Using Abrasive Grit for Weed Management in Field Crops

Agrosystems Geosci & Env

Wortman

et al. 2020

Self Cite

In organic cropping systems, air-propelled abrasive grits can be used to control in-row weeds. If the applied abrasive grit is an approved organic fertilizer, these applications may serve a dual purpose of weed control and crop fertility. Laboratory soil incubations examined the N mineralization rates of several grit types with differing C/N ratios (Agra Grit [crushed walnut shells, 170:1], corncob grit [91:1], Sustane [composted turkey litter, 5.0:1], Phytaboost Plant Food [crushed and pelletized soybean meal, 5.0:1]). A greenhouse study determined plant wheat (Triticum aestivum L.), kale (Brassica napus pabluaria DC), and velvetleaf (Abutilon theophrasti Medik.) growth response in soils amended with these grits. The N mineralization rates varied by grit type, soil, and application rate. The N mineralized from Phytaboost within 56 d was similar among the amounts of N a whereas the amount of N mineralized from Sustane was inversely related to the amount of N applied. Agra Grit and corncob grit immobilized soil N due to their high C/N ratios. In soils amended with Sustane, plant height and biomass were 15-43% and 34-83% greater than for plants grown in soils with Agra Grit, corncob grit, and the nontreated soil. Applications of organic fertilizer as air-propelled grit may improve crop growth; however, if weed control is imperfect, these grits may increase weed growth. Grits with high C/N ratios may immobilize soil available N but not affect plant growth. Abbreviations: DAP, days after planting. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Organic fertilizer abrasive grits increase soil available nitrogen, plant height, and biomass

Carlson

Agrosystems Geosci & Env

Wortman

et al. 2020

Self Cite

“…The weed efficacy of organic fertilizers used as abrasive grits has been previously demonstrated (Braun et al, 2019;Carlson et al, 2018;Forcella et al, 2011;Wortman 2014Wortman , 2015, but this is the first study to report changes in soil fertility and crop-weed competition driven by differences in organic fertilizer grit nutrient analyses and application rates. This is an important finding because it suggests that abrasive weeding technology could be used as a vehicle for improving the precision of in-season fertilizer management in organic cropping systems.…”

Section: Discussionmentioning

confidence: 86%

Abrasive Weeding as a Vehicle for Precision Fertilizer Management in Organic Vegetable Production

Luong

Clay

et al. 2021

hortte

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Abrasive weeding is a nonchemical weed control tactic that uses small, gritty materials propelled with compressed air to destroy weed seedlings. Organic fertilizers have been used successfully as abrasive grits to control weeds, but the goal for this study was to explore the effects of fertilizer grit, application rates, and background soil fertility on weeds, plant available nitrogen (N) uptake, and crop yield. Field trials were conducted in organic ‘Carmen’ sweet red pepper (Capsicum annuum) and organic ‘Gypsy’ broccoli (Brassica oleracea var. italica) and treatments included organic fertilizer grit (8N–0.9P–3.3K vs. 3N–3.1P–3.3K), grit application rates (low vs. high), compost amendments (with and without), and weedy and weed-free controls. Weed biomass was harvested at 84 days and 65 days after transplanting for pepper and broccoli, respectively. Simulated total plant available N (nitrate + ammonium) uptake was measured with ion exchange resin stakes between 7 and 49 days after the first of two grit applications. Produce was harvested at maturity, graded for marketability, and weighed. The higher grit application rate, regardless of fertilizer type, reduced the weed biomass by 75% to 89% for pepper and by 86% to 99% for broccoli. By 5 weeks after the first grit application, simulated plant N uptake was greatest following grit application with the 8% N fertilizer, followed by the 3% N fertilizer, and lowest in the weedy control. The high grit application rate of 8% N fertilizer increased pepper yield by 112% compared with the weedy control, but it was similar to that of the weed-free control. Broccoli was less responsive to abrasive grits, with yield changes ranging from no difference to up to a 36% increase (relative to the weedy control) depending on the application rate and compost amendment. This is the first evidence indicating that the nutrient composition of organic fertilizer abrasive grits can influence in-season soil N dynamics, weed competition, and crop yield. The results suggest that abrasive weeding technology could be leveraged to improve the precision of in-season fertilizer management of organic crops.

“…Abrasive weeding costs could be further reduced by sourcing grits on-farm (as discussed with maize), or by using grits with fertilizer value. Organic fertilizers, including corn gluten meal, soybean meal, greensand and composted turkey manure, have all been used successfully as grits for abrasive weeding (Forcella et al ., 2011; Wortman, 2014; Braun, 2017; Carlson et al ., 2018; Perez-Ruiz et al ., 2018). When applied to soil under controlled conditions at rates typical for abrasive weeding, nitrate is mineralized from organic fertilizers within a 1 month and can increase crop yield (Braun, 2017; Carlson, 2018).…”

Section: Resultsmentioning

confidence: 99%

“…When applied to soil under controlled conditions at rates typical for abrasive weeding, nitrate is mineralized from organic fertilizers within a 1 month and can increase crop yield (Braun, 2017; Carlson, 2018). Under field conditions, organic fertilizer grits can increase soil and plant tissue nitrogen but have rarely increased crop yields relative to walnut shell grits (Braun, 2017; Carlson et al ., 2018). Because organic fertilizer grits were applied during the juvenile phase of crop growth (when soil nitrogen is already in high demand), nitrogen mineralized from the fertilizer may not have been entirely plant available during the first growing season.…”

Section: Resultsmentioning

confidence: 99%

Profitability of abrasive weeding in organic grain and vegetable crops

Wortman

Renew. Agric. Food Syst.

Lambe

et al. 2018

Self Cite

Weed competition, especially within the crop row, limits the productivity and profitability of organic crop production. Abrasive weeding, a mechanical alternative to hand weeding, uses air-propelled grits to control small weed seedlings growing within the crop row. Recent research has demonstrated the successful use of abrasive weeding to reduce weed competition and increase yields in organic maize (Zea mays), tomato (Solanum lycopersicum) and green and red pepper crops (Capsicum annuum), but the profitability of this weed control tactic has not been assessed. Our objective was to determine the profitability of abrasive weeding using empirical yield data from three previously published studies, a range of crop prices and revenues, and a range of costs for wages, grit applicator ownership, tractor use, abrasive grits, and fuel. Results suggest that abrasive weeding was not profitable in organic maize production, and may reduce net income by US$223–3537 ha−1 compared with inter-row cultivation alone for weed control. The cost of abrasive weeding in maize was largely dependent on the cost of abrasive grits and the cost to own a four-row grit applicator (US$736–2105 yr−1). However, abrasive weeding was less expensive than hand weeding, especially as the scale of production increased. Abrasive weeding was profitable in tomato and pepper crops and increased net mean income by US$12,251–33,265 ha−1. However, abrasive weeding was not 100% effective and hand weeding for weed-free conditions was always the most profitable approach to in-row weed management in vegetable crops. The profit potential of the hand-weeded, weed-free treatments demonstrates the importance of weed control in high-value specialty crops–even those grown in plastic mulch film. Despite the profit potential for hand weeding observed here, labor is increasingly difficult to source, retain and afford, and abrasive weeding offers a mechanical alternative with 66% less labor required. Further research is needed to improve the efficacy of abrasive weeding and to reduce the cost of abrasive grits and application.