Conservation Tillage Reduces Cost, Organic Matter Loss...and Emissions

While the following story pertains to agriculture, the same concepts can be applied to urban management of soil...less surface disturbance means less dust and more stable growing environment.



Conservation tillage allows growers to reduce the number of times that tractors are run through their fields, for savings in time, energy and labor. The authors studied how the practice, with and without cover crops, affects yields, dust production and other factors in a cotton-tomato rotation.

Many tillage practices, however, can be a significant production cost, a cause of soil organic matter losses and a source of particulate matter emissions.

On average, 9 to 11 separate tillage related operations, each involving heavy equipment, are conducted during the fall through spring to prepare the soil for summer cropping in most current San Joaquin Valley cotton and tomato production fields. Deep tillage often is used in these systems to alleviate compaction that results from frequent tillage passes and harvest operations.

These operations account for up to 20% of production costs (Carter 1996), and require high energy and increased subsequent effort to prepare seed beds.

The adoption of conservation tillage (CT), or reduced tillage practices, may be a viable means for improving field-crop production systems if their profitability and capacity to conserve natural resources can be demonstrated.

In their many and varied forms, conservation tillage systems aim at reducing primary, intercrop tillage operations such as plowing, disking, ripping and mulching. As a result of these deliberate reductions in tillage, surface residues may accumulate and must be managed, and new techniques for crop establishment must be developed. Despite the potential attractiveness and utility of reduced-tillage production alternatives, conservation tillage adoption rates in agronomic row crops are very low in California, less than 2% (CTIC 2004).

Reasons for California’s low adoption rate include a lack of locally available conservation tillage equipment, inexperience with conservation tillage techniques, the predominance of surface, or gravity, irrigation systems and the fact that the tillage-intensive systems used in the San Joaquin Valley for several decades are generally quite productive (Mitchell et al. 2007).

RESULTS OF THE RESEARCH

The researchers compared standard tillage (ST) and conservation tillage (CT) for tomato and cotton production systems, with winter cover crops (CC) and without (NO), in Five Points, Calif., from 1999 to 2003.

Conservation tillage reduced tractor trips across the field by 50% for tomatoes and 40% for cotton compared to standard tillage.

When averaged over the 2001 to 2003 period (when the conservation tillage systems were established), tomato yields in CTNO were 6 to 8 tons per acre higher than the other treatments.

In cotton, the STNO cotton yields during this period were the highest of all treatments and were 276 pounds per acre higher than the CTNO system.

In-field dust concentrations were also significantly reduced by conservation tillage.

Our results suggest that conservation tillage may be a viable alternative for managing tomato and cotton crops in the San Joaquin Valley, but that fine-tuning of the systems is needed.

by Jeffrey P. Mitchell, Randal J. Southard, Nicholaus M. Madden, Karen M. Klonsky, Juliet B. Baker, Richard L. DeMoura, William R. Horwath, Daniel S. Munk, Jonathan F. Wroble, Kurt J. Hembree, and Wesley W. Wallender

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