Research archive

Tillage and seasonal emissions of CO2, N2O and NO across a seed bed and at the field scale in a Mediterranean climate
Agriculture, Ecosystems and Environment
2009
We quantified CO2, N2O, and NO emissions from an irrigated field under standard tillage and in a field recently converted to minimum tillage in Yolo County, Calif., under a Mediterranean climate.

Modeling shows that alternative soil management can decrease greenhouse gases
California Agriculture journal
2009
Based on data from field studies and an ecosystem computer model, we assessed impacts on yields and the total potential for reducing  greenhouse-gas emissions of certain alternative practices in California.

Building Up Organic Matter in a Subtropical Paleudult under Legume Cover-Crop-Based Rotations
Soil Science Society of America Journal
September-October 2009
The potential of conservation management systems to ameliorate degraded agricultural soils and mitigate global warming is related to their potential for long-term stabilization of soil organic matter. This study was performed in a 19-year-old experiment that was set up on a degraded Paleudult in southern Brazil to evaluate the effect of seven no-till crop rotations and mineral N fertilization on soil organic C stocks (0–17.5-cm depth) and estimate
rates of soil organic matter dynamics in these systems under subtropical climate conditions.

2008 Acreage Survey
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.

Conservation Tillage and Weed Management
Tillage has been a major agricultural weed control technique for several decades, so the development of CT systems that advocate no-tillage or reduced tillage has significant implications for growers.

Tillage and Crop Management Effects on Air, Water and Soil Quality in California
September 2008
In California, an adaptable model of CT has emerged across a broad range of crop production systems that minimizes or eliminates primary tillage operations of disking, plowing, ripping, and chiseling, and that manages residues in ways to enable efficient and successful planting, pest management, and harvesting. While these production alternatives are relatively new to California, there is a growing body of information related to their likely impacts on air, water, and soil quality and on resource conservation.

Transition to conservation tillage evaluated in San Joaquin Valley cotton and tomato rotations
California Agriculture journal
April 2008
The study compared standard tillage and conservation tillage for tomato and cotton production systems, with winter cover crops and without, in Five Points, Calif., from 1999 to 2003. Conservation tillage reduced tractor trips across the field by 50 percent for tomatoes and 40 percent for cotton compared to standard tillage.

Aggregation and C and N contents of soil organic matter fractions in a permanent raised-bed planting system in the Highlands of Central Mexico
Plant Soil
2008
Permanent raised bed planting with crop residue retention is a form of conservation agriculture that has been proposed as an alternative to conventional tillage for wheat production systems in the Central Highlands of Mexico. A field experiment comparing permanent and tilled raised beds with
different residue management under rainfed conditions was started at El Batán (State of Mexico, Mexico) in 1999. The percentage of small and large macroaggregates and mean weight diameter (MWD) was significantly larger in permanent raised beds compared to conventionally tilled raised beds both with full crop residue retention (average for maize and wheat), while the percentages free microaggregates was lower.

The relationship between landform and the distribution of soil C, N and P under conventional and minimum tillage
Geoderma
2008
The objective of this study was to examine the interactive effects of tillage and land forms (erodibility) on the redistribution of C, N and P within an agricultural landscape. Soils were sampled from an undulating maize field in central Belgium.

Short-Term Fates of Carbon-13-Depleted Cowpea Shoots in No-Till and Standard Tillage Soils
Soil Science Society of America Journal
November-December 2007
The fate of carbon from 13C-depleted cowpea shoots was examined to assess factors affecting residue carbon dynamics in soil cores taken from plots under no-till vs. standard tillage.

Soil Food Webs and Carbon Dynamics in Response to Conservation Tillage in California
Social Science Society of America Journal
May-June 2007
Reducing disturbance by tillage and addition of crop residues affects soil biota and their role in soil carbon storage. For 1 year in a field station trial in Davis, CA, these treatments were compared: no-tillage + continuous cropping, no-tillage + fallow, standard tillage + continuous cropping, and standard tillage + fallow.

Adoption of conservation tillage in California: current status and future perspectives
Australian Journal of Experimental Agriculture
2007
While there have been several similarities between the development of cropping systems in Australia and California (including climate, the need for irrigation and very diverse, highly specialised crop rotations), the historical patterns of conservation tillage development in the two regions have been quite different.

Influence of earthworm activity on aggregate-associated carbon and nitrogen dynamics differs with agroecosystem management
Soil Biology and Biochemistry
2007
Earthworms are known to be important regulators of soil structure and soil organic matter dynamics, however, quantifying their influence on carbon and nitrogen stabilization in agroecosystems remains a pertinent task. We manipulated population densities of the earthworm Aporrectodea rosea in three maize-tomato cropping systems [conventional (i.e., mineral fertilizer), organic (i.e., composted manure and legume cover crop), and an intermediate low-input system (i.e., alternating years of legume cover crop and mineral fertilizer)] to examine their influence on C and N incorporation into soil aggregates.

Soil aggregates control N cycling efficiency in long-term conventional and alternative cropping systems
2007
Nutrient Cycling in Agroecosystems
This paper presents novel data illustrating how soil aggregates control nitrogen (N) dynamics within conventional and alternative Mediterranean cropping systems.

Long-term impact of reduced tillage and residue management on soil carbon stabilization: Implications for conservation agriculture on contrasting soils
2007
Soil & Tillage Research
Residue retention and reduced tillage are both conservation agricultural management options that may enhance soil organic carbon stabilization in tropical soils. Therefore, we evaluated the effects of long-term tillage and residue management on SOC dynamics in a Chromic Luvisol (red clay soil) and Areni-Gleyic Luvisol (sandy soil) in Zimbabwe.

Considerations of a field-scale soil carbon budget for furrow irrigation
Agriculture Ecosystems & Environment
2006
There is a general lack of information on the effects of irrigation on soil carbon  sequestration in (semi)arid regions. For that purpose we present results of the sediment and C budget of a 30 ha furrow-irrigated corn field in the Central Valley in California.

Linking soil properties and nematode community composition: effects of soil management on soil food webs
Nematology
June 2006
During one year (December 2003-December 2004), we studied the influence of continuous cropping, intermittent fallow, standard tillage and no tillage on the nematode assemblage and the soil food web in a legume-vegetable rotation system in California.

Conservation tillage and cover cropping influence soil properties in San Joaquin Valley cotton-tomato crop
California Agriculture journal
September 2006
Following four years of a cotton-tomato rotation on the west side of the San Joaquin Valley, conservation tillage and cover crops altered physical and chemical properties of soil. In conservation tillage systems, bulk density decreased and available concentrations of nitrate and phosphorus increased. In contrast, the conservation tillage system redistributed potassium to the surface of the soil, lost organic matter and increased salt concentrations, all potentially detrimental to plant growth.

Minimum tillage in vegetable crop production systems in California
ANR Catalog
2004
In an effort to control costs and optimize soil management, a wide range of reduced-tillage or minimum-tillage production systems for vegetables have recently been developed. This publication reviews the major attributes of minimum tillage and current examples of its use in vegetable cropping systems in the San Joaquin Valley and the Salinas Valley of California.

On-farm assessment of organic matter and tillage management on vegetable yield, soil, weeds, pests, and economics in California
Agriculture Ecosystems & Environment
2004
In intensive vegetable production, low organic matter inputs and leaching of nitrate decrease soil quality with time. Four management regimes were compared for their effects on soils and on production issues in a cooperative research project with a commercial vegetable grower in the Salinas Valley, Calif.

On-farm assessment of organic matter and tillage management on vegetable yield, soil, weeds, pests, and economics in California
Geoderma
2003
Here we describe our recent work on responses of soil carbon and nitrogen
dynamics, microbial biomass, and microbial community structure to a tillage event in intensively managed vegetable crop systems in California.

Rototillage, Disking, and Subsequent Irrigation: Effects on Soil Nitrogen Dynamics, Microbial Biomass, and Carbon Dioxide Efflux
Journal of Environmental Quality
2002
This study shows that different tillage implements affect CO2 efflux, nitrate accumulation, and microbial activity, and thus have different effects on soil and atmospheric environmental quality.

Minimum tillage practices affect disease
California Agriculture journal
2002
We studied soil properties of different tillage practices and compared deep minimum tillage (chiseling and ripping) with shallow minimum tillage for lettuce on a farm in the Salinas Valley.

Short-Term Dynamics of Nitrogen, Microbial Activity, and Phospholipid Fatty Acids after Tillage
Soil Science Society of America Journal
2001
We examined the effects of rototillage on microbial biomass C (MBC) and N (MBN), respiration (i.e., soil CO2 production in 1-h incubations), CO2 efflux from the soil surface, inorganic N, nitrification potential, denitrification rate, and phospholipid fatty acids.

Microbial responses to simulated tillage in cultivated and uncultivated soils
Soil Biology and Biochemistry
2000
We investigated the immediate effects of simulated tillage on microbial community structure as determined by phospholipid fatty acid (PLFA) profiles, microbial activity, and carbon (C) and nitrogen (N) pools.