To each their own: case studies of four successful, small-scale organic vegetable farmers with distinct weed management strategies

Article Summary by William Osterholz, Ohio State University

Summary of case studies presented in
"To each their own: case studies of four successful, small-scale organic vegetable farmers with distinct weed management strategies." B. Brown and E.R. Gallandt (2017) Renewable Agriculture and Food Systems.

Four small-scale organic vegetable farms in New England with different weed management approaches were examined (Table 1). Each farmer is well-established with at least 17 yr experience. The researchers interviewed farmers about their weed management philosophy and also measured their weed seedbanks.

Table 1. Characteristics of farms assessed. From Table 1 in Brown and Gallandt (2017).

Mark Guzzi

Mark Guzzi primarily utilizes mechanical cultivation and hand hoeing, with a particular focus on the early “critical period” of weed control. Mark utilizes several cultivators including a Reggie weeder, a rotating set of tines that is moved in and out of the crop rows. He also designs his crop rotation to avoid planting the most weed-sensitive crops in areas with recent heavy seed rain. In years with heavy seed rain he uses a moldboard plow to bury seeds below the germination zone. His philosophy developed largely in response to the weedy condition of his farm when he purchased it. He believes that a better long-term weed management approach may be to exhaust the weed seedbank, but he believes labor and psychological barriers have prevented him from attempting this approach on his farm.

Mark’s farm had the largest weed seedbank of the four farms (3,576 seeds ft^-2). Hairy galinsoga and redroot pigweed dominated his seedbank. Labor management and cost savings were the primary drivers of Mark’s strategy, but some ancillary benefits he identified include possible soil improvement from weed biomass incorporation and providing habitat and food for weed predators such as birds, mice, and beetles. Drawbacks to the strategy included more cost to achieve good weed control in less tolerant crops like carrots or onion, as well as potential disease and pest problems caused by weed presence.

Tom Honigford

Tom Honigford seeks to prevent any weed seed production on his farm, and relies on mechanical cultivation every 10-14 days while crops are small, and in larger crops switches to scuffle hoeing and hand pulling to control remaining weeds. He utilizes six different cultivators suited to different conditions which provides flexibility to achieve weed control in a range of situations. Short-term cover crops are frequently used in his rotations, with the goal of incorporating weeds before they can produce seed. His philosophy stems from his appreciation for “clean” fields and his observation that an early investment in labor was paying off in lower weed pressure.

Tom had the smallest weed seedbank (285 seed ft^-2) of the four farms. The most abundant weed in his

seedbank was purslane as it can survive and produce seeds after cultivation. Tom is now transporting this weed out of his fields by hand. Although Tom’s seedbank management strategy required much labor in the early years, it has led to a dramatic reduction in weed populations and reductions in hand weeding requirements. He notes that he has achieved long-term profitability, showing the economic sustainability of frequent cultivations. An additional benefit noted by Tom is that the lack of weed competition with his crops has allowed him to skip applications of mid-season fertilizer, while a potential drawback he noted was that his frequent cultivations may negatively impact soil quality.

Dave Colson

Weed control on most of the crops on Dave Colson’s farm is provided by black plastic mulch, which is applied using a single bed plastic mulch applicator. The mulched beds are usually not hand weeded. Weed control in paths is provided by a toolbar with a set of sweeps, and hand hoeing is done along plastic edges. Crop rotation design takes into account the weed seedbank, where for weed sensitive crops he increases the number of fallow periods in the preceding year. However if the weed seedbank is sufficiently small he prioritizes building soil fertility with legumes. His philosophy developed after he started using black plastic to provide additional heat to heat-loving crops. He expanded his use to crops like early brassicas to save labor for planting and weeding direct-seeded crops.

Dave has a moderately high weed seedbank (1,761 seeds ft^-2) which could be a result of weeds at plastic edges or in planting holes escaping control. Some ancillary benefits of the plastic mulch include conservation of soil moisture, and possibly reducing the weed seedbank by stimulating germination under the plastic mulch where weeds die. Drawbacks noted by Dave include the environmental cost of throwing away plastic every year, as well as the challenge of keeping tracking of which beds have been covered with plastic and are ready for transplanting.

Tom Roberts

Tom Roberts utilizes hay and tree leaf mulches for most crops. Mulch is applied by hand when crops are large enough to avoid being covered. Mulching timing depends on the crop, with some mulched immediately after transplanting and others allowed to grow prior to mulching, during which time they are hand weeded. Weeds pushing through mulch are also hand weeded. A flail mower is used to produce finely chopped mulch on the farm, making sure to cut hay before seed production. Leaves collected by the nearby municipality are also used for mulch. A mix of summer cover crops and bare fallows is used every fourth year to reduce the weed seedbank, while winter cover crops are rarely used due to the high soil coverage provided by the mulch. The availability of mulch to the farm was a primary reason Tom developed this strategy. The necessity to increase water retention was a major factor which justified the additional hand labor needed to mulch.

Tom’s seedbank was small (665 seeds ft^-2), suggesting high effectiveness of his natural mulching. An important additional benefit of this strategy noted by Tom is the increased water conservation provided by the natural mulch. He also identified increased SOM and soil quality as a benefit, which is allowing him to gradually reduce the amount of compost applied to his crops. A drawback of the natural mulch is cooler soils, but this is minimized by not applying mulch to heat-loving crops until July. The biggest drawback is the high labor requirement to cut and apply the mulch, and the land required to grow the mulch which Tom estimated is 5 to 10 times the area of the mulched beds.

The researchers note that each farmer presented distinct strategies consistent with their farm’s goals. Mark Guzzi achieves his goal of near-term labor and cost savings with the critical period strategy. Tom Honigford has reduced his weed seedbank with the zero seed rain approach, reducing the need for seasonal workers. Dave Colson saves weeding labor during his busy planting season with black plastic mulch. Finally, Tom Roberts uses more labor to implement his natural mulch strategy which is justified by the soil benefits.

Reference: Brown, B., and E.R. Gallandt. 2017. To each their own: case studies of four successful, small-scale organic vegetable farmers with distinct weed management strategies. Renewable Agriculture and Food Systems pp 1-7. Full article available here.