**Author details**

#### Katsumi Ohta

Address all correspondence to: ohta@life.shimane-u.ac.jp

Department of Agricultural and Forest Sciences, Shimane University, Matsue, Japan

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**Chapter 5**

**Provisional chapter**

**Using Abrasive Grit for Weed Management in Field**

**Using Abrasive Grit for Weed Management in Field** 

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,

**Keywords:** maize (Zea mays), soybean (Glycine max), air-propelled grit, weed control

The number and acreage of organic certified farms across the United States has increased [1] due to expanding organic foods sales [2], which has created premiums for organically grown commodities [3, 4] and alternative income streams for farmers. Crop fertility and weed

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

DOI: 10.5772/intechopen.76875

Michael Carlson, Frank Forcella, Sam Wortman and

whereas soybean was less influenced by I/B treatment.

Michael Carlson, Frank Forcella, Sam Wortman and

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.76875

**Crops**

**Crops**

Sharon A. Clay

Sharon A. Clay

**Abstract**

**1. Introduction**

#### **Using Abrasive Grit for Weed Management in Field Crops Using Abrasive Grit for Weed Management in Field Crops**

DOI: 10.5772/intechopen.76875

Michael Carlson, Frank Forcella, Sam Wortman and Sharon A. Clay Michael Carlson, Frank Forcella, Sam Wortman and Sharon A. Clay

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.76875

#### **Abstract**

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.

**Keywords:** maize (Zea mays), soybean (Glycine max), air-propelled grit, weed control

#### **1. Introduction**

The number and acreage of organic certified farms across the United States has increased [1] due to expanding organic foods sales [2], which has created premiums for organically grown commodities [3, 4] and alternative income streams for farmers. Crop fertility and weed

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

management, within the confines of the certified organic regulations [5], are major concerns in organic production systems, as methods other than synthetic chemicals must be utilized. Alternative organic-approved nutrient sources include manures [6–9] and seed meals [9–11], when derived from certified organic materials.

**2. Air propelled abrasive grit influence on in-row weed control and** 

Two grits, made from materials that are approved for organic production and that differ in fertilizer value, were used for in-row application and control of weeds. Sustane® (Sustane Corp., Cannon Falls, MN), is made from pelletized aerobically composted turkey litter [71],

shells, which has a high C:N ratio with little immediate nitrogen availability, provided a low N content comparison. Sustane and Agra Grit products have a hardness value of 3 on the

Maize and soybean were planted from 2015 to 2017 in organic certified production fields at the SDSU Southeast Research Farm (Beresford, SD), in a non-certified transition area at the SDSU Research Field Station at Aurora, SD; and in conventionally managed fields at the at the Swan Lake Research Farm (Morris, MN). Soil types were silt loam complexes (Morris and

Varieties used, relative maturity (RM), planting and harvest dates varied by year and location (**Table 1**). Swan Lake was the northernmost location and used shorter RM varieties. Southeast was the southernmost location and used longer RM varieties. Maize was seeded at 3.5-cm depth, when soil temperatures were 14°C. Soybean seeding rate varied by location and year (**Table 1**) and was planted at 2.4-cm depth when soil temperatures were 18°C. Row spacing was 0.76 m with four crop rows per treatment (~3-m width). Plot length varied from

Sustane 8-2-4 and Agra Grit were applied in all trials. In-row (IR) grits were applied twice, at the V1 and V5 maize growth stages, and the V1 and V3 soybean growth stages (**Table 1**). About 800 kg ha−1 of grit was used for each application, which was applied using a propelled abrasive grit applicator [PAGMan] that sprays four rows simultaneously, with a nozzle on each side of the row [69, 70]. Distance of the nozzle tip to the base of the maize plants was between 10 and 15 cm, at a 45° contact angle. Spray pressure was 690 kPa and tractor speed was 2.5 km hr.−1. After the final grit treatment each year, a single cultivation was used for between-row (BR) weed control using a John Deere® 866 spring tine cultivator at 5 km hr.−1. In addition, other treatments all years included a single between-row cultivation, as described previously, to determine yield potential with only cultivation, season-long weedy (SLW) to estimate yield in nontreated conditions, and weed-free (hand-weeded weekly until canopy

Weed species and density were recorded in each plot prior to and about 1 week after final grit applications. In mid-July to early September depending on crop and year (**Table 1**), weeds,

closure) to estimate maximum yield potential under weed-free conditions.

O). Agra Grit (AgraLife), made from walnut

Using Abrasive Grit for Weed Management in Field Crops

http://dx.doi.org/10.5772/intechopen.76875

55

O5 -K<sup>2</sup>

Mohs scale of mineral hardness and varied in size from 0.56 to 0.85 mm.

**crop yield**

*2.1.1. Grits*

**2.1. Materials and methods**

*2.1.2. Field experiments*

3 to 9 m.

and had a fertilizer grade of 8-2-4 (N-P2

Beresford) and a silty clay loam at Aurora.

Weed control repeatedly has been ranked as very to extremely problematic [12–14] and as a top research priority [15] in organic producer surveys. Flexible systems that rely on cultural and mechanical methods are needed to prevent the creation of specialized weed communities [16, 17]. Cultural methods enhance the crop's competitive ability [16], reducing weed impact. Methods include alternating crops that vary in seasonal growth, fertilizing differentially [18], or speeding canopy closure by planting in narrow rows or at high densities [19–24]. Dense cover crop mulches, such as those created by rye grass (*Lolium* sp.) or hairy vetch (*Vicia villosa*), suppress weeds [25–29], although these may become major weed problems or immobilize N, negatively impacting yield, if not carefully managed [26, 28].

The most important time for weed control is during the early growth stages of a crop, also known as the critical weed free period, so that yield is not reduced [30–39]. Careful timing of physical and mechanical weed control operations [40–42], including deeper tillage or seedbed preparation that disturbs newly emerging weed seedlings (i.e. stale seedbed) [43–45] can provide weed control and lower in-season weed density [46, 47]. Burying the weeds to at least 1 cm deep, through rotary hoeing or rod weeding, or mowing the weeds at the surface also provides control [48, 49].

Cultivation, or flaming at high temperatures [50], are effective methods to control betweenrow weeds, however, in-row weed control is still a problem for organic growers [51]. In-row weeders, including harrows, finger and torsion weeders, and weed blowers, have been developed [52–55]. However, crop burial or injury [56] can result in yield reduction [57] so that accurate steering and slow driving are needed to minimize crop damage [51]. Despite advances in physical weed management, organic growers are not satisfied with the tools available nor the amount of weed suppression achieved [58]. Additional methods would provide alternatives to support these 'traditional' weed control techniques [51, 59–61].

Air-propelled abrasive grit application for weed control by tissue abrasion was proposed by Nørremark et al. [62]. Numerous types of grits made from agricultural (e.g., maize cobs and walnut shells), non-agricultural (e.g., sand), and organic fertilizer (e.g., soybean meal and corn gluten meal) materials controlled weeds in greenhouse and field settings [63–70] when sprayed at high pressure (800 kPa). In the field, two or three in-row grit applications, applied from V1 to V5 growth stage of maize, could reduce weeds and increase grain or silage yields [65, 69, 70].

Although Forcella [66] demonstrated that soybean could tolerate grit applications after the cotyledon (VC) growth stage, the influence of in-row grit application on weed control has not been field tested in this crop. In addition, organic fertilizers, such as pelletized turkey litter [71], have not been tested as abrasive grits for weed control in maize or soybean field studies. The hypotheses of this study were that 1) grits derived from different sources would result in similar weed control when applied at early crop/weed growth stages; and 2) crop yield would be increased by grits containing nitrogen [68, 72, 73].
