Long Term Research on Agricultural Systems
The Long Term Research on Agricultural Systems (LTRAS) is a hundred-year study located on the main plots at the Russell Ranch Sustainable Agriculture Facility. LTRAS measures the long-term impacts of crop rotation, farming systems and inputs of water and nitrogen on agricultural sustainability. The cropping systems in the long-term experiment include rainfed and irrigated systems, organic and conventional systems, and different forms and quantity of nitrogen inputs.
Original Experimental Design
The cropping systems at Russell Ranch were designed to fall along a gradient of increasing irrigation and fertilization intensity. The 10 systems were originally all two-year rotations and included corn/tomato, wheat/tomato, wheat/fallow and wheat/legume rotations. There are six one-acre plots per system, three for each of the two phases. Each plot also contains 40 micro-plots which allow scientists to test hypotheses on a short-term basis. These micro-plots are outside of the yield measuring area, which is used for long-term data collection.
Current experimental design
The cropping systems at Russell Ranch have changed slightly since 1993, to adapt to new trends and constraints. In 1999, a new transitional system (**) was added which converted conventional plots to organic plots. A side-by-side comparison of long and short-term organic corn-tomato was analyzed by graduate student Elizabeth Martini (see her paper here). From 2003-2007, all one-acre plots of the tomato/corn systems were split in half and reduced tillage treatments were compared to standard tillage treatments (see tillage results here). Additional modifications have been made to the original design in response to increasing budget constraints. The star (*) in the table above indicates that the corn was replaced with wheat from 2010-2012 .
The cropping systems of the long-term project are being evaluated to be more flexible and responsive to current trends, while maintaining the integrity of the long-term experiment. New rotations added in 2012 include a six-year rotation (alfalfa-tomato-corn) as well as perennial native grasses. Additional new projects being discussed include: integrated nutrient management systems, animal forage systems, woody perennials (orchards and vineyards), reduced tillage rotations and restoration ecology.