Valorization of organic residues for lettuce production minimizes nitrogen loss in soil in comparison to mineral fertilization

Abstract

The agri-food industry, produces organic residues that could be reused as fertilizer, thereby allowing the recycling of nutrients for crops and the replacement of mineral fertilizers. In this context, here we examined the capacity of anaerobic digestates and mixed residues (digestates plus spent mushroom substrates) to supply nutrients to lettuce (Lactuca sativa L.) grown in a greenhouse experiment. Moreover, the potential leaching of nutrients into the soil was evaluated in a column assay. The results obtained from organic residues treatments were then compared to those achieved in soil treated with mineral fertilizer and in untreated soil. Digestates treatments minimized the potential risk of nitrate (NO₃⁻) leaching by allowing the slow release of NO₃⁻ maintaining crop yield. Given our observations, this type of organic residues emerges as an alternative to mineral fertilizer. The loss of NO₃⁻-N from the total amount of N applied reached ∼3% in the mixed residues treatments, 36–46% in the digestate treatments, and 68% in the mineral fertilizer treatment. The mixed treatments showed low available N content as a result of immobilization in the soil, which is a limiting factor for crop production. Moreover, the organic residues treatments had no negative effect on lettuce seed germination or plant growth with respect to parameters such as chlorophyll, total polyphenols, and heavy metals in aerial biomass. The findings reported herein contribute to a better understanding of nutrient availability provided by organic residues materials and the capacity of these amendments to replace mineral fertilizers and avoid nutrient loss by leaching.

HIGHLIGHTS

• Digestate treatments showed a similar capacity to maintain lettuce production as mineral fertilizer.

• Mixed treatments did not provide mineral N for the crop by N immobilization in soil.

• Nitrate loss when organic residues were applied was lower than for the mineral fertilizer treatment.

• Soil amendment with organic residues has no negative effects on lettuce yield.

• Digestates emerge as an alternative to mineral fertilizers for lettuce production, reducing soil nutrient loss.

Keywords:

• Anaerobic digestates
• column leaching
• heavy metals
• mixed residues
• nutrient losses
• soil nutrients

Acknowledgement

We thank the staff of the Agro-environmental laboratory of IMIDRA for their support.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the European Union through the European Regional Development Fund and the Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA) [grant number RTA-2015-00060-C04-04] and IMIDRA [grant number FP21-NMO]. M.R. Yagüe was supported by the Spanish Ministry of Science and Innovation (MICINN), INIA, the European Social Fund, and IMIDRA [grant number DOC 2015-021].