26.09.2024
In a recent study, an international research team involving the Leibniz Center for Agricultural Landscape Research (ZALF) has investigated the performance of co-designed diverse crop rotations in comparison to continuous cereal cropping in the mediterranean region. The results of the published study in the European Journal of Agronomy show single legume integration improved agronomic and economic performance while rapeseed or multiple legume integrations had diverging impacts. Among the first studies in the region to combine participatory approaches and modelling methods, this study emphasizes the importance of involving a diverse panel of stakeholders in the design and assessment of cropping systems as well as modelling approaches to inform about practical options available to farmers in their quest for sustainable and resilient farming.
The research team, consisting of scientists from Spain, France and Germany, focused on the Ebro Valley in Spain, a region with challenging pedoclimatic conditions. In order to develop practical solutions, the researchers worked closely with farmers and other relevant local stakeholders.
In a first workshop, existing cropping systems and their challenges were identified, and diversification options were co-designed in a participatory approach with local stakeholders. In a second workshop, stakeholders assessed the diversified systems based on the modelling results. The new diversified systems were cereal based rotations that included legumes and/ or rapeseeds every 2 or 4 years with reduced tillage and partially replacing synthetic N fertilization with locally sourced swine manure. Using the one-dimensional daily step soil- crop model STICS, the agronomic and environmental performance of the new designed cropping systems were simulated for every day over a period of 21 years in order to assess their long-term effect and their response to increasing climate variability. An economic performance was conducted as well.
Diversification: the trade-offs between agri-environmental and socio-economic impacts
Nitrogen surpluses from manure are abundant in the Ebro valley in Spain and require appropriate management to minimize environmental risks (e.g. contamination of groundwater). The substitution of mineral Nitrogen with manure in the diversified systems and integration of legumes that are capable of biologically fixating Nitrogen has led to an increase in available mineralized Nitrogen.
"Peas have the ability to fixate nitrogen from the air in their roots and thus increase its pool available to the following crops," explain
Ferdaous Rezgui and Genís Simon-Miquel, co-authors of the study and scientists in the "Resource-Efficient Cultivation Systems" Working Group at ZALF. In return, rapeseed can root through deeper layers of soil and absorb the nitrogen available there, which is not accessible to other crops. A great example of niche complementarity through crop diversification.
However, crop diversification also brought with it unexpected environmental problems. For example, the researchers observed increased nitrogen losses in the diversified systems as a result of ammonia volatilization and nitrate leaching since soil available Nitrogen was abundant.
Wheat and barley grain yields remained stable with diversification. Pea and rapeseed yields were higher when they were integrated separately in the rotation rather than combined. Energy yields dropped by 20 percent when peas and rapeseed were introduced in the same rotation, and by 10 percent when introduced separately.
From an economic perspective, the diversified systems showed mixed results. While the system, wheat-pea-wheat-barley, was able to increase gross profit by 12 %, profits in other systems fell or remained unchanged. However, manure use in diversified systems has resulted in significant savings on fertilization costs by reducing mineral Nitrogen use. For the system with pea, savings of 68 % compared to the reference system (continuous cereal cropping) were achieved.
The results of this study can be used as a basis for refining and designing more appropriate diversified options in the region.
Project partners:
- Universitat de Lleida, Agrotecnio-CERCA Center (Spain)
- Innovation, Université Montpellier, CIRAD, INRAE, Institut Agro (France)
- Leibniz Center for Agricultural Landscape Research (ZALF) (Germany)
Funding information:
This work was funded by the Spanish Agency for Research (grant PCI2020-112297, funded by MCIN/AEI/10.13039/501100011033 and the European Union Next Generation EU/PRTR) under the PRIMA Foundation, Call 2019-Section 2-BIODIVERSIFY, a program of the European Union. The project received further support from the SusCrop-ERANET LegumeGap project, PCI2019-103597, funded by MCIN/AEI/10.13039/5011 00011033, co-funded by the European Union and by the ECO-TRACE research project, TED2021-131895A-I00, funded by MCIN/AEI/10.13039/5 01100011033 and the European Union NextGenerationEU/PRTR. Daniel Plaza-Bonilla is Ramon y Cajal Fellow (RYC-2018-024536-I), co-funded by MICIN /AEI/10.13039/501100011033 and the European Social Fund. Louise Blanc was funded by a university contract from the University of Lleida. Laure Hossard was funded by the ANR (grant number: ANR-19-P026-0008-01). Ferdaous Rezgui was funded by the Federal Ministry of Education and Research (BMBF), Germany (grant number 01DH20014), under the PRIMA Foundation, Section 2 Call 2019 - Multi-topic.
