• Conservation Tillage Effects on Infiltration and Irrigation Advance Times

      Martin, E. C.; Adu-Tutu, K. O.; McCloskey, W. B.; Husman, S. H.; Clay, P.; Ottman, M.; Tronstad, Russell; Husman, Steve; Norton, Randy; University of Arizona, Tucson, AZ (College of Agriculture, University of Arizona (Tucson, AZ), 2005-05)
      Field experiments were initiated at sites in Marana, Coolidge and Goodyear, Arizona, in the Fall of 2001, in a cotton-based, conservation tillage project. In the 2002 cotton season, following cover and grain crops, soil and water management assessments were made to evaluate the impact of conservation tillage on surface irrigation performance. An additional site was added in the winter of 2002 at Maricopa, Arizona. Analyses included soil texture, infiltration rate and water advancement. At Coolidge, the Conservation plots had higher infiltration rates and longer advance times than the Conventional plots in 2002, 2003 and 2004. At Marana, infiltration rates were initially higher for the Conservation plots but the rates converged at the end of four hours in 2002. In 2003, the Conventional plots infiltrated about one inch more and the opposite occurred in 2004, where the Conservation plots infiltrated about 1 inch more than the Conventional. The advance times for Marana showed the water in the Conventional wheel rows to be the fastest. At Goodyear, the Conservation plots infiltrated more than the Conventional plots in 2002. This also resulted in a slower advance time for the Conservation plots. In 2003, due to tillage by the grower, treatment effects could not be compared and the site was abandoned in 2004. At Maricopa, the Conservation plots infiltrated almost 2.2 inches more water than the Conventional plots and the water reached the end of the field three hours ahead of the fastest Conservation plot in 2003. In 2004, the Conservation plot infiltrated just over 1½ inches more water than the Conventional plots with the Conventional plots having faster advance times. Seasonal irrigation water applications to each treatment were relatively equal for all the sites with the exception of Coolidge. Here, the long field combined with sandy soil made it difficult to adequately irrigate the Conservation plots. In 2002, an additional 21 inches of water was applied to the Conservation plots. In 2003, that amount was reduced to 12.5 inches. The 2004 irrigation data are not yet available. The yield data show a significant difference between years and different sites. In 2002, only the yields measured at Coolidge were significantly different with the Conservation yielding higher than the Conventional. This may have been due to the increase water application. In 2003, the opposite occurred and the Conventional plots yielded more than the Conservation plots. This may have been due to herbicide damage. At Maricopa the Conventional plot also yielded more than the Conservation plot in 2003 but there was no measured difference in 2004. The Marana site had equal yields for both treatments except for the final year, 2004, when the Conventional yielded higher than the Conservation treatment. Indications are that conservation tillage does impact irrigation performance and it may not be suitable for all locations depending on soil type and field layout.
    • Weed Management and Agronomic Performance of a Cotton-Barely Double Crop Rotation

      Adu-Tutu, K. O.; McCloskey, W. B.; Husman, S. H.; Clay, P.; Ottman, M. J.; Martin, E. C.; Teegerstrom, T.; Tronstad, Russell; Husman, Steve; Norton, Randy (College of Agriculture, University of Arizona (Tucson, AZ), 2005-05)
      The tillage operations required to grow an annual barley and cotton crop rotation were reduced by eliminating tillage prior to planting cotton, eliminating cultivations for weed control in cotton, and especially by eliminating tillage following cotton. A light activated, weed sensing automatic spot-spray system reduced the amount of spray volume and herbicide used by 40% to 60% at Marana and 36% to 56% at Maricopa in 2004. At Maricopa, a large number of volunteer cotton plants in the furrows of early planted no-till cotton reduced the spray volume savings from using the weed sensing automatic spot-spray system. Weed control was similar with the weed sensing, automatic spot-spray system compared to the conventional continuous spray system for most weed species but weeds with narrow leaf, upright leaf canopies such as sprangletop, barley and skeleton weed were more difficult to detect and control. In both Marana and Maricopa, there were yield differences between treatments related to planting date, with late-planted cotton yielding less than early-planted cotton. At Marana, the early-planted conventional tillage cotton out-yielded the barley cover crop, early-planted no-till cotton treatment. At Maricopa, there were no yield differences between the two early planted cotton treatments; however, the late-planted conventionally tilled cotton yielded 28% more than the late-planted no-till cotton. Although the yield comparisons are not yet definitive, it appears that in some situations no-till cotton may yield less than conventionally tilled cotton. At Maricopa, the height of cereal crop stubble did not affect subsequent cotton establishment, field populations, plant height or lint production (2003 and 2004) and the position or node of the first fruiting branch and the first retained boll were similarly unaffected in 2004.