Green manure: An ancestral, sustainable and economic agricultural practice for the dryland agricultural systems of the Mediterranean Basin

The European LIFE AMDRYC4 project develops adaptation actions based on natural ecosystems associated with dryland farms in areas affected by climate change. The project implements practices with green manure which is ideal for dryland agricultural systems and has a long tradition in the Mediterranean Basin. Nevertheless, green manure has been overshadowed during part of the last century by other practices that were often less sustainable.


But what is green manure? Green manure, also called cover crops, consists of planting certain crop species, such as leguminous, gramineous, cruciferous plants. Combined in rotation, succession or association with other commercial species, these plants contribute to recover, and improve biological, physical and nutritional properties of the soil. Green manure increases soil organic carbon and nutrient content, especially nitrogen if using leguminous species that promote nitrogen fixation,  it increases biodiversity rates, improves soil structure, water infiltration, and reduces evapotranspiration, soil erosion, nutrient leaching, outbreaks, and weed coverage. In general, green manure is economic, environmentally friendly and easy to implement by farmers.

Green manure has been planted in the AMDRYC4 experimental plots located in Corvera (Murcia, Spain) and Nogalte (Lorca – Velez Rubio, Spain). The goal is to objectively quantify the ecosystem and ecological benefits that this practice has over agricultural dryland farms, in general, and over the physical and chemical soil properties, in particular. Corvera experimental plot includes almond, olive, and carob rainfed trees, while Nogalte experimental plot is an almond farm. Vici sp. and Hordeum sp. (barley) species have been planted in Nogalte as green manure, and Avena sp. (oats) in Corvera. According to traditional methods, seeds were distributed over the fields and between the tree lines in fall, i.e., during the rainy season; and the green manure has been harvested and incorporated into the soil in June, before fructification, to reduce the loss of nutrients in the green parts of the plants due to the seed production. During the plantation season, the land cover has protected the soil, reducing erosion and suppressing weeds. Soil organic carbon and nutrient content were measured before seeds were planted and will be measured again next year. Expected results will likely show an increase in soil organic and nutrient content, and improvements in soil structure properties.

The experiments with green manure done in Covera and Nogalte, will be the baseline to assess the ecological, economic and ecosystem benefits that a generalized use of green manure would have in the agricultural dryland systems of the Mediterranean Basin.

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