Integrating Mechanical and Cultural Methods for Weed Control in Organic Chickpea

Project Director: Zachariah Miller, Montana State University

Project Overview

Effective weed control remains a challenge in organic systems due to the highly variable efficacy of individual weed management strategies. “Stacking” or utilizing several weed management strategies, such as mechanical and cultural controls, can increase weed control due to crop competitive advantage and the combined effects on efficacy. The Northwest and Plains regions of the US account for approximately 93% of chickpea production, but chickpea yields are often reduced from weeds due to the crop’s slow maturation and short height. This study evaluated two organic chickpea cultivars, chickpea planting date and seeding rate, as well as preemergent weed control methods of shallow tillage and flame weeding, and the resulting effects on crop density, crop yield, and weed biomass over two years.

Farmer Takeaways

Desi chickpea (Black Butte cultivar) had much greater emergence and survival compared to Kabuli chickpea (CDC Orion cultivar) and may be better suited to organic production.
Earlier chickpea planting, increased seeding rate (1.5x rate), and either preemergent weed control (shallow tillage, flame weeding) increased yields individually, and when combined, resulted in the greatest chickpea yield increase.
Effects on weed biomass were variable between years, and the use of individual weed management strategies did not consistently decrease weed biomass. However, combining all three weed management strategies resulted in a high level of weed control.

Project Objectives and Approach

To determine the effects of cultural (cultivar choice, seeding rate, seeding date) and physical (shallow tillage, flaming) integrated weed management (IWM) strategies on chickpea plant stand density, grain yield, and weed biomass.

Field experiments were conducted across two growing seasons (2018 and 2019) at the Western Agricultural Research Center in Corvallis, Montana.
Treatments were applied using a randomized complete block design with split-plots and four replications. Physical weed control and planting date were applied as the whole plot treatments using a factorial combination, and subplots were a factorial combination of the chickpea varieties and seeding rate. Note: due to the performance of the Kabuli type chickpea in 2018, only the Black Butte type was used in 2019.
Planting date was determined by soil temperature, and the early planting date treatment was sown in mid- to late-April each year, with the late planting date occurring 10-14 days later.
Seeding rate treatments were 1x, 1.5x, and 2x, with the standard 1x rate being 43 seeds per square meter.
Shallow tillage occurred approximately 10 days after chickpea planting, prior to chickpea emergence, using sweeps mounted to a toolbar attached to the rear of the tractor.
Flaming occurred approximately 10 days after chickpea planting, prior to chickpea emergence, using a Dragon Vegetable Bed Flamer mounted to the rear of the tractor.
Chickpea plant density was measured three weeks after crop emergence, and weed biomass samples collected when 50% of chickpea plants in the plots had reached flowering.
Chickpea were harvested when seed moisture content was <18% using a plot combine harvester, and chickpea seeds were passed through a 5-mm sieve to remove weed seeds and crop residue.

Key Findings

Desi type chickpea (Black Butte cultivar) performed better than Kabuli type chickpea (CDC Orion cultivar).

Black Butte had superior survival and emergence compared to CDC Orion, which had such low stand density that it was not included in analysis. Black Butte may be better suited for organic production due to its thicker seedcoat which can provide better resistance to fungal diseases and insect feeding.

Chickpea stand density was affected by planting date and seeding rate, but not physical weed control.

Early planting increased chickpea stand density by 1.13-1.48x compared to later planting.
Using a 1.5x seeding rate increased chickpea stand density by 32% compared to the 1x standard rate, but increasing the seeding rate to 2x did not provide additional chickpea stand density increases beyond the 1.5x rate.

Chickpea yield was increased with any of the cultural or physical IWM strategies, and this yield effect was greatest when IWM strategies were combined.

Early chickpea planting had greater yields than late planting, ranging from 3.6x greater in 2018 to 1.8x greater in 2019, likely due to greater crop competitive ability and length of time for flowering and seed formation.
The 1.5x seeding rate increased chickpea yield by 47% compared to the 1x standard rate. A brief comparison of net profits showed that this seeding rate would result in an additional $66 per hectare of seed costs, but a 450 kg per hectare increase in yield, resulting in net profits of $528 per hectare.
Chickpea yields were 47% and 39% greater with shallow tillage and flaming, respectively, compared to control plots.
Integrating early planting, 1.5x seeding rate, and either pre-emergent physical weed control strategy increased chickpea yield 6-fold (318 kg/ha in control plots versus 2,006 kg/ha).

Cultural and physical weed control strategies used individually had inconsistent effects on weed biomass and were likely affected by weather differences between years, but combining weed control strategies significantly reduced biomass.

Weed biomass was similar between planting date treatments in year one, likely due to timing of precipitation that year.
Increasing chickpea seeding rate reduced weed biomass by an average of 25% across both years of the study.
Pre-emergence physical weed control strategies had variable efficacy across years due to weather, and significant reductions in weed biomass were only achieved when these strategies were combined with cultural ones.
The use of early planting, increased seeding rate, and either shallow tillage or flaming all combined resulted in an 84% reduction in weed biomass, supporting the idea of “stacking” practices to achieve high efficacy.

Resources

Miller, Z.J., & Hubbel, K. (2024). Integrating mechanical and cultural methods for weed control in organic chickpea. Weed Science, 72(6), 774-781.

Location

Montana

Collaborators

Kyrstan Hubbel, Montana State University

Region

Northwest, Plains

Topic

Weed Management, Plant Breeding, Varieties, and Seeds

Year Published

2024