The benefits of organic amendments in fruit orchards

The improved management of soil organic matter is considered the stepping stone for carbon farming.

Agronomic practices adopted in conventional and intensive farming systems, especially in the last decades, contributed to Soil Organic Matter (SOM) mineralization processes, leading to a consequent increase of greenhouse gasses released from agricultural soils, and overall reduced soil health. Because the main aim of farming is to maintain the capacity of soils to sustain steady quali-quantitative yield productions over the years, for the present and future generations, this trend should be reversed. In fact, better soil management should promote a balance between SOM mineralization and humification processes, restoring what is being used and ensuring a constant, if not an increased, soil carbon stock. This is the basic principle of regenerative agriculture.

In fruit orchards of semi-arid Mediterranean regions, improper farming practices are the main cause of depleting soil organic carbon pools, resulting in soil degradation and erosion. However, it has been shown that the addition of organic amendments can have a strong soil healing effect (Badagliacca et al., 2021). Among the several options for soil organic amendments, compost, manure, and digestate produced from plant or animal wastes are considered the most useful, effective and affordable for farmers. These are also the forms of SOM that best fit the circular economy model. In fact, these are most commonly sourced locally and often generated by recycling on-farm crop residues or animal manure.

The application of organic amendments improves a number of soil characteristics, including nutrient availability for plants, the diversity and activity of the hosted microbial communities, as well as its capacity to retain water like a sponge while acting as a carbon sink. These co-benefits are very important, as they can be perceived by farmers in a relatively short period of time, providing an incentive for shifting practices. However, multiple periodic applications over at least a two-years period should be undertaken to achieve long-term soil health regeneration and climate change mitigation.

One of the objectives of Farms4Climate is to assess the impact of organic amendments in a variety of soils for carbon farming purposes. In particular, almond orchards in Spain, fig plantations in Tunisia, and kiwi orchards in Italy will be studied. Results from two consecutive growing seasons will be compared and guidelines for practice implementation will be shared. The consortium's ambition is to provide technical advice on how to manage amendment applications so that they can maximise carbon storage in soil.