B6 - Catch crops

Removal of nitrates from the soil by catch crops

 The catch crops are crops whose main objective is to reduce or minimize losses by leaching of nitrogen remaining in the soil after the main crop. The planting of catch crop absorbs a part of soil inorganic nitrogen to develop, and protects the soil from erosion phenomena and from surface encrustment. It also improves the habitat of the soil microfauna and sometimes increases the landscape diversity of the territory.

 This is a crop that has no productive purpose, so it must be reaped before it reaches flowering. The main profit of the crop is in the form of green fertilizer, once it has been incorporated into the soil and released nutrients to the main crop that will be planted then. However, an object of this project is to study its use as a co-substrate of biogas plants to increase its production.

This action is divided into a first stage of testing (first campaign) and a second stage of real implementation.

a) Stage of testing

In the experimental farming of Mas Badia Foundation, some plots will be planted with several catch crops (oats, ryegrass and rapeseed) that a priori might be interesting agronomically and energetically. The experiment will last for two years in order to determine correctly the crops productivity and the N extraction, and optimize its agronomic management and mechanisation.

At the same time, IRTA Torre Marimon Center’s laboratory in Caldes de Montbui will make the trials on biogas production using as a co-substrate the studied catch crops.

b) Stage of real proving

Once finished the first experimental action and chosen the most interesting crop, a demonstration plot (25-40 ha) with the chosen crop will be used with the aim of having enough amount of substrate to introduce in the co-digestion industrial plant.

 Progress / Results

• Estimating the effectiveness of the catch crops use to minimize the N losses in the fertilization of maize based on: digested liquid manure, undigested liquid manure and mineral fertilizer.
• Comparing the effectiveness of minimizing nitrogen losses among the three tested catch crops: ryegrass, oats and rapeseed.
• Checking these crops impact on the accumulation of phosphorus, copper and zinc in the soil when it is fertilized with organic fertilizers.
• Determining the potential of nitrogen catch crops methanation according to their phenological state and preservation method (silo storage).
• Define the process variables that optimize the livestock manure anaerobic co-digestion with nitrogen catch crops (laboratory pilot plant and industrial plant).
• Getting the data to perform a life cycle analysis of the proposed strategy and to estimate its environmental impact.

Progress / Results