Effect of substrate stratification on growth of common nursery weed species and container-grown ornamental species

Authors: YVRAJ, KHAMARE - University Of Florida; MARBLE, CHRISTOPHER - University Of Florida; Altland, James; PEARSON, BRIAN - University Of Florida; CHEN, JIANJUN - University Of Florida; DEVKOTA, PRATAP - University Of Florida

Submitted to: HortTechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2021
Publication Date: 1/9/2022
Citation: Yvraj, K., Marble, C., Altland, J.E., Pearson, B., Chen, J., Devkota, P. 2022. Effect of substrate stratification on growth of common nursery weed species and container-grown ornamental species. HortTechnology. 32(1):74-83. https://doi.org/10.21273/HORTTECH04965-21.
DOI: https://doi.org/10.21273/HORTTECH04965-21

Interpretive Summary: Weed control is one of the most costly and challenging aspects of pest management in nursery production. Preemergence herbicides are the most common tool used for weed control; however, preemergence herbicides are expensive and cannot be used on sensitive crops or inside enclosed structures. Substrate stratification is the intentional layering of different substrate components or different substrate particle sizes within the vertical profile of the container where each layer performs a specific function. The use of coarse substrates on the container surface has been shown to be an effective weed management tool. The objective of this research was to evaluate the effects of a substrate stratification technique that used more coarse particle pine bark as the top layer and more fine textured bark incorporated with fertilizer as the bottom layer on the growth of common nursery weeds and container ornamental plants. Substrate stratification with more coarse bark on the top decreased the growth of two of the most common nursery weeds bittercress (Cardamine flexuosa) and liverwort (Marchantia polymorpha) by 80% to 99%. Substrate stratification initially reduced the growth of ligustrum (Ligustrum japonicum) and blue plumbago (Plumbago auriculata), but growth was similar to non-stratified industry standard substrates by the end of the experiment at 24 weeks. This research demonstrates that substrate stratification could be used as an effective weed management strategy for container nursery production.

Technical Abstract: Substrate stratification is a method of filling nursery containers with “layers” of different substrates, or different textures of the same substrate. Recently, it has been proposed as a means to improve drainage, substrate moisture dynamics, and optimize nutrient use efficiency. Substrates layered with larger particle bark as the top portion and smaller particle bark as the bottom portion of the container profile would theoretically result in a substrate that dries quickly on the surface, thereby reducing weed germination, but that would also retain adequate moisture for crop growth. The objective of this study was to evaluate the effect of stratified substrates on the growth of common nursery weeds and ornamental crops. This study evaluated the use of coarser bark (<0.5 or 0.75 inches) as the top substrate and finer bark (<0.38 inches) as the bottom substrate with the goal of reducing the water-holding capacity in the top 2 to 3 inches of the substrate to reduce weed germination and growth. Results showed that substrate stratification with more coarse bark on the top decreased the growth of bittercress (Cardamine flexuosa) by 80% to 97%, whereas liverwort (Marchantia polymorpha) coverage was reduced by 95% to 99%. Substrate stratification initially reduced the growth of ligustrum (Ligustrum japonicum) and blue plumbago (Plumbago auriculata), but there was no difference in the shoot or root dry weights of either species in comparison with those of nonstratified industry standard substrates at the end of 24 weeks. The data suggest substrate stratification could be used as an effective weed management strategy for container nursery production.