SITE INFORMATION AND CORRESPONDENCE_FILE 2

Home Browse Search

%..I California Avocado Society 1956 Yearbook 40: 81-85 WEED CONTROL IN AVOCADO ORCHARDS Boysie E. Day and C. D. McCarty Boysie E. Day is Assistant Plant Physiologist, Department of Horticulture, University of California, Citrus Experiment Station, Riverside. C. D. McCarty is Field Technologist, University of California, Agricultural Extension Service, Riverside. Cultivation in avocado orchards in California is almost a thing of the past. It has been shown that cultivation does not conserve soil moisture, nor does it have advantages in the establishment of a mulch. Since avocados are surface feeders, 'Cultivation injures the trees by the destruction of roots near the soil surface. Cultivation also breaks down soil structure and results in the formation of a plow sole just under the cultivated portion, which retards the penetration of water. Erosion from rainfall and irrigation water is a problem when hillside soils are cultivated. Untilled soils are less subject to erosion. Other than its value for incorporating manures into the soil and preparing irrigation works, cultivation is useful to the orchardist only as a means of controlling weeds. With so few advantages to offset numerous disadvantages, it is understandable that growers have sought means other than tillage for controlling weeds so that cultivation may be eliminated altogether as an orchard practice. In eliminating cultivation, two methods of non-tillage have emerged in avocado orchards. One program allows the development of a sod of weeds between the trees. Weeds are mowed and no effort is made to eradicate them except around young trees to prevent excessive plant competition. Under a mowing program, regardless of the weed population originally present, bermudagrass eventually crowds out other weed species, resulting in a solid bermudagrass sod. The second method calls for the complete control of weeds by means of chemical or oil sprays with the formation of a natural leaf mulch. There are advantages to such a program, since even closely mowed weeds are competitive with the trees. Weeds require the same nutrients as other plants. Weedy species feed aggressively, competing for nutrients needed by the trees. Even more serious is the competition of weeds for water. There is evidence that mowing of a cover crop, such as bermudagrass, does not appreciably reduce its use of water. Water-requirement studies show that it takes about seven hundred pounds of water to produce one pound of dried plant material. Although this varies with plant species, it is known that weedy species are among our most extravagant users of water. A permanent cover crop often uses as much water as the trees. In situations where water is inexpensive and plentiful, it is understandable that weed control in orchards is frequently neglected. However, faced with today's high cost of water, control of weeds in orchards becomes a problem of compelling importance.