Reduced Tillage Systems for Arizona Cotton Growers

Wayne E. Coates and Gary W. Thacker

Abstract

Introduction

Cotton growers in Arizona know that their profitability and survival depend on maintaining high production while minimizing costs. Tillage operations consume about half of the entire seasonal energy budget before the seed is planted. In addition, tillage operations can contribute significantly to soil compaction and dust emissions, resulting in reduced yield and degradation of the environment.

The purpose of this research was to identify alternative tillage methods for cotton; and to document tillage operational data, energy use, time requirements, operating costs and cotton yields over several seasons.

Reduced tillage systems, tested over several years by The University of Arizona, offer energy savings and reduced dust emissions because they are less intensive than conventional systems. Reduced tillage systems are associated with reduced soil compaction, especially when they restrict wheel traffic to set paths in the field, a system known as controlled traffic farming. Reduced tillage systems also reduce field work time requirements because they require fewer passes over the field.

Materials and Methods

The four alternative tillage systems that were compared to a conventional tillage system at The University of Arizona were:

1. Uprooter-Shredder-Mulcher (USM), developed by S. Ben-Dor Automotive Industries. Ltd. of Israel. This is a two-row machine which uproots the stalks with counter-rotating pinch tires, shreds the stalks in a shearbar shredder, and then injects the residue into the soil at the rear of the machine.
2. Sundance System developed by Sundance Farms of Coolidge, AZ. Developed for buried drip irrigation systems, it consists of a ground-powered stalk puller followed by the Sundance disk which mixes the residue into the soil and re-lists the beds.
3. Stalk Puller System developed by The University of Arizona as a method of harvesting the cotton stalks as a biomass fuel feedstock. The stalk puller is similar to the "tyre pullers" used to uproot whole cotton plants in Australia. It is a three-point hitch mounted implement; each row consists of an undercutting blade which severs the cotton tap roots, followed by a pair of hydraulically powered pneumatic pinch tires which uproot the whole cotton stalks. This pulling action, combined with the forward movement of the machine, causes the stalks to be thrown upward and toward the rear of the implement, where they are funneled through a pair of shields to form a windrow. The stalks are then baled with a round baler and are removed from the field. Since the specific energy of cotton stalks compares favorably to that of wood, this has been investigated as a possible source of energy.
4. Modified Conventional System; consisting of stalk shredding, disking with a conventional tandem disk, and rip/listing with a Sundance disk.

Table 1 describes the five systems studied and includes the operational processes and implements used for each

Results and Discussion

Table 2 lists the number of operations, energy requirements, time requirements, dust emissions, operating costs and yield for the alternative and conventional tillage systems. These data were collected from 1987-1994 at The University of Arizona Agricultural Centers in Marana and Yuma. All of the alternative tillage systems required less energy than the conventional. Time requirements were also less for all alternative tillage systems. Although dust emissions averaged highest for the Sundance System, there were no statistically significant differences between tillage systems. This is partly due to the high dust emissions of the power mulcher used in all tillage systems; this tended to mask the differences in dust emissions from other implements. Operating costs were lower for all of the alternative tillage systems. Although cotton yields with all of the alternative tillage systems averaged higher than with conventional tillage, these differences were not statistically significant.

Conclusions

Reduced tillage systems offer savings in energy use, work time, and operating costs without reducing yield Alternative tillage systems merit serious consideration by Arizona cotton growers.

Acknowledgments

This project has been funded by the Arizona Department of Environmental Quality's Air Quality Fund. Machinery was donated by Arizona Drip Systems and Central Machinery Company. Machinery was loaned by Automotive Industries, Ltd., Bob and Dean Wells of Casa Grande, the LDS Church Farm of Marana, and Tom Clark Farms of Marana.

Table 1. Tillage systems tested at the University of Arizona Agricultural Centers in Marana and Yuma.

Table 2. Field data comparison of tillage systems tested at the University of Arizona Agricultural Centers in Marana and Yuma.

Full Disclaimers

Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, James A. Christenson, Director Cooperative Extension, College of Agriculture and Life Sciences, The University of Arizona.

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