- Vegetables: beans, cucurbits, sweet corn
- Crop Production: conservation tillage
- Education and Training: on-farm/ranch research, participatory research, workshop
- Pest Management: cultural control, integrated pest management, mulches - killed, weed ecology
- Production Systems: agroecosystems
- Soil Management: green manures, soil quality/health
Our research investigated the impact of strip tillage (ST) and cover crops on weeds, insects, crop yield and profitability in sweet corn, snap beans, and cucurbit crops. In most cases, ST maintained yields and reduced costs relative to full-width tillage, resulting in economic benefits. Contrary to expectations, use of rye cover cropping provided relatively few measurable benefits, and in some cases resulted in losses in yield and profitability. Publications and presentations from our work have reached over 1000 growers, who are now better equipped to decide whether and how to adopt ST on their farms.
Strip-tillage in vegetable crops has the potential to provide multiple direct benefits relative to conventional tillage systems, including: 1) improvements in soil physical, chemical and biological properties for optimal crop growth; 2) reductions in energy- and labor- use due to fewer tractor passes; 3) protection of vulnerable vegetable seedlings from intense wind and rain events; 4) reductions in disease and physical damage to plants through reduced rain-splash and crop-soil contact; 5) more timely planting under wet field conditions; 6) enhancement of beneficial organisms such as predaceous insects and earthworms; and 7) improvement in nutrient and pesticide use-efficiency through reduced run-off and leaching.
In recent years, vegetable growers have observed an increase in extreme rain and wind events, and have expressed interest in reduced tillage systems to help protect their vulnerable soils and crops. Given predicted increases in climate variability, the need for resilient cropping systems has never been more important. Innovative vegetable growers have begun experimenting with the use of cover crops grown in combination with reduced tillage for wind protection. For example, in Oceana and Mason counties in W. Michigan, strip tillage in combination with winter wheat cover crops has gained popularity as a means to protect stand losses of vulnerable carrot seedlings.
Increases in the cost of diesel fuel and energy-intensive agrichemicals like N fertilizers provide increasing incentives for growers to reduce tractor passes in their fields. Strip-tillage typically involves 2 tractor passes for crop establishment, where 5 or more passes are common under conventional tillage systems. Strip-tillage also facilitates placement of fertilizer in the strip at depths where the plant needs it most, thus improving fertilizer-use efficiency.
In winter squash and pumpkin production, fruit scarring and staining is a problem that often results in reductions in marketable yield. Growers have attempted no-till to address this problem, but have observed poor stand establishment and costly delays in emergence and growth of crops under no-till systems. Strip-tillage facilitates improved seed-bed preparation and soil warming, thus addressing stand-establishment problems while maintaining benefits of surface residue for reducing fruit scarring. Surface residues present under strip-tillage systems may also reduce the dispersal of soil borne propagules of plant pathogens onto developing fruit and leaves. In recent years, diseases such as Phytophthora blight have become a major problem for vegetable growers. If reduced tillage systems can suppress these diseases, they would provide a big boost to farm profits.
Although strip-tillage has the important potential benefits outlined above, additional information is needed to 1) understand the effects of reduced tillage and cover crops on pests of vegetables, and 2) develop complementary management practices to optimize strip-tillage systems for crop productivity. When asked about strip-tillage, many growers express concern that this practice may make weed, insect or disease management more challenging. These are legitimate concerns that must be addressed before growers will invest in equipment and take the risk associated with changing their current practices. Successful adoption of strip-tillage depends on understanding pest responses, and adjusting pest management practices including rates, types, and timings of pesticides, as well as complementary practices such as cover crops and stale seed beds to reduce the risk of crop yield losses in these systems.
Weed management is particularly challenging in reduced tillage vegetable production systems and is often cited as the major constraint to adoption. When tillage is reduced, many weed species that were previously controlled through soil disturbance become more problematic. Weed populations in the undisturbed between-row environments may shift over time towards more winter annual and perennial weeds. On the other hand, summer annual weeds may be less problematic in undisturbed areas, since weed seeds will not experience germination stimuli associated with tillage (e.g. light, nitrates), and new seeds will not be readily brought to the soil surface. Strip tillage also makes it possible to take greater advantage of surface residues for inhibiting weed seed germination through reductions in light penetration, physical obstruction, or release of allelochemicals.
By definition, sustainability of alternative management practices can only be adequately assessed through long-term studies. While such studies exist for many agronomic cropping systems, relatively few have examined long-term impacts of management practices in vegetable cropping systems. Results from existing studies demonstrate the potential value of reduced tillage for reducing energy costs, improving vegetable quality, and improving soils. However, these studies have generally concluded that more work needs to be done to develop longer-term reduced tillage systems for vegetable crops, adopt research to different agro-ecological zones, and improve complementary management practices, including weed management.
Strip-tillage effects on crop yields and input costs. The practical potential benefits of strip-tillage for selected field and vegetable crops have been well summarized in several extension bulletins (e.g. Al-Kaisi and Hannah 2008; Luna and Staben 2003; Myers et al. 2008). For field crops like corn and soybean, strip tillage has been observed to produce equivalent yields to moldboard plowing and higher yields than no-till under many soil conditions (Al-Kaisi and Hannah 2008). Yield improvements relative to no-till in these systems are often attributed to improved pre-plant soil warming and drying. Strip-tillage also allows deep banding of fertilizers during tillage operations and hence improvements in fertilizer use efficiency relative to no-till, and reductions in tillage costs relative to conventional tillage. Overall, the number of tractor passes in strip-till systems is typically reduced to 2, where 2-3 passes are required in no-till systems, and 5 or more required for conventional tillage (broadcast P and K; chisel plow; knife in N; field cultivate; plant).
Research comparing strip-tillage and conventional tillage in vegetable crops is limited, but promising results have been demonstrated in several regions and cropping systems. Studies with strip-tillage systems in sweet corn have generally reported equivalent yields with reduced costs and hence increased profitability. For example, in Oregon, strip-tillage yields have generally been equivalent to conventional tillage, with approximately $15/A savings in tillage costs (Luna and Staben 2003). Similarly, in NY, strip-tilled sweet corn has been reported to produce equivalent yields with reduced input-costs compared to conventional tillage (Rangarajan et al. 2006).
Strip-tillage effects on beneficials and crop pests. Several studies have documented increases in beneficial organisms associated with strip-tillage systems. Untilled strips with residue or live cover crops provide alternative resources and microhabitat for beneficial insects such as predators and parasitoids (Letourneau, 1990; Landis et al., 2000; Wilkinson & Landis, 2005; Schellhorn & Sork, 1997). In North Carolina, a long-term study comparing conventional and strip tillage treatments in tomato production systems, reported a 31-fold increase in earthworm populations under strip-tillage (Overstreet et al. 2010). In Oregon, Luna and Staben (2003) report increases in beneficial earthworm and carabid beetle populations in strip-tilled sweet corn relative to conventional tillage.
Strip-tillage effects on insect and nematode pests depend on the specific crop, pest and climate. In some cases, reductions in insect pests have been observed under reduced tillage. For example, a recent study in strip-tilled versus conventionally tilled cotton production showed significant reductions in thrips under strip tillage (Tubbs et al. 2010). On the other hand, populations of plant pests including slugs (Luna and Staben 2003) and plant-parasitic nematodes (Overstreet et al. 2010) have been reported to increase in strip-tillage systems.
Reduced tillage systems can have both positive and negative effects on diseases. Since the survival of many important plant pathogens (e.g., Exserohilum turcicum, northern corn leaf blight) is reduced with incorporation of crop residue, reduced tillage systems may result in greater inoculum levels for successive crops. On the other hand, the presence of crop or cover crop residue on the soil surface can reduce propagule dispersal by minimizing run-off and soil splashing. For example, Ristaino et al. (1997) showed that planting bell pepper into wheat stubble reduced propagule dispersal and incidence of Phytophthora blight. Similarly, rots of pumpkin caused by Plectosporium tabacinum and/or Didymella bryoniae were less in no-tillage plots compared to conventional tillage plots (Everts 2002).
Weeds in strip-tillage systems. The most commonly cited constraint to adoption of reduced tillage systems is weed management. Weeds have been acknowledged as an important impediment to adoption of strip-tillage systems in vegetables (Luna and Staben 2003; Morse 1999; Walters and Kindhart 2002). In strip-tilled pumpkin trials conducted in Long Island, pumpkin yields were reduced, and weed pressure higher in two of three on-farm trials reported (Rangarajan et al. 2006). Since many vegetable growers rely heavily on soil disturbance to uproot and bury weeds, reduced tillage systems often present a weed management challenge for vegetable growers.
In field crops, reduced tillage systems were not widely adopted until low-cost herbicides became available to compensate for lack of tillage. However, in many vegetable crops, herbicide options are limited. This lack of effective herbicides has been cited as an obstacle to adoption of reduced tillage cucurbit production, and likely contributes to limited adoption in other crops as well (Ne-Smith et al. 1994; Walters and Kindhart 2002).
As with insects, the impact of tillage on weeds depends critically on complementary management practices. In particular, strip-tillage in combination with winter cover crops may result in comparable weed suppression relative to conventional tillage without the need for additional herbicides. However, the long term effects of tillage and cover crop practices on weeds are unclear, as are the interactive effects of tillage and cover crops on weeds, insects, diseases and crop health in multiple crops in a vegetable rotation.
The central objectives of our proposed work were 1) to evaluate the interactive effects of strip-tillage, cover crops, and weed management intensity within vegetable cropping systems on soil health, pest population dynamics, and crop quality and yield; and 2) to work with growers and extension educators to disseminate useful information and identify and address constraints to adoption of reduced tillage production systems.