Research

Conservation agriculture

Managing soil health for sustainable agriculture
Book chapter
2018

Long-term use of cover crops and no-till shift soil microbial community life strategies in agricultural soil
PLOSone 
February 2018

Conservation agriculture systems
CAB Reviews
May 2019

The article highlights a series of examples of conservation agriculture systems being applied around the world and concludes by issuing a call to action aimed at developing and more widely adopting food production systems that look long-term, mimic natural systems and transcend jargon.

Transition to conservation tillage evaluated in San Joaquin Valley cotton and tomato rotations
California Agriculture journal
April/June 2008

In the San Joaquin Valley, cotton and tomato production systems rely on considerable intercrop tillage to prepare the soil for seeding.  Tillage clears the soil surface of residues, permits greater soil warming in the spring and clean harvest conditions in the fall, and provides weed control

Overhead and Drip Irrigation System Effects on Tomato Growth and Yield in California's Central Valley
HortTechnology
December 2014
Despite the worldwide importance of overhead, mechanized irrigation for crop production, the potential of this technology has been poorly studied in California. Field studies were conducted at Five Points, CA, in 2010 and 2012 to compare the effects of overhead irrigation (OH) and drip irrigation (DR) on transplanted tomato (Solanum lycopersicum) crop growth and yield.

Trade-offs between winter cover crop production and soil water depletion in the San Joaquin Valley, California
Journal of Soil and Water Conservation
November/December 2015
Cover crops are currently not widely used in annual crop production systems in California’s semiarid Central Valley due to concerns about lost opportunity costs and uncertainties about water use. From 1999 through 2014, we quantified cover crop biomass production for a variety of mixtures under winter precipitation and limited supplemental irrigation. In a separate study, we also determined changes in soil water storage under three cover crop mixtures compared to fallowed plots during two (2013 and 2014) winter periods to investigate tradeoffs associated with water use by cover crops in this region.

Tillage and Cover Cropping Affect Crop Yields and Soil Carbon in the San Joaquin Valley, California
Agronomy Journal
February 2015
Rising costs and air quality regulations have created interest in California’s San Joaquin Valley (SJV) in production systems that reduce tillage operations and soil disturbance. From 1999 to 2009, we evaluated conventional (CT) and reduced tillage (RT) systems for a cotton (Gossypium hirsutum L.)/tomato (Solanum lycopersicon Mill.) rotation with (CC) and without (NO) cover crops in a Panoche clay loam soil (fine-loamy, mixed, superactive, thermic Typic Haplocambid) in Five Points, CA, in terms of yield, soil C, and the NRCS soil conditioning index (SCI).

Subsurface Drip and Overhead Irrigation Effects on Conservation-tilled Cotton in the San Joaquin Valley
Journal of Crop Improvement
May 2014
Conservation cropping systems are being developed for cotton (Gossypium spp.) traditionally grown on raised beds with several soil-disturbing tillage passes in the San Joaquin Valley (SJV) of California, USA. Overhead (OH) irrigation and subsurface drip irrigation (SSDI) systems are water-conserving techniques being tested with reduced tillage in the SJV. However, crop growth, yield, microclimate, and pest population dynamics in these systems have not been documented.

Onion Growth, Yield, and Production Costs as Affected by Irrigation System
Journal of Crop Improvement
October 2014
Onion (Allium cepa) production in California's San Joaquin Valley (SJV) typically involves intensive tillage and sprinklers for crop establishment followed by drip irrigation (DR). Studies were conducted at Five Points, California, in 2011 and 2013 to compare minimum tillage (MT) practices under overhead irrigation (OH) and DR relative to crop growth, yield, and costs. The experimental design was a randomized complete block with four replications of each irrigation treatment. Crop growth in both systems was similar; however, there was a year X irrigation system interaction for crop yields.

Evolution of Conservation Tillage Systems for Processing Tomato In California's Central Valley
HortTechnology
October 2012
Traditional processing tomato (Solanum lycopersicum) production in California’s Central Valley relies heavily on tillage to produce high yields. However, recent research and farm innovation have produced a variety of conservation tillage (CT) management alternatives that cut costs, reduce soil disturbance, and produce fewer emissions. A 12-year study in Five Points, CA, demonstrated that CT methods reduced tractor passes by 40%, lowered tillage costs by $80 per acre in 2011 dollars, and achieved comparable yields as standard tillage (ST) methods. As comparable yield performance and net profitability are further demonstrated, an array of CT systems will become increasingly attractive to producers and more common in Central Valley tomato growing areas.

Cotton Response to Long-Term No-Tillage and Cover Cropping the San Joaquin Valley
The Journal of Cotton Science
2015
Despite approximately 45% of U.S. cotton being produced using no-tillage (NT) or strip-tillage, these seeding techniques are not yet being used commercially in California.

History of Tillage in California's Central Valley
Soil & Tillage Research
October 2015
The Central Valley (CV) of California is a remarkably productive agricultural region. Much of the productive capacity of the CV stems from the reliable tillage management systems that were developed beginning in the 1930s and that changed very little until the 1990s and even more dramatically in the 2000s.

Conservation tillage systems for cotton advance in the San Joaquin Valley
California Agriculture Journal
July-September 2012
During a three-year comparison study from 2001 to 2003, cotton yields in strip tillage plots matched or exceeded yields of standard tillage plots in all three years. In a 12-year study from 1999 to 2011, tillage costs were lowered an average of $70 per acre in 2011 dollars using no-tillage compared to standard tillage while achieving statistically comparable yields.

No-tillage and high-residue practices reduce soil water evaporation
California Agriculture journal
April-June 2012
Reducing tillage and maintaining crop residues on the soil surface could improve the water use efficiency of California crop production. In two field studies comparing no-tillage with standard tillage operations (following wheat silage harvest and before corn seeding), we estimated that 0.89 and 0.97 inches more water was retained in the no-tillage soil than in the tilled soil. In three field studies on residue coverage, we recorded that about 0.56, 0.58 and 0.42 inches more water was retained in residue-covered soil than in bare soil following 6 to 7 days of overhead sprinkler irrigation.

2010 Tillage Practices Survey Findings
January 2012
California’s Conservation Agriculture Systems Institute (CASI) has prepared its survey of tillage management acreage for 2010. This tillage survey was conducted as an ongoing comparison of annual row crop acreage that is farmed under different tillage systems throughout the Central Valley region of California. Over 35 local NRCS, University of California and private sector experts were surveyed and results were compared with 2010 County Agricultural Commissioner cropland acreage. Previous surveys have been conducted in 2004, 2006, and 2008.

Conservation Tillage Systems for California Cotton: A Review of Recent Research Findings
January 2011
In a this pre-print research report, the authors provide a summary of findings resulting from two long-term studies that have evaluated a variety of sustained CT production systems for cotton in California’s San Joaquin Valley. The report gives producers who may be interested in growing cotton using CT with information on the performance and initial challenges of these systems.

Classification of Conservation Tillage Practices in California Irrigated Row Crop Systems
February 2009
Some of the tillage systems that were recently introduced in California resemble well-known forms of conservation tillage, such as no-tillage and strip-tillage. However, many of the new systems are quite different from these better-known forms.

Conservation Tillage Tomato Production in California's San Joaquin Valley
January 2009
In California's Central Valley, CT approaches are receiving interest as a means to cut costs and reduce dust and diesel fuel emissions from production fields. This publication summarizes recent advances in the development of CT tomato production and describes what CT tomato systems might look like.

Strip Tillage in California's Central Valley
January 2009
Strip-tillage is a form of conservation tillage that clears crop residues in a narrow zone of soil and loosens subsoil layers prior to planting. Strip-tillage decreases both the volume of soil that is disturbed and the amount of dust that is typically generated in intercrop tillage, and it also reduces fuel, labor, and equipment costs when compared with traditional broadcast tillage.

Tillage Effects on Spatiotemporal Variability of Particulate Organic Matter
Applied and Environmental Soil Science
2009
This study was performed to evaluate effects of no-till (NT) and standard tillage (ST) on POM in two 15-ha neighboring fields from 2003 to 2004.

Annual carbon and nitrogen loadings for a furrow-irrigated field
Agricultural Water Management
2009
As part of a larger carbon sequestration project that focused on potential of carbon sequestration for standard and minimum tillage systems of irrigated crops, the effects of furrow irrigation on the field carbon and nitrogen loading were evaluated.

Earthworm populations in relation to soil organic matter dynamics and management in California tomato cropping systems
Applied Soil Ecology
2009
This study sought to explore linkages between agricultural management, earthworms and aggregate associated SOM dynamics through a survey of tomato (Solanum lycopersicum L.) cropping systems in northern California.

Soil nitrous oxide emissions in long-term cover crops-based rotations under subtropical climate
Soil and Tillage Research
2009
This study aimed to evaluate the effect of long-term (19 and 21 years) no-till maize crop rotations including grass [black oat (Avena strigosa Schreb)] and legumecover crops [vetch (Vigna sativa L.), cowpea (Vigna unguiculata L.Walp), pigeon pea (Cajanus cajan L. Millsp.) and lablab (Dolichos lablab)] on annual soil N2O emissions in a subtropical Acrisol in Southern Brazil.

Transitioning from standard to minimum tillage: Trade-offs between soil organic matter stabilization, nitrous oxide emissions, and N availability in irrigated cropping systems
Soil and Tillage Research
2009
This study compares the influence of minimum versus standard tillage on changes in soil nitrogen stabilization, nitrous oxide emissions, short-term
nitrogen cycling, and crop nitrogen use efficiency 1 year after tillage conversion in conventional, low-input, and organic irrigated, maize–tomato systems in California.

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