Organic farmers need a diverse toolbox of weed management tactics. Tillage is currently the most common method of weed management in organic systems (Baker and Mohler, 2015), but wet soil conditions, crop growth stage, and overuse can limit its effectiveness. For example, if rotary hoeing is used too frequently, it can cause crop injury and a decline in yield, although too few passes can also cause yield loss due to poor weed control (Kluchinski and Singer, 2005; Leblanc and Cloutier, 2001; Taylor et al., 2012). Because tillage disturbs the soil surface, there is a potential for soil degradation including the loss of soil aggregate structure and organic matter, and increased erosion (Munkholm et al., 2013). Tillage can also increase weed seedbank density by distributing and burying newly shed weed seeds; similarly, soil disturbance can bring buried weed seeds near the surface to facilitate germination (Bond and Grundy, 2001; Melander and Rasmussen, 2000).
Current alternatives to tillage for weed management in organic systems include mulching with plastic films, straw, or cover crops and organic herbicides, mowing, flame weeding, laser treatment (Mathiassen et al., 2006), hot oil microdosing (Zhang et al., 2012), and steam and hot water (Kristoffersen et al., 2008). Mulching can provide season-long weed control along with improved crop performance through increases in available water and enhanced efficiency of irrigation systems (Sarkar et al., 2007; Sarkar and Singh, 2007). Mulching with straw or cover crop residues increases soil moisture and reduces weed growth, but it is usually less effective than black plastic mulch film for weed management (Anzalone et al., 2010). The volume of organic mulch required for effective weed management can be cost-prohibitive and logistically challenging to transport if not produced on or near the farm. Organic mulch residues are biodegradable, but decomposition during the growing season can result in untimely microbial immobilization of essential plant nutrients (Bond and Grundy, 2001). Moreover, straw and hay mulches can carry weed seeds and increase seed bank density (Schonbeck, 1999).
Plastic and biodegradable plastic mulch films are commonly used for weed management in vegetable production, but weeds can emerge through any uncovered space, including crop holes or tears in the plastic (Schonbeck, 1999; Wortman, 2015). Plastic films increase soil temperature (Lamont, 2005) and increase water use efficiency (Moreno and Moreno, 2008), especially when integrated with drip or subsurface drip irrigation (Anzalone et al., 2010). The biggest drawback to plastic mulch film is that it must be removed from the field after harvest, and disposal has economic and environmental consequences (Kasirajan and Ngouajio, 2012; Miles et al., 2012).
Concerns about plastic mulch film disposal have led to the development of biodegradable alternatives. Biodegradable plastic mulch film can degrade into nontoxic compounds, although more stable degradable polymers may remain in the soil as microfragments for extended periods of time (Fontanelli et al., 2013; Kasirajan and Ngouajio, 2012; Miles et al., 2012). Most biodegradable plastic mulches provide similar agronomic services as polyethylene plastic, though polyethylene is more effective for increasing soil temperature (Moreno and Moreno, 2008). The main barrier to on-farm adoption of biodegradable mulch films is the higher cost, which is a result of the higher costs of raw materials (Fontanelli et al., 2013). Paper mulch (e.g., WeedGuardPlus; SunShine Paper, Aurora, CO) is the only biodegradable mulch currently allowed as a soil input on U.S. Department of Agriculture (USDA) certified organic farms, but it can be difficult to install, is susceptible to damage from high winds, and often degrades before the end of the growing season, leading to weed establishment (Anderson et al., 1996; Anzalone et al., 2010; Schonbeck, 1999).
Despite recent innovations in nonchemical weed management tactics, flame weeding remains among the most common alternatives to tillage on organic farms (Baker and Mohler, 2015). Flame weeding with propane gas does not disturb the soil, which can help to minimize weed seed germination; however, flaming has been shown to increase germination of some weed species (Ascard, 1995; Bond and Grundy, 2001; Taylor et al., 2012). Flame weeding can be done in wet soils, and application timing is generally more flexible than tillage because it does not require soil disturbance. One drawback of flame weeding is the potential for crop injury and yield loss when applied in the row (Ulloa et al., 2010). However, crops like garlic (Allium sativum) can tolerate up to three flame treatments for in-row weed management without any reduction in productivity (Chehade et al., 2018). Despite its effectiveness in field crops, flame weeding cannot be used to manage in-row weeds (e.g., those in the crop hole) in mulched or plasticulture vegetable production because the mulch or films could catch fire or melt.
Abrasive weeding is a relatively new approach to organic weed management that uses compressed air to propel agricultural grits, including fertilizers, at weed seedlings to physically destroy emerged structures (Forcella, 2009a; Wortman, 2014). A diverse range of materials have demonstrated effectiveness as grits for abrasive weeding, including granulated corn gluten meal, corn cobs, greensand fertilizer, walnut shells, and soybean meal (Wortman, 2014). Abrasive weeding applications may also be used to supplement in-season crop nutrition if organic fertilizers (e.g., soybean meal) are used as the grit source, which could lead to additional gains in crop growth, yield, and profitability of this weed management tactic. Moreover, delaying plant available soil nitrogen early in the growing season could shift the outcome of crop-weed competition in favor of crops and better synchronize nutrient mineralization with peak crop demand (Liebman and Davis, 2000; Wortman et al., 2011).
Abrasive weeding has been studied in corn and soybean (Carlson et al., 2018; Erazo-Barradas et al., 2019), but less research has been conducted in vegetable crops considering interactions with unique cropping system attributes such as mulch films (Wortman, 2014, 2015). Although abrasive weeding has been used successfully to manage weeds in plasticulture tomato and pepper (Wortman, 2015), it is not known if this technology is compatible with other types of agricultural mulch or if it is suitable for use in systems without mulch. There are also questions about the effects of abrasive weeding on crop health. Stem and leaf injury after abrasive weeding in vegetables may increase susceptibility to disease by providing an entry point for pathogens (Wortman, 2014), but that potential risk has not been quantified. Lastly, the opportunity for integrating nitrogen and weed management with abrasive grit applications has been proposed (Forcella et al., 2011), but actual soil nitrogen contributions and potential plant nitrogen uptake from abrasive weeding have not been quantified.
The overall aim of this study was to determine the effectiveness of abrasive weeding in organic sweet red pepper (Capsicum annuum L. ‘Carmen’) production. Specific objectives were to 1) quantify the effects of different grit types on weed suppression, disease severity, soil nitrogen availability and potential crop uptake, and crop yield and 2) determine the compatibility of abrasive weeding with different types of mulch for nonchemical, in-row weed management.
Anderson, D.F., Garisto, M.-A., Bourrut, J.-C., Schonbeck, M.W., Jaye, R., Wurzberger, A. & DeGregorio, R. 1996 Evaluation of a paper mulch made from recycled materials as an alternative to plastic film mulch for vegetables J. Sustain. Agr. 7 1 1509 1516
Anzalone, A., Cirujeda, A., Aibar, J., Pardo, G. & Zaragoza, C. 2010 Effect of biodegradable mulch materials on weed control in processing tomatoes Weed Technol. 24 3 1509 1516
Baker, B.P. & Mohler, C.L. 2015 Weed management by upstate New York organic farmers: Strategies, techniques and research priorities Renew. Agr. Food Syst. 30 5 1509 1516
Braun, E.E. 2017 Abrasive grit application for integrated weed and nitrogen management in organic vegetable cropping systems. University of Illinois at Urbana–Champaign, Urbana, MS Thesis
Carlson, M., Forcella, F., Wortman, S.E. & Clay, S.A. 2018 Using abrasive grit for weed management in field crops. In: M.A. El-Ewawi (ed.). Physical properties and physical methods for stimulation of plant and mushroom development. InTech Open, Rijeka, Croatia. 8 July 2019. <https://www.intechopen.com/books/physical-methods-for-stimulation-of-plant-and-mushroom-development/using-abrasive-grit-for-weed-management-in-field-crops>
Chehade, L.A., Fontanelli, M., Martelloni, L., Frasconi, C., Raffaelli, M. & Peruzzi, A. 2018 Effects of flame weeding on organic garlic production HortTechnology 28 502 508
Döring, T.F., Brandt, M., Heß, J., Finckh, M.R. & Saucke, H. 2005 Effects of straw mulch on soil nitrate dynamics, weeds, yield and soil erosion in organically grown potatoes Field Crops Res. 94 2 1509 1516
Duczek, L.J., Jones-Flory, L.L., Reed, S.L., Bailey, K.L. & Lafond, G.P. 1996 Sporulation of Bipolaris sorokiniana on the crowns of crop plants grown in Saskatchewan Can. J. Plant Sci. 76 4 1509 1516
Erazo-Barradas, M., Friedrichsen, C.N., Forcella, F., Humburg, D. & Clay, S.A. 2019 Propelled abrasive grit applications for weed management in transitional corn grain production Renew. Agr. Food Syst. 34 1 1509 1516
Flavel, T.C. & Murphy, D.V. 2006 Carbon and nitrogen mineralization rates after application of organic amendments to soil J. Environ. Qual. 35 1 1509 1516
Fontanelli, M., Raffaelli, M., Martelloni, L., Frasconi, C., Ginanni, M. & Peruzzi, A. 2013 The influence of non-living mulch, mechanical and thermal treatments on weed population and yield of rainfed fresh-market tomato (Solanum lycopersicum L.) Span. J. Agr. Res. 11 3 1509 1516
Forcella, F., James, T. & Rahman, A. 2011 Post-emergence weed control through abrasion with an approved organic fertilizer Renew. Agr. Food Syst. 26 1 1509 1516
Gale, E.S., Sullivan, D.M., Cogger, C.G., Bary, A.I., Hemphill, D.D. & Myhre, E.A. 2006 Estimating plant-available nitrogen release from manures, composts, and specialty products J. Environ. Qual. 35 6 1509 1516
Granke, L.L., Quesada-Ocampo, L., Lamour, K. & Hausbeck, M.K. 2012 Advances in research on Phytophthora capsici on vegetable crops in the United States Plant Dis. 96 11 1509 1516
Kasirajan, S. & Ngouajio, M. 2012 Polyethylene and biodegradable mulches for agricultural applications: A review Agron. Sustain. Dev. 32 2 1509 1516
Kluchinski, D. & Singer, J.W. 2005 Evaluation of weed control strategies in organic soybean production. Crop Mgt. 4(1)
Knowles, T.C., Hipp, B.W., Graff, P.S. & Marshall, D.S. 1993 Nitrogen nutrition of rainfed winter wheat in tilled and no-till sorghum and wheat residues Agron. J. 85 4 1509 1516
Kristoffersen, P., Rask, A.M. & Larsen, S.U. 2008 Non-chemical weed control on traffic islands: A comparison of the efficacy of five weed control techniques Weed Res. 48 2 1509 1516
Krupinsky, J.M., Bailey, K.L., McMullen, M.P., Gossen, B.D. & Turkington, T.K. 2002 Managing plant disease risk in diversified cropping systems Agron. J. 94 2 1509 1516
Leblanc, M.L. & Cloutier, D.C. 2001 Susceptibility of dry edible bean (Phaseolus vulgaris, cranberry bean) to the rotary hoe Weed Technol. 15 2 1509 1516
Liebman, M. & Davis, A.S. 2000 Integration of soil, crop and weed management in low-external-input farming systems Weed Res. 40 1 1509 1516
Liu, X.J., Wang, J.C., Lu, S.H., Zhang, F.S., Zeng, X.Z., Ai, Y.W., Peng, S.B. & Christie, P. 2003 Effects of non-flooded mulching cultivation on crop yield, nutrient uptake and nutrient balance in rice–wheat cropping systems Field Crops Res. 83 3 1509 1516
Melander, B. & Rasmussen, K. 2000 Reducing intrarow weed numbers in row crops by means of a biennial cultivation system Weed Res. 40 2 1509 1516
Miles, C., Wallace, R., Wszelaki, A., Martin, J., Cowan, J., Walters, T. & Inglis, D. 2012 Deterioration of potentially biodegradable alternatives to black plastic mulch in three tomato production regions HortScience 47 1270 1277
Moreno, M.M. & Moreno, A. 2008 Effect of different biodegradable and polyethylene mulches on soil properties and production in a tomato crop Scientia Hort. 116 3 1509 1516
Nyiraneza, J., N’Dayegamiye, A., Chantigny, M.H. & Laverdière, M.R. 2009 Variations in corn yield and nitrogen uptake in relation to soil attributes and nitrogen availability indices Soil Sci. Soc. Amer. J. 73 1 1509 1516
Page, E.R., Tollenaar, M., Lee, E.A., Lukens, L. & Swanton, C.J. 2010 Shade avoidance: An integral component of crop–weed competition Weed Res. 50 4 1509 1516
Pérez-Ruiz, M., Brenes, R., Urbano, J.M., Slaughter, D.C., Forcella, F. & Rodríguez-Lizana, A. 2018 Agricultural residues are efficient abrasive tools for weed control Agron. Sustain. Dev. 38 2 18
Ponce, R.G., Zancada, C., Verdugo, M. & Salas, L. 1996 Plant height as a factor in competition between black nightshade and two horticultural crops (tomato and pepper) J. Hort. Sci. 71 3 1509 1516
Roe, N.E., Stoffella, P.J. & Bryan, H.H. 1994 Growth and yields of bell pepper and winter squash grown with organic and living mulches J. Amer. Soc. Hort. Sci. 119 1193 1199
Sarkar, S. & Singh, S.R. 2007 Interactive effect of tillage depth and mulch on soil temperature, productivity and water use pattern of rainfed barley (Hordium vulgare L.) Soil Tillage Res. 92 1 1509 1516
Sarkar, S., Paramanick, M. & Goswami, S.B. 2007 Soil temperature, water use and yield of yellow sarson (Brassica napus L. var. glauca) in relation to tillage intensity and mulch management under rainfed lowland ecosystem in eastern India Soil Tillage Res. 93 1 1509 1516
Schonbeck, M.W. 1999 Weed suppression and labor costs associated with organic, plastic, and paper mulches in small-scale vegetable production J. Sustain. Agr. 13 2 1509 1516
Taylor, E.C., Renner, K.A. & Sprague, C.L. 2012 Organic weed management in field crops with a propane flamer and rotary hoe Weed Technol. 26 4 1509 1516
Ulloa, S.M., Datta, A., Malidza, G., Leskovsek, R. & Knezevic, S.Z. 2010 Timing and propane dose of broadcast flaming to control weed population influenced yield of sweet maize (Zea mays L. var. rugosa) Field Crops Res. 118 3 1509 1516
Wortman, S.E. 2014 Integrating weed and vegetable crop management with multifunctional air-propelled abrasive grits Weed Technol. 28 1 1509 1516
Wortman, S.E. 2015 Air-propelled abrasive grits reduce weed abundance and increase yields in organic vegetable production Crop Prot. 77 157 162
Wortman, S.E., Kadoma, I. & Crandall, M.D. 2015 Assessing the potential for spunbond, nonwoven biodegradable fabric as mulches for tomato and bell pepper crops Scientia Hort. 193 209 217
Wortman, S.E., Forcella, F., Lambe, D., Clay, S.A. & Humburg, D. 2018 Profitability of abrasive weeding in organic grain and vegetable crops Renewable Agr. Food Systems 1 6
Zhang, Y., Staab, E.S., Slaughter, D.C., Giles, D.K. & Downey, D. 2012 Automated weed control in organic row crops using hyperspectral species identification and thermal micro-dosing Crop Prot. 41 96 105
Zhang, H., Miles, C., Ghimire, S., Benedict, C., Zasada, I. & DeVetter, L. 2019 Polyethylene and biodegradable plastic mulches improve growth, yield, and weed management in floricane red raspberry Scientia Hort. 250 371 379
Zhu, J., Tremblay, N. & Liang, Y. 2012 Comparing SPAD and atLEAF values for chlorophyll assessment in crop species Can. J. Soil Sci. 92 4 1509 1516