• Unsoaked coated seed used successfully in aerial sowings.
• Herbicide-coated seed proved feasible for one-operation seeding and weed control.
• Short-statured line yielded 7 to 12 cwt/A more grain than taller line 70/3597 at corresponding nitrogen fertilizer and weed populations.
• Rice farm advisors conduct 14 rice variety tests in 9 counties in 1975.
• Short stature and stiff straw give Calrose 76 a greater yield than other late varieties.
• Winter rice-production schools attract 1150 people.
• Shear-bar-type chopper proves best again on rice straw.
• Under good conditions standard 3-wire pulled baler has about 20% greater capacity than big-roll baler.
• Preliminary survey of rice drying systems completed.

INTEGRATION AND IMPROVEMENT OF AGRONOMIC PRACTICES

This project, headquartered at the Rice Experiment Station, Biggs, is directed by UCD scientists. For weed-control research contributed by this project see page 15. Other objectives follow:

1. To evaluate new systems of rice culture so that improved crop management practices are integrated for maximum production efficiency of standard and improved varieties.
2. To develop new or alternative crop management practices, or combinations of them, that are likely to improve stand establishment, growth, yield, and grain quality while minimizing management problems, costs, and energy requirements.
3. To determine the agronomic requirements of short-stature varieties for culture and pest protection, and to develop management systems for optimum yield, chemical efficacy, and economy of fertilizer and water.
4. To investigate the morphological, physiological, cultural, or environmental factors affecting the responses of rice genotypes to herbicides and other agricultural chemicals.
5. To develop techniques of low-altitude aerial observation and photography for detection of cultural or management problems and the distribution of weeds and algae in fields.

NEW CULTURE SYSTEMS

þ Aerial sowings of dry-coated rice seed at 75 to 100 lb/A produced more uniform stands with less seedling drift than sowings of presoaked seed at higher rates, and they also gave very good yields. In an 11-acre field, coated S6 sowed at only 59 lb/A yielded 58 cwt/A of dry rough rice. An economical seed-coating process using continuous-coating machinery is being commercially developed at Pleasant Grove for trials in 1976.

The trials of herbicidal seed coatings have confirmed the feasibility of using coated rice seed as a "granular" herbicide carrier (see photo below). This should lead to planting and weed control in a single operation. Seed with coatings containing the new herbicides (Drepamon or NTN4725, or combinations of Drepamon and Simetryn or NTN4725 and Simetryn) gave as good watergrass control as separate postflood applications of Ordram 10G, with similar increases in grain yield. The possible use of Drepamon and Simetryn in seed coatings should support their continued development as separately applied rice herbicides.

Unsoaked herbicide-coated seed was used to sow plots in foreground. Note good stands and absence of watergrass. Plots at rear were sown with soaked untreated seeds. Note dense population of watergrass.

ALTERNATIVE CROP MANAGEMENT PRACTICES

Water-management for submersed weed control was found to be less critical following Hydrothol-191 applications than with Simetryn. Granular Hydrothol-191 applied 38 days after seeding at 2 or 3 lb ai/A required a static-water period of only 3 days for excellent control of southern naiad, whereas granular Simetryn at 1 or 2 lb ai/A required more than 5 days. Although Simetryn was slow to act on naiad, it killed California arrowhead, ducksalad, water hyssop, waterplantain, monochoria, and roughseed bulrush when applied 38 or 48 days after seeding.

Southern naiad control by granular Hydrothol-191 increased grain yield 7 cwt/A where no urea topdressing was applied, but by only 6 and 4 cwt/A where urea-nitrogen was applied at 27 and 54 lb/A, respectively. Thus, nitrogen topdressing appeared to offset the competitive effects of southern naiad to some extent. Hence, chemical control of this weed might become less profitable at higher rates of nitrogen topdressing.

FERTILIZER X WEED-CONTROL MANAGEMENT OF SHORT-STATURE RICE VARIETIES:

Data from an experiment on interactions of plant height, nitrogen fertility, and weed control support the following provisional conclusions: 1) at corresponding basal nitrogen fertilizer rates, the short-statured line 74-Y-47 yielded 7 to 12 cwt/A more grain than the intermediate-height line 70/3597 in plots both with and without adequate weed control; 2) at each nitrogen level, weed control increased yields by nearly the same amount in each variety, with the increases greatest where nitrogen was low and least where nitrogen was high; and 3) high nitrogen fertilizer can compensate for yield losses from poor weed control in both of these rice lines, for both appear to become more competitive with weeds as nitrogen rate 18 increased.

RESEARCH BY COOPERATIVE EXTENSION AND UCD DEPARTMENTS ON IMPROVED PRODUCTION SYSTEMS

This project is strongly oriented toward field research. Most of it involves both Extension and research-department personnel, working on a coordinated basis to solve local problems and to field-test new ideas.

STANDARD STATEWIDE RICE VARIETY TESTS BY MATURITY GROUP:

In cooperation with the Rice Experiment Station and USDA plant breeders, 14 Standard Rice Variety Tests were conducted in nine California counties in 1975 by Cooperative Extension workers. The results of these combine-size field tests begin on page 5.

þ UNIFORM TESTS OF AGRONOMIC RESPONSE TO NITROGEN:

Four experiments to determine the responsiveness of tall and short-stature rice varieties to fertilizer nitrogen were conducted for three early- and three late-maturity lines in four different environments. The results clearly show that environment greatly affects the plant response of all tested lines to fertilizer nitrogen. Although the early-maturing tall lines S6 and M5 and the short-stature 4963 responded similarly in both warmer and cooler locations the response of short 4963 to added nitrogen was much less in the cooler location. The reason was sensitivity to low temperature. Conversely, short 4963 yielded well and showed a high response level in the warm location. M5 and S6 appear more widely adapted to California climate than the short-statured 4963 line.

The late-maturing lines D7 and CS-M3 responded to fertilizer nitrogen similarly at both locations tested. The long-grain line 72/3764 responded similarly to D7 and CS-M3 in an infertile continuous rice soil in Glenn County, but differed from those lines in a very fertile soil in the Sutter Basin by reaching a maximum yield response at 150 pounds nitrogen per acre. An additional 30 pounds per acre depressed yields of 72/3764 in this environment. The overall data indicated that D7 had a greater yield potential in most areas than the other late lines, probably because of its shortness and greater resistance to lodging.

þ DETERMINING MORE EFFICIENT RATES AND METHODS OF NITROGEN APPLICATION:

1) An experiment was conducted to determine the most efficient rate and method of nitrogen application to rice. Tagged nitrogen ¹⁵N was used to follow the applied nitrogen in the plant. Assays of ¹⁵N in the plant tissue and grain determined the amount of fertilizer nitrogen that actually gets into the rice plant. Utilization of fertilizer nitrogen by the plant proved most efficient when all the nitrogen was applied preplant. Second-most efficient was for 2/3 of total nitrogen applied preplant and 1/3 topdressed at panicle initiation or the early boot stage. See page 37 for details.

2) Another experiment was conducted on the shallow red San Joaquin soil series, characterized by relatively shallow hardpan. Although it is known that some red terrace soils have a general history of nitrogen and phosphorus requirements, it appears that potassium is becoming a yield-limiting factor in more areas. This experiment was established to determine why yields of rice were low the previous two years in this particular district. Rates of nitrogen, phosphorus, and potassium were varied to study their influence.

Plant growth responses from added nitrogen, phosphorus, and potassium were later reflected in increased grain yield. Because of field variability there was no statistical significance between some of the treatments, though the trends were consistent.

 

Table 3. 1975 Yuba County rice fertilizer experiment
Yield in pounds rice per acre
	P0K0	P80	K90	P80K90
N0	4500	---	---	---
N50	5300	---	---	---
N100	5700	5900	6200	6400
The subscript number = pounds of nitrogen (N), P205 (P), or potassium (K20) applied per acre preflood.

RESPONSES TO NITROGEN AND PHOSPHORUS BY ANZA WHEAT FOLLOWING RICE:

An experiment was established to determine optimum rates of nitrogen and phosphorus for wheat following rice. The soil was a Sacramento clay that had been in rice for three years. Sacramento clay is a relatively fertile rice soil, and crops planted after rice have not shown the great response to banded phosphorus that the red soil types show. The data so far indicate that wheat following rice requires extremely high nitrogen rates for yields to be maximum.

BACKUP SUPPORT BY COOPERATIVE EXTENSION:

The Cooperative Extension rice combines stationed at UCD were used to harvest 4,316 rice plots from Butte to Kern County. They harvested all the variety tests and the nitrogen x variety tests, and assisted in harvest of experiments by Weed Control, Plant Pathology, and Agronomy. A two-man crew was assigned to each combine through the 1975 harvest season (September 20 to November 3). The harvesters were transported a total of 5,400 miles during the harvest season.

EDUCATIONAL ACTIVITIES:

UC Cooperative Extension state and county staffs participated in extensive rice educational activities in 1975. These activities generally fell into the following broad categories: annual winter grower meetings; periodical newsletters; field calls relating to rice production problems; and preparation of rice publications and popular articles.

A winter Rice Production School was conducted in three locations in cooperation with local rice farm advisors in 1975. The school involved nine presentations to the California rice industry of the most advanced research information on rice varieties, plant protection, and plant nutrition. The information was made available also in a publication financed partially by the Rice Research Board. A total of 1150 rice growers and industry people attended the three session schools, and 1750 copies of the publication have been distributed. Additionally, two rice meetings were conducted in the San Joaquin Valley, emphasizing subjects applicable to the specific areas where the meetings were held. Cooperative Extension staff also participated in organization and conduct of the Rice Field Day at Biggs.

UC's Dr. Donald E. Seaman demonstrated method of coating rice seed to growers attending the 1975 Rice Field Day. Field trials of coated seed sown by aircraft resulted in good stands, high yields, and avoided problems associated with seed-soaking. Techniques are being developed to add herbicides to these coatings for combined planting and weed control.