Project Leader and Principal UC
Dept. of Agronomy and Range Science, UC Davis
Broadbent, Dept. of Soils and Plant Nutrition, UC Davis
The following are highlights of the findings from this research:
Coated rice seed (left) and uncoated seed. Dr. D.S. Mikkelsen from UCD
continued coating studies in 1980. Coating rice seed with calcium peroxide
and fungicides may make it possible to eliminate the preplant seed soak
operation. It may also lead to the use of preflood application of herbicides
to control weeds.
- Calcium peroxide as a seed coating is a satisfactory oxygen extender,
which when used at a 30 percent seed weight, successfully provides emergence
of rice seed through 2.5 centimeters of soil and 10 centimeters of water.
- Degradation of calcium peroxide coated on rice seed is affected by soil
pH, soil organic matter levels, microbial activity in the soil and heavy
metal catalysts. Use of lime with peroxide retards degradation.
- In a statewide evaluation of the phosphorus status of California rice
soils, about 18 percent of the area sampled showed need for phosphorus
- Soil test comparisons and calibrations from preliminary greenhouse-laboratory
experiments indicate that the sodium bicarbonate-phosphorus extraction test
(dry soil basis) correlates well (0.8937) with plant phosphorus responses. A
critical value of 6 parts per million extractable phosphorus is recommended
for soil test evaluations.
- The partial efficiency of phosphorus applied to rice is highest when
fertilizer phosphate is applied at time of planting. Seedling growth
stimulation is better from broadcast phosphate, but grain yields were not
affected by method of application. Unincorporated broadcast phosphorus will
also stimulate weed seedlings, particularly barnyardgrass.
- Preliminary critical values for evaluating the sulfur status of California
rice varieties suggest that 0.15 percent sulfur is the critical value for
plants in the mid-tillering stage.
- In deficiency situations, phosphate can
be top-dressed on rice until the panicle stage with some yield benefit, but
response declines with delayed applications up to about 60 days after
- Draining rice fields may cause significant losses of fertilizer
nitrogen through nitrification-denitrification if soils dry to less than
- The nitrification inhibitor, nitrapyrin, used on urea
does not appear to improve nitrogen use efficiency by rice when compared
with untreated urea fertilizer.
Area rice specialist Jack Williams looks on as Cooperative Extension
agronomist Dr. James Hill discusses the Cooperative Extension seed coating
field experiment on the Demeter Company farm. To the left is an extensive
variety test. The coating test proved that even coated seed can be covered too deeply. Farmers and
Cooperative Extension play a vital role in field testing Rice Experiment
Station and University f California research results.