A recent study (Leoni et al., 2024) conducted by the Scuola Superiore Sant’Anna and the Research Institute of Organic Agriculture (FiBL) explored the use of legumes as living mulches in a crop sequence of durum wheat and forage sorghum.
The eight selected legume species do not influence nitrogen uptake by wheat but can provide up to 182 kg of nitrogen per hectare, supporting sorghum production without additional fertilisers.
Lupine grass (Hedysarum coronarium) and white clover (Trifolium repens) stood out for their agro-economic performance. (1)
1) Agroecology, introduction
Agroecology is indicated by FAO as the main way to reconcile the economic sustainability and sustenance of agricultural businesses with the objectives of protecting the environment and the health of populations. (2,3,4)
The integration of legumes with durum wheat, as analyzed in the current study (Leoni et al., 2024), represents an exemplary agroecological practice.
In fact, legumes, through nitrogen fixation, enrich the soil, reducing the need for synthetic fertilizers and improving the yield of durum wheat.
1.1) Mulching
Living Mulches (LMs) and cover crops represent utility, green manure, companion crops, often legumes, that are grown alongside the main crop and maintain ground cover throughout the entire growing season.
In this way, they effectively replace chemical weed control and contribute to the optimization of the nutrient cycle without damaging crop yields.
1.2) The relay association
The two main modes of cultivation of living mulches are contemporary intercropping and relay intercropping. The latter is highlighted as particularly advantageous since it confers a competitive benefit to the main crop and can be adopted if environmental conditions do not allow the establishment of cover crops at the time of sowing the main crop.
The persistence of legumes after harvesting the main crop allows the soil to be constantly covered until the next crop, with positive effects on weed control, the microbiome, the reduction of soil erosion and support for the productivity of subsequent crops.
2) Legumes and durum wheat, the study
The current study was conducted at the ‘Enrico Avanzi’ Agri-Environmental Research Center of the University of Pisa, Italy, in two agricultural fields with soils of different composition. A biennial crop sequence was carried out with durum wheat (Triticum durum Desf.) and intercropped legumes, followed by a spring crop of fodder sorghum (Sorghum bicolor (L.) Moench).
The researchers examined the effects of eight different species of living mulches (perennial and annual) intercrops and cover crops on
- nitrogen dynamics. Total nitrogen was measured in wheat straw and estimated in grains. Nitrogen use efficiency (NUE) was calculated to evaluate how much nitrogen was
- absorbed compared to how much was supplied,
- weed control,
- protein content of the wheat, analyzed after threshing to obtain clean grains,
- biomass production of crops, harvested at the maturity stage,
- crop production,
- analysis of gross income (gross production value and variable costs) to evaluate the economic sustainability of the mixed crop.
3) Results
From the results of the study it emerges that the weather conditions have a significant impact on the behavior of legumes:
– annual legumes such as T. incarnatum and T. resupinatum had a limited impact on wheat biomass production in a year with low rainfall. During the year with better weather conditions, they contributed significantly to the nitrogen supply,
– self-pollinating legumes, such as T. subterraneum, were found to be more resistant to adverse conditions. While, Hedysarum coronarium and Trifolium repens stood out for their agro-economic performance.
The protein content of wheat was not influenced by intercropping with legumes. According to the researchers, the cumulative effects of legumes could emerge in the long term.
The economic analysis of intercropping shows that cover cropping and intercropping – although involving additional costs, such as the purchase of legume seeds – can maximize gross income on a crop sequence when choosing the right legumes. This can reduce the need for external inputs such as fertilizers and herbicides.
4) Conclusions
The adoption of agroecological practices – such as cover cropping, Living Mulch and intercropping – requires careful selection of legume species suitable for local conditions to maximize the benefits of intercropping, the researchers conclude.
Further research is needed to evaluate the cumulative effects of legumes during crop rotations.
Dario Dongo and Gabriele Sapienza
Cover image by Mathias Cougnon, Jean-Louis Durand, Bernadette Julier, Philippe Barre, Isabelle Litrico. Using perennial plant varieties for use as living mulch for winter cereals. A review. Agronomy for Sustainable Development (2022) 42:110. https://doi.org/10.1007/s13593-022-00844-x
Footnotes
(1) Federico Leoni, Mariateresa Lazzaro, Stefano Carlesi, Anna-Camilla Moonen. Screening suitable legumes for living mulches to support nitrogen dynamics and weed control in a durum wheat-forage sorghum crop sequence. Field Crops Research, Volume 307, 2024, 109246, ISSN 0378-4290, https://doi.org/10.1016/j.fcr.2023.109246
(2) Dario Dongo, Camilla Fincardi. Agroecology, SDGs, salvation. The FAO Decalogue . GIFT ( Great Italian Food Trade ).
(3) Dario Dongo, Alessandra Mei. Big philanthropists are looking at agroecology . GIFT ( Great Italian Food Trade ).
(4) Marta Strinati. Agroecology, 6 systems compared. The advantages of organic for farmers . Analyses. GIFT ( Great Italian Food Trade ).
Dario Dongo, lawyer and journalist, PhD in international food law, founder of WIISE (FARE - GIFT - Food Times) and Égalité.
Graduated in Agronomy, with experience in sustainable agriculture and permaculture, laboratory and ecological monitoring.
