Organic Fertilizer Abrasive Grits Increase Soil Available Nitrogen, Plant Height, and Biomass

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

Air-Propelled Organic Fertilizer Grits Can be Used to Control Weeds and Provide Nitrogen

Weeds are one of the biggest challenges for organic growers because of the alternative weed control methods. Air-propelled abrasive grit management has been reported to control weed seedlings in corn and soybeans while maintaining yield. This research examined the weed control, corn and soybean yields, nitrogen mineralization, and nitrogen yield responses from grits. The grits used in this research included: Phytaboost Plant Food 7-1-2 (soybean meal), Sustane 8-2-4 and 4-6-4 (turkey litters), and two non-fertilizer grits: Agra Grit (walnut shells) and corn cob meal. Field studies were conducted from 2015 to 2017 in Aurora, SD, Beresford, SD and Morris, MN. Nitrogen mineralization and total nitrogen release from selected grits in two different soils were evaluated in 100 d incubations. The response of corn, wheat, red russian kale and velvetleaf to Sustane 8-2-4, Agra Grit and corn cob meal amended soil was investigated. Agra Grit consistently reduced in-row broadleaf weed biomass in all four site years, whereas when grass weeds were dominant, in-row weed biomass was not reduced with two grit applications. When grit treatments reduced in-row weed density, corn yield increased with fertilizer grits higher than the weed-free check. In-row weed biomass in soybeans was similar among treatments, but when total weed biomass was reduced, the soybean yields were 31 to 55% greater in the grit treatments than weedy checks. Organic fertilizer grits increased soil available nitrogen with 50 to 70% of nitrogen mineralized. Non-fertilizer grits immobilized soil available nitrogen. Plant height and dry weight of wheat, red russian kale, and velvetleaf were greater when the soil was amended with Sustane 8-2-4 compared with Agra Grit, corn cob meal, and no-grit control, although fresh weights and relative greenness were similar among treatments. The use of organic fertilizer grits provide a source for nitrogen for all plants in the targeted area, whereas non-fertilizer grits may immobilize nitrogen. Corn and soybean yields can be increased when two applications of air-propelled grits reduce weed density, regardless the type. Grits may provide nitrogen for the crop but weed control is critical as additional nitrogen also may stimulate weed growth

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

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

Using Abrasive Grit for Weed Management in Field Crops

Abrasive grit, applied at high pressure and directed at plant base, can control weeds and increase yield. We evaluated fertilizer [pelletized turkey (Meleagris gallopavo) litter] and non-fertilizer [walnut (Juglans regia) shell] grits for maize and soybean in-row (IR) weed management. Grits were applied at V1 and V5 of maize, and V1 and V3 of soybean. Between-row weed cultivation was done alone (BR), or in combination with grit (I/B), after grit application. Small weeds (<4 cm) were controlled after grit treatment, but, larger broadleaf weeds, grass weeds (treated when growing points were below ground), and later emerging weeds resulted in IR weed biomass similar between season-long weedy (SLW) and IR treatments by August. In maize, fertilizer and nonfertilizer I/B treatments averaged 44 and 14% greater yields, respectively, than SLW (p<0.01) but each was similar to BR which averaged 23% greater yield (p=0.63). Maize grain had 16% higher N content in the fertilizer I/B treatment than SLW or nonfertilizer I/B (p<0.003). In soybean, I/B increased yield by 17% (p=0.009) over SLW yield, but was similar to the BR increase of 22% (p=0.13). Maize had a greater positive response to fertilizer than nonfertilizer grit, whereas soybean was less influenced by I/B treatment

Abrasive grit application for integrated weed and nitrogen management in organic vegetable cropping systems

Abrasive weed control, or weed blasting, uses sand-blasting technology to propel abrasive grits at weeds, physically destroying their emergent structures. This approach has been successfully tested for use in agronomic crops, though research is needed for horticultural cropping systems. This project aimed to determine the efficacy of weed blasting in vegetable crops and to determine if weed blasting can be combined with mulching to increase the overall effectiveness of each strategy. Five abrasive grit treatments (walnut shell grits, soybean meal fertilizer, Suståne© composted turkey litter fertilizer, a weedy control, and a weed-free control) and four supplemental weed management treatments (straw mulch, biodegradable plastic film, polyethylene plastic film, and a bare soil control) were replicated four times in an organic pepper cropping system near Urbana, IL in 2015 and 2016. Soybean meal, turkey litter, and walnut shell grits, used in conjunction with plastic or bioplastic mulch, all decreased total dry biomass of weeds within the crop row by approximately 80% relative to the weedy control. Total nitrogen availability, measured via ion-resin stakes (PRS probes), decreased by 58% and 55% in soybean meal + bare soil and turkey litter + bare soil plots, respectively, in comparison to the weed free control. There were no significant differences between soybean meal, turkey litter, and the weed free control in plastic, bioplastic, and straw plots. There was no significant decrease in yield compared to the weed free control for turkey litter or walnut shell treatments when combined with either bioplastic or polyethylene mulch or for soybean meal + polyethylene plots. Walnut shell + bioplastic had a significant increase in yield compared to the weedy control. There was no significant difference in fruit quality, measured via BRIX, between grit or mulch treatments, and there was no significant difference of percent of diseased tissue between grit treatments. These results suggest that AWM can function as an alternative weed control strategy in organic farming, potentially improving the effectiveness of existing weed management techniques (e.g., plastic mulch). Abrasive weed management (AWM) also has the possibility to serve as a fertilizer application if organic fertilizers are used as abrasive grits. A separate greenhouse experiment aimed to determine the nitrogen mineralization and plant uptake of different organic fertilizers used as abrasive grits. Five abrasive grit treatments (walnut shell grits, soybean meal fertilizer, Suståne© composted turkey litter fertilizer, a weedy control, and a weed-free control), two application rates (400 g/ plot and 800 g/plot), and two tillage treatments (incorporation of top 5cm of soil and no incorporation) were replicated five times in a greenhouse study using Red Russian kale at University of Illinois at Urbana-Champaign's Plant Care Facility in Urbana, IL in 2016 and 2017. The higher N concentrations of turkey litter and soybean meal contributed to higher N mineralization overall in those treatments. The high rate (800 g/plot) of turkey litter, in particular, outperformed the other treatments in tissue N and yield, which was likely due to the higher N mineralization rate. Incorporation of soil amendments significantly affected soil ammonium concentrations and dry yield weight, suggesting that tillage following grit application could contribute to greater soil availability of N and greater plant uptake. Walnut shell, an effective abrasive grit for weed control, was not as effective as a fertilizer in comparison to soybean meal and composted turkey litter. These results suggest that while soybean meal and turkey litter can function as fertilizer amendments when used for abrasive grit application, walnut shell may not provide the same dual benefit

Propelled Abrasive Grit for Weed Control in Organic Silage Corn

Weed management in organic farming requires many strategies to accomplish acceptable control and maintain crop yields. This 2-yr field study used air propelled abrasive grit for in-row weed control in organically certified silage corn (Zea mays L.). Corncob grit was applied as a single application at corn vegetative growth stages V1 (one true leaf; numbers correspond to number of true leaves at the corn vegetative stage), V3, or V5 (in 2013) and V3, V5, and V7 (in 2014) and in double and triple combinations at these stages. Between-row weed control was accomplished by flaming or cultivation after the last grit application. Grit effects on weed efficacy and silage yield were quantified and compared with hand-weeded and season-long weedy treatments. Grit applications decreased in-row weed biomass by \u3e80% and increased yield up to 250% when compared with the weedy check. Single early applications (V1 and V3) increased yield, with additional treatments decreasing end-of-season weed density and biomass. Single late grit applications (V5 and V7) also decreased weed biomass, but silage yields were reduced compared with hand-weeded and early treatments. Early grit applications may have value for growers to control in-row annual weeds in organic silage corn without soil disturbance

Corncob Grit Application as an Alternative to Control Weeds in Two Crop Production Systems

Weed management is one of the most challenging production problems in organic cropping systems because of limited weed control methods. Grits, derived from agricultural residues, have been demonstrated to control weed seedlings selectively in corn. This research examined weed efficacy and crop yield of an integrated air-propelled abrasive corncob grit (for in-row weed control) at varying timings and frequencies and flame-weeding or cultivation (for between-row weed control) system in two corn production systems. In the first study efficacy of weed control was assessed with this approach in an organic corn silage production system established in Morris, MN in 2013 and 2014. The second study examined efficacy of weed control with this method in a transitioning corn production system established in Aurora, SD in 2013 and 2014. A third study compared efficacy of weed control in both production systems. Measurements included: weed identification, weed density by species, weed biomass (total, broadleaf, grass, in-row, and between-row), plant height, and corn yield (silage and grain). Early applications of abrasive corncob grit resulted in the decrease of 68% and 52% of the total weed biomass in two years of evaluation, and it increased corn silage yield up 26 % when compared to the season long weed control. Late application of corncob grit at the V7 corn growth stage resulted in less weed control. One application at V1 increased corn yield. Additional treatments with or after the V1 treatment improved weed control and may increase yield. Waiting until V5 for grit application resulted in 80% in-row weed biomass reduction, however, there was no positive effect on corn yield. In the second study, in-row weed control resulted in the decrease of 61% of total weed biomass in the transitioning corn production system. Between-row weed control reduced total weed biomass up to 31% for cultivation and 51% for flaming. Even though the application of corncob grit as well as cultivation and flaming at the V5 corn growth stage reduced the total weed biomass, an application of these treatment-combinations at early stages of corn development may potentially achieve better weed control. A treatment combination of in-row weed control and between-row weed control reduced grass biomass. Between-row weed control treatments alone reduced grass weed biomass up to 68% and 61% with flaming treatments. Application of abrasive corncob grit increased corn yield up to 9% compared to the season long weed control. The comparison of these two systems determined that abrasive corncob grit for in-row weed control can reduce weed biomass in both weed control systems and increase silage and corn grain yield

Challenges and Opportunities for Weed Control in Nebraska Popcorn

Weed control in popcorn is challenging with limited herbicide options and popcorn’s perceived sensitivity to herbicides. Understanding the impact of weeds maximizes yield and profit. New herbicide-resistant crops increase chances of drift or misapplication into popcorn, which doesn’t have herbicide-resistant traits. Herbicides that are labeled in popcorn are often only conditionally labeled with reduce rates, warnings, or limited popcorn types. Dent-sterility in popcorn is contingent on the Ga1 gene (Ga1-s), but this system is at risk from Ga1-m field corn introduced from Mexico because it overcomes dent-sterility. This risk is under-assessed as Ga1-m carriers are undocumented and Mexican germplasm usage is increasing for genetic diversity. Experiments conducted 2017-2019 are assessing weed control, herbicide sensitivity, and popcorn purity risk. Chapter 1 outlines the history of popcorn in the United States, current production practices, agronomic challenges, herbicide use in popcorn, and a strategic plan for improving popcorn production. Chapter 2 determines the critical time for weed removal in popcorn produced with and without atrazine/S-metolachlor applied pre-emergence (PRE). Chapter 3 determines weed control options and crop injury potential of five herbicide programs on eight popcorn hybrids. Chapter 4 evaluates the efficacy and crop safety of labeled post-emergence (POST) herbicides for controlling velvetleaf that survived S-metolachlor/atrazine applied PRE in Nebraska popcorn and determines the effect of velvetleaf growth stage on POST herbicide efficacy, popcorn injury, and yield. Chapter 5 examines the effects from drift or misapplication of herbicides to white and yellow popcorn. Chapter 6 models the cross-pollination of popcorn by field corn and investigates the factors influencing contamination and isolation distance. Advisor: Amit J. Jhal

Challenges and Opportunities for Weed Control in Nebraska Popcorn

Weed control in popcorn is challenging with limited herbicide options and popcorn’s perceived sensitivity to herbicides. Understanding the impact of weeds maximizes yield and profit. New herbicide-resistant crops increase chances of drift or misapplication into popcorn, which doesn’t have herbicide-resistant traits. Herbicides that are labeled in popcorn are often only conditionally labeled with reduce rates, warnings, or limited popcorn types. Dent-sterility in popcorn is contingent on the Ga1 gene (Ga1-s), but this system is at risk from Ga1-m field corn introduced from Mexico because it overcomes dent-sterility. This risk is under-assessed as Ga1-m carriers are undocumented and Mexican germplasm usage is increasing for genetic diversity. Experiments conducted 2017-2019 are assessing weed control, herbicide sensitivity, and popcorn purity risk. Chapter 1 outlines the history of popcorn in the United States, current production practices, agronomic challenges, herbicide use in popcorn, and a strategic plan for improving popcorn production. Chapter 2 determines the critical time for weed removal in popcorn produced with and without atrazine/S-metolachlor applied pre-emergence (PRE). Chapter 3 determines weed control options and crop injury potential of five herbicide programs on eight popcorn hybrids. Chapter 4 evaluates the efficacy and crop safety of labeled post-emergence (POST) herbicides for controlling velvetleaf that survived S-metolachlor/atrazine applied PRE in Nebraska popcorn and determines the effect of velvetleaf growth stage on POST herbicide efficacy, popcorn injury, and yield. Chapter 5 examines the effects from drift or misapplication of herbicides to white and yellow popcorn. Chapter 6 models the cross-pollination of popcorn by field corn and investigates the factors influencing contamination and isolation distance. Advisor: Amit J. Jhal