Rice Production in California (3/13)
Hill, J.E., S.R. Roberts, D.M. Brandon, S.C. Scardaci, J.F. Williams, R.G. Mutters
Management decisions and practices
Rice production in California is highly mechanized, requiring only about four hours of labor per acre. In contrast, non-mechanized rice production in much of Asia and Africa requires more than 300 hours of labor per acre. Mechanization includes laser technology to precision-level rice land and establish field grades, large tractors and heavy-duty implements to prepare seedbeds, and self-propelled combines with half or full tracks for harvesting in muddy soils. Aircraft are used for seeding, pest control, and some fertilization.
Many management decisions are required throughout the year, including 1) marketing and business planning; 2) field preparation, fertilization, and planting; 3) water, crop, and pest management during the growing season; 4) harvesting, drying, and storage; and 5) postharvest activities, including straw management and other field work.
The Calendar of Rice Operations (fig. 7) shows typical cultural operations and timing used for rice production in the Sacramento Valley. The timing of individual farm operations may differ from the period indicated.
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| Figure 8. Precision laser leveling for a rice-only cropping system leaves the field with a slope of zero to 0.05 feet per 100 feet. |
Land grading and seedbed preparation
Land leveling allows maintenance of a uniform water depth within the basin (check) and greatly facilitates subsequent management practices for stand establishment, weed control, and field drainage for harvest (fig. 8). Precision leveling also improves water use efficiency in rice. Following the adoption of laser leveling technology in the late 1970s, more than 90 percent of California rice land was precision-leveled (fig. 9).
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| Figure 9. Contour levees were used prior to widespread laser leveling of the 1970's and continue to be used where rice is rotated to other crops. Over 90 percent of California's rice acreage is laser leveled (see fig. 18). |
The slope of a field depends largely on the crops produced in the rice-based rotation. In rice-only cropping systems, land may be leveled from a slope of zero grade to 0.05 feet per 100 feet. In rice row crop systems, grades of 0.1 to 0.2 feet per 100 feet are required to provide adequate slope for irrigation of the rotation crop. Precision leveling to zero grade provides maximum control of water depth, but it may result in poor surface drainage and muddy soil conditions during harvest. Conversely, overly steep fields make water depth control more difficult. Precision leveling decreases the number of levees required and increases productive land area and machinery efficiency.
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| Figure 10. Land planes are used on an annual basis to remove high areas that may promote weed growth. |
Field operations begin with disposal or decomposition of the straw, by burning, wet or dry soil incorporation or removal from the field. Crop residue incorporation in the fall hastens straw decomposition and reduces the likelihood of algal growth and toxic gas formation in the following rice crop. Soil tillage dries rhizomes and other underground overwintering structures of perennial weeds. Tillage may be postponed until spring under wet conditions, but generally begins as early as possible.
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| Figure 11a. Large heavy rollers corrugate the seedbed, providing a more uniform seedbed than harrows. | b. The resulting stand may appear to be drill-seeded because the rice seed settles in corrugations. |
Smoothing the soil with laser-directed bucket scrapers or three-wheel planes removes high areas that are sites for rapid weed growth as a result of shallow water. Low areas that reduce rice growth and survival because of deep water are filled. Planing also reduces clod size and provides a more uniform seedbed. The final tillage operation corrugates the soil across the prevailing wind direction to protect the emerging rice seedlings from wind-generated waves. Heavy corrugated rollers are used increasingly as a final field operation to eliminate large clods, pack the seedbed, and corrugate the soil, providing a more uniform seedbed than with harrows (fig. 11). Liquid and dry fertilizer and pesticide applicators attached to the roller allow growers to perform multiple operations at one time (fig. 12).
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| Figure 12. A custom fertilizer applicator with an attached roller allows the completion of several field operations at once. |
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Comments to jayoung@ucdavis.edu