Effects of compost fertility on the growth, yield, and nutrient content of lettuce (Lactuca sativa)

Authors: FLOOM, MELODIE - THE OHIO STATE UNIVERSITY; Altland, James; MICHEL, FREDERICK - THE OHIO STATE UNIVERSITY; SAMARAKOON, UTTARA - THE OHIO STATE UNIVERSITY; LING, PETER - THE OHIO STATE UNIVERSITY

Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/29/2024
Publication Date: 3/29/2024
Citation: Floom, M., Altland, J.E., Michel, F., Samarakoon, U., Ling, P. 2024. Effects of compost fertility on the growth, yield, and nutrient content of lettuce (Lactuca sativa). Acta Horticulturae. 1389:139-152. https://doi.org/10.17660/ActaHortic.2024.1389.17.
DOI: https://doi.org/10.17660/ActaHortic.2024.1389.17

Interpretive Summary: Compost is one of the most frequently used fertility sources in organic production. Its physical properties are often comparable to peat and it can contain high levels of plant-essential nutrients. Compost is a sustainable resource that reduces the need for unsustainable growing media as well as expensive and high-energy cost N-P-K fertilizers. The objective of this study was to determine if compost used at 30% (by volume) of a growing media could be used as the sole fertility source for container-grown lettuce (Lactuca sativa). The composts included one generated from a modified static aerobic pile, yard trimmings, dairy manure, food scraps, and a home compost. Additional control treatments included non-compost amended growing media fertigated with either a conventional fertilizer or an organic fulvic acid. Compared to the two control treatments, compost as a one-time organic fertility source was capable of sustaining lettuce growth for a short period but was unable to provide the necessary essential nutrients for lettuce to reach maturity or a marketable size. Multiple applications of compost or supplementation with a secondary organic or conventional fertilizer may be necessary for a complete production cycle of lettuce.

Technical Abstract: In the last decade, the consumer demand for organic produce has increased 500% causing a surge in the development of organic farms. The constraints of organic farming limits the number of fertility and pesticidal sources that are allowed in agriculture to sources derived by plant and animal products or directly mined. Compost is a renewable organic resource that is capable of providing fertility and microbiome diversity to soil and soilless culture thereby reducing the need for inorganic fertility and pesticidal sources. In this study, the efficacy of a one-time application of several different composts to lettuce were evaluated after six weeks based on lettuce yield and nutrient content. Composts varieties including: food scrap, home, dairy manure, yard trimmings, and microbially inoculated were mixed at 30% (volume based) with an 85:15 peat perlite blend. Composts in general appeared to have decreased in nutrients at approximately 4 weeks after potting. Dairy manure compost produced among the highest yields for the compost treated lettuce and did not exhibit deficiency related disease. However, all compost treated lettuce had lower yields and foliar nutrient concentrations than the controls. While compost does provide fertility, it may not be enough to sustain the nutrient demand of crops. Therefore, multiple applications of compost or supplementation with a different fertility source is recommended.