By Jeff Mitchell, Anil Shrestha and Marsha Campbell-Mathews
University of California Conservation Tillage Workgroup
 
(July 13, 2007) - - From Hanford to Hilmar, there is an unprecedented increase in 2007 in the use of a variety of conservation tillage (CT) production practices for dairy forage production in California’s San Joaquin Valley (SJV). 

No-till twin-row corn planting, Hilmar, CA

Corn planting following strip-tilling, Turlock, CA

Strip-tillage is most effectively accomplished when the soil in the vertical zone that is to be tilled is relatively dry, but not so dry that the strip-till implements brings up large soil clods or bends under the high resistances that can exist in very dry conditions.  Ideally, some moisture is required for successful strip-tilling, but not so much that compacted layers are not shattered or broken up.  Thus, in forage corn production systems, strip-tillage would generally be done immediately following winter small grain chopping and before pre-irrigation for corn.  Attempting to strip-till when the soil is too dry, however, can cause the system to fail because either the seedbed conditions will be too cloddy to plant into  or because the strip-till implement itself may bend or break.
 
Assuring that the corn planter tracks or follows precisely in strip-tilled zones is essential and can be accomplished either by using the same GPS (Global Positioning System) system for both strip-tillage and planting operations, or simply by having the planter hooked up to the strip-tiller and performing both operations together in one pass.  Work by Mike Petersen, now the Precision Tillage Agronomist for Orthman Mfg. and formerly a conservationist with the USDA Natural Resources Conservation Service in Greeley, CO, has shown that corn root growth can be reduced by roughly a third at 55 days after planting with misalignment between strip-tiller and planter of as little as four inches.  Both GPS-enabled strip-tillage and hooking up the strip tiller with a planter in one operation have been successfully done in a number of forage corn fields in the SJV in 2007.

Strip-tilled corn stands, Turlock, CA

While there were slight differences in stands achieved in strip-tilled fields relative to traditional tilled fields, particularly at the Turlock site where strip-tilling was done before preirrigating, and at the first Hanford site where a higher seeding rate was used in the traditional till field, generally adequate stands can be found using strip-till.

The majority of strip-till forage producers use herbicide-tolerant corn varieties.  Because corn forage yield losses occur particularly if weeds are not managed during the first four weeks following corn emergence, timing of herbicide applications must be early enough to prevent weeds from competing with corn seedlings.  This generally means spraying once weeds have emerged following the spring preirrigation at a time closely coinciding with corn planting.  Additional research is needed, however, on long-term early season weed management strategies so as to achieve control without allowing herbicide-tolerant weeds to develop.  A common concern of corn growers is the increase in weed pressure in CT compared to conventional plots.  However at the Turlock and Modesto sites, the strip-till plots had similar or lower number of weeds than the conventional tillage plots. This suggests that with appropriate weed management strategies, such as timing of herbicides, strip-till plots may not result in increased weed densities compared to the conventional plots.

Strip-till plot

Conventional plot

Numerous studies on the use of “starter” or “at seeding” fertilizer applications typically find no advantage in productivity when compared to no starter under traditional tillage management systems.  Under CT, however, the majority of research studies indicate benefits to both on-seed starter and additional nitrogen placed to the side or below the seed.  Reasons for this difference under no-till are likely related to the fact that soil disturbance or mixing is eliminated and there is a greater tendency for nutrient stratification under no-till.  One of the capabilities of strip-till that has been exploited to advantage in areas such as Colorado and Nebraska where strip-tilled grain corn production is common, is applying fertilizers at two different depths with the strip-till pass.  Adoption of optimized fertilization practices for these conservation tillage forage production systems in California is just beginning.
 
In other parts of the country, CT practices such as no-till and strip-till have been associated with improvements in soil structure and water conservation over time.  By disturbing a smaller soil volume, there production techniques provide conditions for worms to flourish and to increase soil porosity, and by preserving residues on the surface, soil evaporation losses may be reduced (Photo 4).  Impacts of sustained CT on soil, water and air resource conservation in California are also only beginning to be documented and understood.

Strip-tilled corn stand, Modesto

For more information about strip-till, no-till and ‘CT-enabled triple-cropping,” contact CT Workgroup Chair, Jeff Mitchell, at (559) 303-9689 or This e-mail address is being protected from spambots. You need JavaScript enabled to view it .