All trials were conducted as paired plots that were sub-sampled to replicate the observations. This experimental design made it difficult to obtain equal initial weed densities for both cultivation treatments. For instance, in broccoli trials 1 and 2, the brush hoe plots began with 2.86 and 1.96 times the weed density of the conventional cultivation plots, respectively. However, the final weed densities for the brush hoe in broccoli trials 1 and 2 had 2.72 and 2.86 times the weed densities, respectively. These results make interpretation difficult, but they seem to indicate that the two cultivators have comparable weed control efficacy, which is logical given that the brush hoe and the conventional cultivator used in these two trials leave uncultivated strips of nearly equal widths, 2 7/8 and 3 inches wide, respectively. The brush hoe had clear a clear advantage over conventional cultivation where weed densities are high (i.e. 12.9 to 27.3 weeds/foot), as in the kale trial. In this example the brush hoe reduced thinning/weeding time per acre by 4.1 hours, which if total labor costs are $10.00/A the saving would be $41.00 per acre. However, in head lettuce trial No. 1 weed densities ranged from 9.1 to 10.3 weeds per foot of row and no significant savings in weeding times were seen.
Transplanted crops present a different scenario to weeding crews. The transplants must be hoed around rather than relying upon the rhythmic action of the hoe used in thinning/weeding operations. This is substantiated by the fact that there were poor to weak correlations between weed densities, either weeds/m2 or per foot of row, in transplanted crops. All three trials with transplanted crops had very low weed densities, ranging from 1.3 to 2.1 weeds per foot. Given these scenarios however, there was a general increase in the time to weed conventionally vs. brush hoe cultivated plots, but the savings were less than 2 hours per acre, yielding less than $20.00 per acre savings.
The key issue for the adoption of the brush hoe as an improvement in weed- control efforts by organic growers is the efficiency and economics of its use. Conventional cultivators in the Salinas Valley typically travel at speeds of 4-5 miles per hour and can cultivate up to 45 acres per day. In the trials that we conducted the top speed that we traveled was 2.5-3 miles per hour. In addition, the brush hoe required an additional driver to steer the implement to allow for close cultivation. Close cultivation can be achieved with conventional cultivation as well, but at reduced speeds. An advantage that the brush hoe provides is that the action of the brushes do not shear and fracture the soil as can occur when cultivation knives and sweeps pass through the soil. We were not able to measure relative yields in these trials, but nci obvious differences in growth and yield were observed between the brush hoe and conventional cultivation. The brush hoe may have more applicability to small operations that have minimal access to hand labor where close cultivation may pay off in time and money saved in subsequent weeding operations, These trials indicated that it clearly can save the grower money under high weed pressure.
The following are comments that growers made regarding the brush hoe: • Needs a hydraulic motor, because of constraints of the PTO system It may have advantages for 80- inch bed culture • Organic lettuce growers frequently use transplants to reduce problems with lettuce aphid and the brush hoe may have trouble cultivating close to these larger plants • Standard cultivators are designed to adjust to the heights of individual beds, however the brush hoe has a shaft that spans the beds and had trouble adjusting to uneven beds • It did not tear the bed down as much on the first cultivation which may be a advantage • It did not seem to have problems with heavy and/or wet soils conditions Outreach: The brush hoe was demonstrated at the 1999 and 2000 U.C. sponsored Salinas Valley Weed Day (July 20, 1999 and July 26, 2000, respectively). Results of the brush hoe trials were discussed at the Salinas Valley Weed School (November 29, 2000); the Agricultural Conference and Trade Show in Gilroy (December 14, 2000); the California Weed Science Society meeting in Monterey (January 8, 2001) and the Salinas Valley Commodity Series: Cole Crops (January 16, 2000). The brush hoe trials were reported in an article in the Monterey County Crop Notes newsletter (see attached) and in Ag Alert (September, 2000).