The trend among northern Plains farmers is toward using less tillage to produce field crops with more residue left on the soil surface and strip-till is one system being utilized in the area. Researchers from South Dakota State University detail some of the benefits and considerations for implementing and managing strip-till.
Advantages of strip-till include, reduced soil erosion because most of the soil remains covered with crop residue throughout the year, increased water infiltration compared with full-field tillage, less carbon released into the atmosphere and higher levels of soil organic matter and crop yields that are similar or higher compared to other tillage systems.
Other benefits include, better seed germination and plant emergence because the tilled strips warm sooner in the spring, soil moisture conservation because most of the soil surface area is covered with crop residue and reduced expenses, including fuel and labor, by eliminating some primary and secondary tillage.
Strip-Till Improves Carbon Sequestration
Soil organic matter plays a critical role in the global carbon cycle. Soil can act as both a major source for carbon released into the atmosphere and a sink to store carbon. When carbon is stored in the soil, it is not released to the atmosphere as greenhouse gases, particularly carbon dioxide (CO2) and methane (CH4). Tillage increases microbial action on organic matter stored in the soil and normally increases the rate of decomposition that changes organic carbon into CO2. Soil organic matter is directly related to soil fertility and positively correlated with agricultural productivity potential.
Besides reducing greenhouse gases, other advantages of increasing or maintaining a high level of soil organic matter include reduced soil erosion, increased resistance to compaction, increased biological activity and enhanced soil fertility. Since tillage results in soil carbon loss, identifying tillage methods that reduce the amount of carbon released into the atmosphere is important.
A comparison study of soil CO2 emissions following fall moldboard plowing, disk ripping and strip tilling conducted in 2005 in Minnesota (Faaborg et al., 2005) determined that strip tillage maintained more soil carbon than moldboard plowing and disk ripping. Disk ripping and strip tillage released 53.2 and 82.6 percent less CO2, respectively, than moldboard plowing (Figure 1). Moldboard plowing disturbed and exposed the greatest amount of soil, allowing carbon previously stored as organic matter or present as CO2 in the soil atmosphere to escape into the atmosphere.
Crop Production With Strip Till
Strip-till systems move crop residue from the soil surface over the seedbed, resulting in soil temperatures similar to conventional tillage systems. No-till systems leave residue on the soil surface over the seedbed, resulting in lower soil temperatures compared with tilled soil. University of Minnesota research in southern Minnesota (Stahl, DeJong-Hughes) shows an aggressive strip-till machine can clear away sufficient residue to promote soil warming similar to moldboard plowing in a continuous corn rotation.
In a corn-soybean rotation, soil temperatures were similar for strip till and chisel plow and lower for no till. Similarly, research in the Red River Valley (Prosper, N.D., and Moorhead, Minn.) in 2007 indicated comparable temperatures between conventional tillage and strip till (Overstreet et al., 2007). The soil temperature advantage with strip till compared with no till promotes faster plant emergence and development. This advantage is enhanced when soil temperatures are lower and approach the lower threshold for crop seed germination.
For example, early planted strip-till corn or soybeans likely will emerge sooner than in a no-till system. Earlier plant establishment normally increases crop yield and quality. Earlier emergence and stand establishment also promotes earlier crop canopy closure, reducing mid- and late-season weed seed germination, and providing a better chance for young plants to establish and withstand disease and insect pressure.
Conserves Soil Moisture
Strip tillage on the northern Great Plains in the United States conserves soil moisture by trapping winter snow and reducing evaporation and transpiration losses, resulting in more soil moisture available for plants, particularly later in the growing season during the plant reproductive stages.
When To Strip Till
In the northern Great Plains, strip tillage with fertilizer application usually is performed in the fall after harvest, followed by planting in the spring. Fall tillage allows time for the soil in the berm to smooth during the winter and warm in the spring before crop planting. Strip tillage operations can be performed in the spring, particularly in regions with coarse-textured and lower organic matter content soils. Research conducted in 2007 on loam soil at Carrington, N.D., indicates similar crop yield between fall and spring strip-tillage.
Research indicates strip-tillage works well with crops grown with 30-inch row spacing; however, narrower row spacings also work, but residue management is more difficult with less space for residue. Mounting strip-till units on staggered bars allows residue to flow between strip-till units in narrower row spacing. Strip tillage is used with row crops, such as corn, sugar beets, soybeans, dry beans and sunflowers.
North Dakota and Minnesota research shows corn yields are similar or higher when strip till is used compared with other tillage methods. The University of Minnesota Extension compared four tillage systems for corn following soybeans on farm fields in 2004 and 2005 (DeJong-Hughes and Vetsch, 2007). The average daily temperatures were below normal in 2004, resulting in higher corn yields with strip till compared with no till and conventional till. The 2005 growing season was warmer than average, resulting in all tillage methods producing excellent corn yields while maintaining adequate residue cover to protect the soil from erosion.
Another ongoing study started in 2007 in southern Minnesota with a continuous corn rotation shows corn yields grown in strip-tilled soil were similar or higher than with other tillage systems in all situations except when soil conditions are too wet to properly operate strip-till machines in the fall. This research uses moldboard plowing, disk ripping and strip till on a continuous corn field to study the effects of residue placement on seedling emergence, soil temperature and grain yield. The soils at the site ranged from loam to heavy clay loam, with poor internal drainage and no tile drainage.
Four years of North Dakota corn research conducted at Carrington and Fargo in 2007-10 (Endres, Franzen and Overstreet) on fall strip till shows yields were 6 bushels per acre greater than with conventional till. At Carrington, corn was grown in 30-inch rows on a loam soil, and at the Red River Valley sites in 22-inch rows.
Dry Edible Beans
Dry edible bean production using strip till significantly reduces soil erosion potential compared with conventional tillage. Moisture conservation is an additional benefit in arid areas. The obvious disadvantage with strip-till beans is changing harvest strategies. Strip-till edible beans require direct harvest, which potentially increases harvest loss. However, reduced harvesting equipment, time and labor, and potentially improved seed quality may offset increased harvest losses.
Preliminary data in 2007 and 2009-10 by NDSU researchers at Carrington with fall strip-till pinto beans indicate potential for similar seed yield compared with conventionally tilled bean, and greater than with no till.
Production advantages may be gained with strip till for soybeans in arid areas because of moisture conservation, or if the crop is planted early because of warmer soils compared with no till. NDSU research during 2005-10 indicated soybean yields of 2 bushels more per acre with strip till compared with conventional till or no till (Endres, Franzen and Overstreet).
The University of Minnesota Extension conducted research in southern Minnesota comparing soybean yields in a rotation following strip-tilled corn in chisel-plowed, no-till and strip-till fields (DeJong-Hughes, Stahl). The yields in 2006 and 2008 were similar, reflecting soybean versatility in various tillage systems. In 2007, the no-till fields yielded less than the chisel-plowed and strip-tilled fields.
NDSU strip-till research with sugar beets grown in 22-inch rows was conducted during 2005-07 at several Red River Valley locations (Franzen and Overstreet, 2007). Sugar beet yields were similar among tillage systems in two of the three years. Strip-till yields were approximately the same as conventionally tilled plots.
Sunflower production using strip till is limited in the northern regions of the United States. Strip-till research trials and commercial production in Kansas show some success for sunflowers (Olson et al., 2005). Four years of NDSU strip-till research at Carrington during 2006-09 by Endres have indicated similar sunflower performance for seed yield and quality among tillage systems, including strip till.
General Fertilizer Considerations
Phosphorus and potassium can be band-applied during strip-till operations. Banding phosphorus and potassium allows for a rate reduction of one-third compared with broadcast application on a medium or low-testing soil (University of Minnesota Fertilizer Recommendations, 2001). Phosphorus and potassium also can be applied to crops as starter fertilizer with the planter.
Nitrogen also can be applied using strip-till equipment. However, fall nitrogen application is not recommended in sandier, lighter soils.
Nitrogen can be applied as a starter fertilizer and side dressed later in the growing season. Carrington, N.D., research conducted in 2010 (Endres, Hendrickson, Glatt) show similar plant emergence and stands among tillage systems and fertilizer placement methods. However, among strip-till treatments, in-furrow fertilizer had lower plant densities compared with other methods of applying fertilizer. Grain yield and quality were similar among treatments. However, among strip-till treatments, seed yield was higher with fall deep-band followed by spring in-furrow fertilizer compared with other fertilizer treatments.
The Oakes Irrigation Research Site conducts research on growing continuous corn and corn following soybeans in a strip-till system to determine efficient nitrogen fertilizer rates. Results from these studies can be used to evaluate likely corn yield and quality for various fertilizer rates (W. Albus, L. Besemann and H. Eslinger. 2010). More information is available online at www.ag.ndsu.nodak.edu/oakes/oakes.htm.
Management Tips for Strip-Till
- Match the strip-till row width with the planter row width.
- Leave corn stubble standing for maximum air movement and less matting of residue. Build strips between the previous crop rows.
- For the greatest soil warm-up and seed-to-soil contact, strip tillage should be performed in the fall.
- In cooler, fine-textured soils, strip-till equipment should clear the berm to less than 10% residue for faster soil warming in the spring.
- In high-moisture conditions, build berms approximately 3 inches high in the fall so they are at least 1 inch high by planting. In arid conditions, berms can be depressed to collect winter snow.
- The economic advantages of strip-till are improved if banding phosphorus and potassium fertilizer with the fall strip operation.
- Avoid slopes of more than 7% without contouring; otherwise, risk of soil erosion can occur in tilled strips.