State Water Resources Research Institute Program

Project ID: 2011CA274B
Title: Optimizing efficiencies and economics of solid-set subsurface drip and overhead mechanized systems with flat-planted cropping systems
Project Type: Research
Start Date: 3/01/2011
End Date: 2/29/2012
Congressional District: 44
Focus Categories: Irrigation
Keywords: irrigation
Principal Investigator: Mitchell, Jeff
Federal Funds: $ 0
Non-Federal Matching Funds: $ 33,777
Abstract: Improved practices and better information have led to widespread adoption of more efficient irrigation technologies in California during the past several decades. Subsurface drip irrigation, for example, has been shown to increase productivity and profitability, reduce subsurface drainage, and improve weed control. A recent survey of UC Cooperative Extension Advisors and San Joaquin Valley (SJV) West Side farmers indicated that over 85% of processing tomato acreage in the Central SJV is now produced using permanent bed subsurface drip irrigation. When subsurface drip is used, however, as it is commonly used with SJV tomatoes, farmers tend to be limited to tomatoes followed by tomatoes due to the placement, spacing and configuration of the buried tape. Rotating to other crops becomes more difficult and costly, and as a result, continuous monocultures often result with corresponding risks for pathogen build-up in the soil.

Similar surveys of irrigation technology adoption from the High Plains Aquifer of the Midwestern United States, the largest freshwater aquifer in the world, over the past fifteen years indicate a steep decline of more than 50% in the use of surface (flood or furrow) irrigation and a corresponding increase in the use of overhead mechanized irrigation systems that employ low-pressure, "dropped" nozzle packages that suspend sprinkler heads just above the canopy of the crop, increasing application efficiency by decreasing the amount of water lost to evaporation and drift, particularly in hot and windy areas. It is currently estimated that in several other regions of the US and the world, overhead center pivot systems are the dominant irrigation method. Somewhat conservative estimates indicate that there are between 175,000 - 200,000 center pivot and linear move overhead systems currently in use in the US covering 22,000,000 to 26,000,000 acres of automated irrigation, or approximately 40% of all irrigated acres in the country. These numbers are rapidly changing in many areas as flood or surface irrigation is being converted to overhead. Similar trends in increased adoption of overhead mechanized irrigation have been documented worldwide.

Overhead irrigation is currently estimated to be used on less than 1% of California's crop acreage. Very recently, however, within the past five years, there has been a dramatic increase in the number of overhead irrigation systems that have been introduced into the Central SJV. Overhead mechanized irrigations systems have been generally shown to have higher application uniformities and efficiencies than surface systems. Higher application efficiencies can lead to reduced water requirements. In irrigated areas such as the Ogallala Aquifer or the south-central region of Brazil, where overhead irrigation has rapidly expanded, its use is often coupled with various sorts of conservation tillage (CT) practices because furrows that permit surface water movement and that require considerable intercrop tillage, are no longer required. Direct-seeding or no-till planting is thus enabled in overhead systems. After sustained CT production, soils may store more water than conventionally tilled soils due to the maintenance of macropores. In addition, soils with stubble cover also reduce wind velocities and temperatures at the surface, which may reduce evaporation from the soil. Coupling no-till and surface residue preservation with overhead, low-pressure irrigation may thus be a means for conserving water and improving the production efficiencies in SJV cropping systems, and also for providing greater cropping flexibility to rotations, however both the production mechanics and related research base are currently lacking that might substantiate this claim.

Conservation tillage provides significant means for reducing costs, dust emissions, and fuel use in many crop production systems. We recently demonstrated that costs can be reduced by 14 - 18% when using CT cotton planting and postharvest stalk management systems, while yields were maintained. No-till and strip-till crops are successfully produced in the South, the Midwest and in Brazil. No-till, flat-planted late-season cotton has been produced profitably for several years in AZ. No-till and strip-till forage production has been successful in some SJV dairies. These experiences indicate that no-till production is feasible and could ultimately become a viable option for the SJV if focused and intensified research is dedicated to it.

In order to effectively "couple" highly efficient irrigation systems such as drip and overhead with the use of cost-cutting CT practices, however, new production paradigms are needed to optimize the performance of the merged technologies. Traditional raised planting beds, - we propose, - will no longer be required and indeed, would present unneeded complications and expense to producers. In diverse crop rotations, for example, that include traditionally bedded crops such as tomatoes and cotton as well as broadcast-seeded field crops such as wheat or triticale, having beds may be desirable for the row crops in such a rotation under surface or furrow irrigation, but raised beds under sustained CT cropping may become a problem due to residues accumulating in furrows and causing seeding difficulties for drill-seeded crops.

To overcome such problems and to develop what may become truly "next generation" precision irrigation and conservation tillage systems, we propose to evaluate overhead mechanized and solid-set subsurface drip irrigation systems with flat-planted cropping systems as a means to optimize irrigation and cropping efficiencies and to also increase the overall precision and flexibility of crop sequences. This cropping, irrigation, and tillage systems integration recognizes that it may be via the coupling or merging of these technologies that a higher level of production efficiencies will be achieved and it anticipates what very well may be the eventual inevitability of such precision farming systems in the SJV.The work proposed here will therefore develop information on the relative performance of overhead and solid-set drip irrigation under minimum and no-tillage management on productivity, profitability, water use efficiency, salinity, and vertebrate pest pressure in a large-scale, replicated study to be conducted at the University of California West Side Research Center in Five Points, CA. This proposed work will be very visibly disseminated throughout the SJV via our very successful CT Workgroup's extension education programs and will provide training to a UC Davis hydrology student.

Progress/Completion Report, 2011, PDF

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