Sulemana Issifu

University of Hohenheim, Institute of Agricultural Sciences in the Tropics (Hans- Ruthenberg Institute), Stuttgart, Germany

Supervisor: PD Dr. Frank Rasche

Background

Agriculture, since its advent some 12,000 years ago, has had a negative impact on nature through intensification. It includes leaching of nitrogen (N) and trace gas emissions accelerating climate change (CC). Likewise, drought, a major threat from CC, has put crop production in jeopardy. A proposal that is amplified as panacea for achieving an agricultural system that harmonises nature with productivity, is the perennial grain cropping system (PGCS). Using natural ecosystems, such as grasslands as reference, PGCS is touted for ecological and CC mitigation/adaptation potentials. In dealing with the N problem, biological nitrification inhibition (BNI), a nature-based solution, is mentioned as antidote to compromise N losses from agricultural systems. Whether or not PGCS can provide this ecosystem service (BNI) as observed in annuals like wheat, rice, etc, is the main knowledge gap that constitute the foundation of this study.

Objectives and Research Questions

The main objective of the research is to investigate the potential of PGCS to achieve BNI under climate-induced water stress as modulated by crop-associated microbiome. AGCS are regarded as control systems. Accordingly, the following research questions build the overall frame of the study: 1. Do PGCS have the capability to maintain a mutual relationship with the crop-associated microbiome (AMF, nitrifiers compromised by BNI) under abiotic stress, allowing the consistent release of BNI inducing metabolites/exudates in the rhizosphere? 2. How are the functional traits of the targeted microorganisms related to microbial N cycling affected by PGCS? These questions are answered by testing the hypothesis that, under drought conditions, PGCS with its associated microbiome (AMF, nitrifiers) achieve a higher BNI potential than AGCS. The hypothesis is founded on the assumption that PGC are efficient resource users (K strategy) relative to AGC (r strategy) and so, PGC reveal a higher resilience potential to abiotic stressors (e.g. drought) than AGCS.

Methods

1. Experimental baseline

An ecology approach undergirds this study. As a general approach to this research, in situ field trials in addition to in vitro laboratory testing will be conducted. Field trials involve established PGC and AGC systems (Sweden, Belgium, France) allowing the integration of different water and agro-ecological conditions. Planned in vitro experiments will be set-up at University of Hohenheim.

2. Microbiome studies

Using the in situ experiments, metagenomics will be performed to characterise the microbiome and its functional traits. High-throughput sequencing (Illumina Myseq amplicon sequencing) will allow identification of the taxonomic complexities in PGCS and compared with that of AGCS.

3. Metabolome studies

Using the in vitro experiments, root metabolites will be collected and tested for their effectiveness in achieving BNI. A metabolomic approach will be used for the chemical characterisation of metabolites using gas and liquid chromatography-mass spectrometry (GC-LC-MS). Analysing BNI effects between the two cropping systems will be accomplished by developing highly sensitive bioassays that can detect and quantify nitrification inhibitors produced by plants, and the associated microbiome.

4. Analysis and integration of data

Integrative data analysis using statistical software (mainly R statistic) will be performed to consolidate data obtained during the experimental phase. It includes publishing of peer-reviewed journal articles.

Expected Results

Project outcomes will contribute to knowledge on sustainable farming practices such as water/nutrient conservation, CC mitigation/adaptation, and biodiversity protection in conjunction with EU Commission’s (EC) proclamation on these issues. The EC may use the outcomes to make a case for PGCS as this will align with its overarching objective to leverage nature-based solutions to guarantee sustainable agricultural productivity. Another expectation, as related to the research hypothesis, is to engender the interest of farmers to adopt PGCS because of their benefits. Aside the increase in biomass for foraging and grains, water competitiveness and nutrient provision known as features of PGCS, this project will help to unravel the BNI potentials of PGCS in relation to the crop-beneficial functional traits of the microbiome. Prospectively, this could save farmers the cost of buying excessive fertilizers and allow them to fulfil the regulatory obligations on N use. Here, farmers could explore the results to curtail economic losses they incur due to N leaching/losses valued at US$15 billion annually in the US. Also, 57% of surveyed farmers in the US and France have showed preparedness to adopt PGCS, and it is expected that, the results will serve as impetus for such farmers to hurriedly accept PGCS.