. Journal 1 Findings:
According to Ozores-Hampton et al (2002), greenhouse pot trials conducted using immature and mature Municipal Solid Waste-biosolids (MSW) composts as a mulch decreased the percentage emergence and increased MDE (Mean Days to Emergence) of the seeds of several weed species. The greater the depth of composts, the more pronounced were the beneficial effects. Also, it was found that the immature composts, having higher percentages of acetic acid, required less depth of mulch to have the same effect. However, it was noted that the immature compost use would be most suitable where: a) the vegetable crop and the compost mulch were spaced apart to minimize phytotoxic contamination, and b) in locations where odors emanating from the immature compost would not be problematic. As a secondary benefit, the researchers found that a subsequent crop showed the typical beneficial effects of adding the now mature compost to the growing medium.
2. Journal 2 Findings:
Garcia-Martin et al (2007) undertook a field study in Badajoz, Spain, to determine the effects of various fertilizer treatments and weed control measures on a durum wheat crop. For this paper, the weed controls used are the focus of our interest. The measures compared in their field study were; a) no control; b) using a herbicide; c) harrowing using flexible spring tines; and d) inter-row hoeing. Their findings were that the herbicide approach was the most effective, reducing the weed amount by circa 80% relative to the “no control” figure, whilst mechanical weed control by harrowing and hoeing gave weed growth reductions of 40% and 52% respectively. Inter-row hoeing to control weeds also caused a reduced crop yield.
3. Journal 3 Findings:
Chalkos et al (2010) conducted an experiment in which composts made with the additions of aromatic plant materials were used in growing tomato seeds in pots, under controlled conditions. The aromatic plants used to make the composts were Spearmint (Mentha spicata) and Sage (Salvia fruticosa). The purposes of the experiment were to: a) measure the growth of soil bacteria and fungi; b) the number of weeds developing; and c) the above and below ground growth of the tomato plants. For our purposes, the weed growth figures are of interest. It was found that using compost with between 4 and 8% of added Spearmint, weed growth was reduced – especially of broadleaf weed types, at the same time as stimulating growth of the tomato seedlings. The researchers concluded that the essential oil in Mentha spicata was the agent that caused suppression of weed germination and growth. The same effects were not seen from the compost treated with the Salvia fruticosa.
4. Journal 4 Findings:
In 1999, Ozores-Hampton et al evaluated the effects on weed seed germination of differing degrees of maturity of MSW and biosolids. Compost ages used for the evaluations were: three days, four weeks, eight weeks, and one year (mature). All but the mature compost inhibited weed germination and growth and caused a decrease of the germination index (germination percentage and growth combined). The only exception to this general finding was in the case of Cyperus esculentus (the yellow nutsedge), which was not affected in the same way. In general though, the evaluation exercise indicated that using immature MSW-biosolids in between crop rows could be a useful weed control method.
5. Journal 5 Findings:
According to Ozores-Hampton et al (2001), the composting industry have to consider the maturity of compost products if they are to offer top quality products to the market. In this paper they evaluated the potential use of immature MSW and biosolids composts as a mulch for weed control in between crop rows. Comparisons were made in two trials at Immokalee, Florida – the first conducted in the fall of 1995 and the second the following spring. In all cases the treatments were applied in between the rows of bell pepper and zucchini squash crops which were covered with polyethylene. Two “ages” of compost were used: 4-weeks old and 8-weeks old. The mulch was applied at two depths in each case and compared with a paraquat treated area and another area with no weed control measure at all. The outcome of the trials was that the mulch of immature composts successfully inhibited weed growth in all cases, and that increased depth of the mulch and the “youth” of the 4-week old compost gave better results – up to 240 days of weed germination inhibition. All these results were better than the herbicide (paraquat) treated areas and those with no treatment, suggested that the use of immature composts as a weed suppressing mulch in between row crops could be a successful measure. A concern was expressed about the residual man-made materials (glass, plastics, etc) in the composts, which could be hazardous to agricultural workers later on.
6. Journal 6 Findings:
Krogmann et al (2008) investigated the effects of using an unusual mulch – cranberry fruits and leaves – on blueberry plants. The purposes of the study were to determine the effects on: a) nutrient uptake; b) fruit yield; c) soil chemical properties, and d) weed suppression. Our focus is primarily on the weed suppression results. The study was over a two-year period, taking advantage of an over-production of cranberries at the time. The mulches of either cranberry fruits or leaves appeared to result in lower blueberry fruit yields in the second year of the trial, suggesting that these mulches were not successful in regard to crop productivity, although weed suppression was accomplished in all cases.
7. Journal 7 Findings:
In this study by Ewing (2002), the scenario studied was somewhat different than the other papers cited here, which generally focused on weeds competing with vegetable crops. Ewing’s study looked at attempts to restore areas of Pacific Northwest prairies with plantings of the native Idahoe Fescue, which was in competition with other non-native grasses. So, in this study, those non-native grasses were the “weeds” – the unwanted species. Areas to be replanted with nursery-grown Idahoe Fescue were prepared for planting in different ways: a) by burning all existing vegetation; b) by using a herbicide and tilling procedure to remove vegetation; c) by removing all organic matter to impoverish the soil; d) by applying fertilizer; e) by applying a compost mulch. First year results suggested the fertilizer and/or compost mulch was most successful, but over the full three year period of the study it was found that impoverished soil areas and those treated with herbicide and tilling gave the best long term success rates. The previously-mulched areas showed the greatest weed growth at the end of three years. In conclusion, Ewing considered that a combination of impoverished soil and a weed maintenance program would be needed for successful prairie restoration.
8. Journal 8 Findings:
This study by De Cauwer et al (2010) investigated the cumulative effects of 12 years of application of various fertilizers on the size and the composition of the weed seedbank in a maize field. The fertilizers used included dairy cattle slurry, fruit, vegetable and garden waste composts, and nitrogen-based fertilizers. The results were mixed. It was found that whilst the nitrogen-based fertilizers decreased the density of weed seeds found in soil samples (possibly due to lower light levels through the higher and stronger crop growth), areas fertilized with composts or animal slurry were not affected, suggesting that compost application may be useful as part of an integrated strategy to reduce the persistence of the weed seedbank. It was thought that the high temperatures in the compost-making process, plus associated effects of acetic acid, ammonia and microbial activity contributed to these results, which promise a trend towards weed suppressing soils in the longer term.
9. Journal 9 Findings:
This Japanese study by Miyazawa et al (2004) sought to determine if a managed crop rotation system could – with the right combination of conventional and reduced tillage coupled with applications of chemical fertilizers and biocides – maintain weed growth at an acceptable level, yet increase the diversity of weeds present. Results were mixed. However, it appeared that a combination of reduced tillage and applications of manure may cause a reduction in dominant weed species, thereby increasing diversity and possibily encouraging minor weed species.
10. Journal 10 Findings:
Heraux et al (2005) evaluated the effects of a dual approach to weed control. One was the use of Trichoderma virens, a free-living fungus that has been shown to have beneficial effects on plant growth. In the subject project, this was applied incorporated into composted chicken manure (CCM). The second technique was the use of rye as a cover crop. It was found that although results were somewhat mixed – in part due to differing weather conditions over the course of the study period – both of these non-herbicidal techniques exhibited benefits in respect of weed suppression. The researchers admitted however that the treatment processes need refining further before reliable performance could be expected.
Works Cited
Chalkos, D., Kadoglidou, K., Karamanoli, K., Fotiou, C., Pavlatou-Ve, A.S., Eleftherohorinos, I.G., Constantinidou,H-I.A., & Vokou, D. (2010). Mentha spicata and Salvia fruticosa composts as soil amendments in tomato cultivation. Springer Science+Business Media B.V. 2010.
De Cauwer, B., Van Den Berge, K., Cougnon, M., Bulcke, R., & Reheul, D. (2010). Weed seedbank responses to 12 years of applications of composts, animal slurries or mineral fertilisers. Weed Research 50, 425–435.
Ewing, K. (2002). Effects of Initial Site Treatments on Early Growth and Three-Year Survival of Idaho Fescue. Society for Ecological Restoration. Restoration Ecology Vol. 10 No. 2, pp. 282–288.
Heraux, F.M.G., Hallett, S.G., & Weller, S.C. (2005). Combining Trichoderma virens-inoculated compost and a rye cover crop for weed control in transplanted vegetables. Biological Control 34 (2005) 21–26.
Garcia-Martin, A., Lopez-Bellido, R. J., & Coleto, J. M. (2007). Fertilisation and weed control effects on yield and weeds in durum wheat grown under rain-fed conditions in a Mediterranean climate. Weed Research 47, 140–148.
Miyazawa, K., Tsuji, H., Yamagata, M., Nakano, H., & Nakamoto, T. (2004). Response of weed flora to combinations of reduced tillage, biocide application and fertilization practices in a 3-year crop rotation. Weed Biology and Management 4, 24–34 (2004).
Ozores-Hampton, M., Obreza, T. A., & Stoffella, P. J. (2001). Mulching With Composted MSW for Biological Control of Weeds in Vegetable Crops. Compost Science & Utilization, (2001), Vol. 9, No. 4, 352-361.
Ozores-Hampton, M., Obreza, T. A., Stoffella, P. J., & Fitzpatrick, G. (2002). Immature Compost Suppresses Weed Growth Under Greenhouse Conditions. Compost Science & Utilization, (2002), Vol. 10, No. 2, 105-113.
Ozores-Hampton, M., Stoffella, P. J., Bewick, T.A., Cantliffe, D. J., & Obreza, T. A. (1999). Effect of Age of Cocomposted MSW and Biosolids on Weed Seed Germination. Compost Science & Utilization, (1999), Vol. 7, No. 1, 51-57.
