained or maze Associated Mia that take up the tree derived Nitro from the soil and transfer it to mace I mentioned Mike Riser fungi
Require plant carbohydrates and so they do present a cost to the to the plant and now the question is do trees or may seedlings cover the cost for these Melia that allow a transfer of Tree Drive nitrogen so I conducted an isoto tracing experiment in the greenhouse I grew
Mango and F IR trees within Malawi and field soil So within the native soil microbiota and then I planted maze two years after I planted the trees into these ingrow cores that prevented a root to- root contact between the Maze and the tree but allowed for potential Nutri transfer via micro
Nwork here’s a schematic of the experimental design so to test a tree toas nutrient F we applied 15n and 33p isotope labeling solution directly to the tree stems via stem injection again just briefly in this case the 59 and 33p that we applied acted like a Dy that we were able to
Trace into ma ceilings to test the soil to ma transfer we applied 15 n and 33p isotopic labeling solution to root free labeling compartments that were burred in the substrate and to to assess the role of tree maintained Melia versus maze Associated Melia we tested the soil toas transfer with and without
Trees before I continue I’d like to direct your attention to the two types of ingrowth cores as mentioned maze was grown in ingrowth cores to prevent Neutron transfer re direct root to root contact between tree and Maze but allow microa Melia to potentially provide maze with access to nutrients from Beyond the inth
Core to control for any non- micro Riser mediated nton transfer we included One ingros Core that was rotated just before label application and that was to break any potential Hy connections between tree and mace so let’s first look at the results for tree to mace nuton transfer the
X-axis shows the sampling Day post label application so we sampled and analyzed ma leaves for 59 and 33p at 74 and 28 days post label application and on the y- axis you see the specific radioactivity of 33p I’m only showing results for 33p but it’s very similar for 15 and
Asar the diamonds and circuits represent maze grown with mango versus FIA and the green shapes represent maze grown in rotated cores so the green shapes show Neutron transfer that was not mediated by micro F because we broke the high fee by rotating the course the blue shapes on the other hand represent
Maze grown in static course and as such show Neutron transfer mediated by microa funi you can see that there’s no difference in the amount of 33p obtained by Maze grown in the rotated course the green and the static course so these results provide no evidence for a tree to ma Neutron transfer mediated
By micro fungi for the soil to maze newon transfer the layout of of the figure is basically the same with the addition of the triangles representing maze grown without trees and here we do see that Maze and static course so the blue shapes show greater 33p than those where micro
Mediate transfer was not possible you see the green shapes are all around zero and it’s only the blue shapes that show an increase in 33p in mace with time however however there was no statistical difference in the amount of nutrients obtained by Maze growing with and without trees so clearly maze
Seedlings effectively establish their own microa Melia that provide them with access to nutrients from outside their rooting Zone and so it’s possible that may seedings simply rely on their own Melia to obtain nutrients even in the presence of already established pre maintained micro Mia to summarize my findings show that
Regardless of whether it is maze Associated or tree maintained micro Melia or a combination of both microor fungi can improve nutrient uptake by crops and as such likely play a role in the positive effect of aqu Forestry trees on SOL fertility crop years okay so now let’s move from the
Low input AGR forestry system in Malawi to an intensive Horticultural production system in California intensively managed agricultur systems such as shown in the photo typically show a lower micro abundance and diversity than natural systems and there are two likely reasons for this one crops are well supplied
With nutrients and two in intensive soil management presents a high level of disturbance breaking micro networks and both of these factors affect the functioning of the symbiosis as soil Health Management has gained increasing attention so have soil microbes and biion inoculants biion Ulin are products containing beneficial microbes known to promote plant
Growth there has been curiosity as to whether or not inoculating crops with microor fungi improves crop performance in these intensively managed agricultur systems they have been result the effect OFA props with micro Reser fungi some studies show a positive others show no effect we tested whether the effectiveness of micro inoculation of
Crop seedlings in improving yields would depend on soil management practices we worked with tomatoes in this case and we found no clear effect of inoculation so this figure shows on the x-axis the 20 different fields that we worked on on the y- axis the difference in marketable yield between inoculated and noninoculated
Plots the data points above the line show a positive response to inoculation and the data points below the line indicate a negative response to inoculation you can see the points are all over the place the different colors represent six different soil management practices so we had different types of
Green waste and manure as well as no organic matter Amendment so we found no difference neither in yield nor in food quality between inoculated and non-inoculated plots and so to me these results drive home the point that we can’t achieve sustainable agriculture by simply relying on external inputs whether it’s bio ulence izer
Pesticides instead we have to figure out how to best design and manage farming systems that support optimal plant so interactions to harness plant so interactions we have to better understand how to best condition the soil in a given system so we we know that a previous crop affects the soil
Differently and the subsequent crop differently than another crop and there are overwriting factors such as landscape structure and soil properties that further impact these plant soil interactions as well as plan PL interactions and this knowledge has already been used to develop suitable crop produ U crop rotations for example
However what fulfills one purpose May defeat another and of course depending on the AG ecosystem we may have to adjust the way that we harness plant so interactions in the simple m based Agro forestry system trees can for for instance help maintain micro networks in the soil during the non propping season
And improve soil structure and therefore nutrient retention in more intensive agricultur systems we may for example promote the abundance of micro rizer fungi through the use of micro rizer cover crops and minimal soil disturbance and this leads me to the work that my current PhD students plan
To work on within the local agricultur system here in Germany the focus will again be on the micro Isis and biosis but beyond determining the role of micro fungi in crop nutrition we will examine crop Torance to water stress and insect deivery why water stress and insect aivy well because clearly both are
Relevant when aiming to achieve sustainable CR production but specifically because micro of fer a known to affect both with regard to water Studies have shown that micro of fungi affect water relations such as stomato regulation in ways that may optimize the responsive responsiveness of plants to low or variable soil
Moisture also micro isop fungi stimulate antioxidant enzyme activity which alleviates damage caused by reactive oxygen species under drought stress and this can then improve water use efficiency and recovery of plants post drought further by enhancing plants access to nutrients micro fungi can maintain the physiological performance of plants and
This has indirect effects on on Water Dynamics as it strengthens plants ability to recover and or prevent severe de severe damage of roots and the photosynthe photosynthetic appar with regard to insect aivy there are again indirect effects of micro fungi enhanced access to nutrients leads to Greater Plant vitality and as such could
Result in Greater resistance of corops to insect aivy the establishment of the micro Riser symbiosis in itself May Prime plant defenses this is referred to as microa induced resistance and what I find particularly intriguing is that there’s evidence for micro rizon networks to transfer warning signals it’s been shown under controlled
Conditions that intact micis Mycelia transfer warning signals from one plant that is attacked by insects to neighboring plants that are not yet attacked by insects and the warning signals cause neighboring receiver plants to boost up their immun system making making them less susceptible to insecty however the caveat remains that
Intensive agriculture systems negatively affect m f and break micro networks in the local agricultural systems cover crops that are typically grown prior to a main crop can present a viable option to manage for micro networks if the cover crop is a species that Associates with micro fungi which
Are basically all but members of the brassic AC and kop AC then the soil will likely be well colonized by microa networks intact microa networks in the soil present the best source of microa propes leading to the fastest recolonization of crops and subsequent benefits to the plant with regard to
Access to nutrients water relations and resistance to CL so from the perspective of the micro in biosis to keep micro networks in the soil undisturbed there may be good reasons to Pro promote notive systems so the first question that we will address this coming season is do intact undisturbed microa
Melia established through cover crops and maintained by performing no till improve the tolerance of the proceeding main crop to water stress and insect deivery compared to tillage Disturbed micro Melia we will start with explorative explorative field experiments and later then combine it with mechanistic experiments to actually decipher the role that micro networks
May play in enhancing crop tance dist stressors okay I will leave it at this more to come as we progress with this work so now just a quick recap with my research I strive to better understand and learn how to manage plans or interactions for greater crop nutrition tolerance to drought and
Resilience to pests and as such take a holistic approach to attain sustainable crop production and Al together with my work I aim to help work towards attaining food and nutrition security as well as reducing the environment footprint of agriculture and with that I’d like to acknowledge the people that were involved in the
Work that I have presented to you today mentors colle students assistance farmers and I’d like to thank you for your attention happy to take any questions