Ferguson et al. showed that a 3.7 cm layer of wood chip mulches from southern redcedar E. Murray and southern magnolia provided control of redroot pigweed and large crabgrass Scop.Mulch products would likely be applied at or near the time of potting, and presumably would be applied to containers free of weed seed. Any weed seed introduced into the container thereafter would have to germinate and establish on the surface of the mulch product. Alternatively, mulches could be applied sometime throughout the production cycle of a crop. Containers might be hand-weeded to remove existing weeds, and then mulched. In this scenario, a large weed seed bank could be present on the substrate surface. Seed present at the time of mulch application could germinate from beneath the mulch product. A third scenario would be the carryover of weed seeds from liners into larger containers at the time of transplant. In this situation too,indoor cannabis grow system a seed bank present on or near the surface of the newly potted liner would have to germinate and establish through the mulch. Establishment of weed seed above and below mulch products has been studied previously. Cochran et al. showed that placement of eclipta or prostrate spurge seed above or below 1.3 to 2.5 cm pine bark mulch had no effect on weed number or fresh weight accumulation.
Likewise, Richardson et al. showed that bitter cress and oxalis establishment in containers mulched with 3.8 to 7.6 cm pine bark was not affected by seed placement above or below the mulch. Parboiled rice hulls are dry rice husks removed from rice grains with steam or hot water. Hereafter they will be referred to as rice hulls. Rice hulls are commercially available for horticultural use, and are currently used as a component in greenhouse and nursery substrates. Rice hulls can also be used as a container mulch. One manufacturer recommends a rice hull mulch depth of 3.8 to 5.0 cm for effective weed control in container crops. Previous research has shown that rice hull mulch at a depth of 2.5 cm provides excellent flexuous bitter cress and liverwort control when seed or propagules are disseminated onto the mulch surface . The objective of this research was to determine if application of seed above or below the mulch surface affects flexuous bitter cress or creeping wood sorrel establishment. Repeated measures analyses showed that flexuous bitter cress numbers and shoot fresh weight when seeded above the mulch layer were affected by the interaction of time and rice hull depth Containers with 0.6 cm rice hulls had fewer established flexuous bitter cress than non-mulched controls with the exception of 4 WAP. Despite reduced numbers, shoot fresh weights of bitter cress with 0.6 cm rice hulls were similar to non-mulched controls with the exception of 8 WAP.
Containers with 1.3 or 2.5 cm rice hulls had similar flexuous bitter cress numbers and shoot fresh weight,cannabis grow set up and both were significantly lower than non-mulched controls or those with 0.6 cm rice hulls. No flexuous bitter cress established throughout the experiment when seeded above 2.5 cm rice hulls, similar to results observed by Altland and Krause . Weed numbers among containers with flexuous bitter cress placed beneath the mulch changed over time . Flexuous bitter cress numbers declined sharply from 4 to 8 WAP, as many of the applied 40 seed had germinated by the first harvest date.There were no differences in bitter cress number or shoot fresh weight with respect to rice hull depth from 8 to 16 WAP. Lack of differences among mulch treatments was due to there being relatively few bitter cress germinating after the first harvest. There was an interaction between seed placement and rice hull depth on percent establishment . Non-mulched controls in both groups had similar percent establishment . Establishment decreased linearly and quadratically when seed were placed above the mulch, with lower establishment in 0.6 cm rice hulls compared to non-mulched controls. In contrast, establishment decreased linearly when seed were placed beneath the mulch layer with only the greatest rice hull depth reducing establishment below the non-mulched controls. At each rice hull depth , establishment was lower when seed were placed above the mulch layer than when placed below the mulch layer. At 4 WAP, creeping wood sorrel number and shoot fresh weight were affected by an interaction between seed placement and rice hull depth .