A Biobased Mulch Innovation for Organic Spinach and Carrots
Project Director
Samuel Wortman
Year Funded
2020
Award Number
2020-51106-32380
Funded Institution
Universityof Nebraska
Grant Program
ORG (Organic Transitions)
USDA NIFA Report
Project Overview
Organic production of direct seeded crops like carrots, lettuce, and spinach often entails manual weeding. In this study, seeds were planted atop polylactic acid (PLA) biodegradable film mulch and covered with ¼ to ½ inch of compost. Crop roots penetrated the mulch to enter the soil while light exclusion and physical hindrance suppressed weeds germinating beneath the mulch. Three years of field trials compared crop establishment and yield, weed emergence, soluble nitrogen (N), and foodborne pathogens in crops grown with PLA mulches formulated with or without organic fertilizer and covered with two different composts, versus no-mulch controls.
Farmer Takeaways
(1) Small-seeded crops like carrot and lettuce sown on top of a polylactic acid (PLA) based biodegradable film mulch and covered with ½ inch of compost can penetrate the mulch, while weed seeds under the mulch are suppressed.
(2) Reduced labor costs for weeding give good return on investment in mulch and compost.
(3) Laying mulch over pre-formed seed furrows can prevent loss of compost and seeds to runoff during heavy rains.
(4) PLA mulch and plant-based compost do not pose foodborne illness risk, while manure-based compost may somewhat increase risk.
(5) This technology remains experimental as of 2026, as no NOP-approved biodegradable film mulches are commercially available.
Project Outputs
Wehrbein, C., I. Kadoma, and S.E. Wortman. 2024. First field evaluation of a polylactic acid-based weed barrier with compost for carrot production. HortTechnology 34(2):204-210.
Shcherbatyuk, N., S.E. Wortman, D. McFadden, S. Weyers, W. Ahmad, D. Bajwa, S.P. Galinato, A. Formiga, G. Gramig, and L.W. DeVetter. 2024. Alternative and emerging mulch technologies for organic and sustainable agriculture in the United States: A review. HortScience 59(10):1524-1533.