Reducing Air Pollution: Conservation Tillage in Arizona Cotton

Protect and Enhance the Nation's Natural Resource Base and Environment
Research Year: 

Cotton growers typically prepare and maintain fields by performing tillage (soil disturbing) operations that include landplaning; leveling; several disking operations; chisel plowing; and cultivation for weed control and maintenance of irrigation furrows. Historically cotton growers had to follow Arizona statutes related to pink bollworm (Pectinophora gossipiella, Sanders) control which required tillage following cotton harvest. Recent regulatory changes have allowed for a reduction in tillage when a small grain crop is planted following cotton and irrigated in December. Researchers at the University of Arizona are looking at ways to reduce the number of times a farmer has to pass through his fields with a tractor and tillage implement, thereby saving money on fuel and labor without reducing economic returns to growers.

Description of Action: 

Conservation tillage is defined as a production system that eliminates or reduces tillage operations to the minimum required to produce a crop, and in which 30 percent of the previous crop residue remains on the surface after planting. Advantages in other parts of the country have included an increase in the overall productivity of the soil by increasing the soil’s organic material and moisture-holding capacity, and reducing erosion. The Arizona research is looking at whether these advantages will hold true in desert soils. While it has been adopted in other parts of the United States, conservation tillage didn’t catch on with Arizona growers until recently when the cost of diesel fuel increased.

Field experiments were conducted at two CALS agricultural centers (3 years at Marana and 2 years at Maricopa with the third year underway) and also with commercial farmers in central Arizona. These trials compared conventionally tilled cotton and reduced tillage double cropping of cotton and small grains where oats or barley were planted without tillage, following cotton harvest and shredding of the cotton stalks. About 236,000 acres of cotton were grown in Arizona during the last season.


Reduced tillage operations cut back on the amount of dust raised as tractors pass over the field. The conventional cotton tillage regime includes five operations at the end of the season: shred, disk, rip, disk again, and list. In a conservation tillage system there is only the shredding operation at the end of the cotton season. Where a no-till grain drill was used to plant wheat, barley or oats on existing cotton beds (as a cotton to small grain transition), PM-10 dust emissions from tillage operations were reduced about 80 percent in the fall (November/December). During the transition from the cotton harvest to the planting of a small grain crop, the number of tractor passes across the field went from five for conventional tillage to one pass for conservation tillage, with concomitant savings in fuel, labor and equipment costs.

Overall, conservation tillage practices and the cotton-small grain double-crop system increases economic returns to the growers, reduces their labor costs and the number of tractors they need to farm, and saves money in controlling pink bollworm.

Funding Agencies: 

Hatch Act; USDA Western Region Sustainable Agriculture Research and Education grant ; Arizona Grain Research and Promotion Council

Conact Name: 
William B. McCloskey
Contact E-mail: 
Contact Address: 

The University of Arizona

PO Box 210036

Tucson, AZ 85721-0036

(520) 621-7613 office (520) 621-7186