|Stand Establishment &
þ SEED TREATMENT IMPROVES STANDS
Difolatan, one of the most promising test fungicides, or captan, used in proper amounts as a seed treatment, will minimize problems in stand establishment caused by seedling disease, reduce need for reseeding, and provide more uniform stands. Reduced seeding rates are possible with use of seed treatment, saving more than treatment costs. Seeding rates can be safely reduced to a maximum of 125 lb per acre. Using captan in the Evershield CM formulation reduces losses of the fungicide during preplant soaking.
þ DON'T DELAY SEED USE AFTER SOAKING
After a soaking bin is drained, seed temperature rises and oxygen levels decline. Low oxygen (only 1% of gaseous volume within 20 hr of draining) can inhibit seedling development if the seeds are left in that state for 72 hr. But even before that (48 hr after draining) the temperature in the bin gets close to the killing temperature of 105°F.
So: plant the drained seed as soon as possible after draining is complete, preferably within 24 hr of the start of draining. If north winds or other circumstances delay seeding, reflood with cold water and redrain every 24 to 36 hr until you sow.
SEEDLING VIGOR CHECKED IN 20,000 SELECTIONS
Although many short-stature lines were discarded because of poor stands in cold weather, several seemed to have the vigor of California varieties. The fourth generation of short-statured lines derived from crosses of IR-8 and Hungarian introductions of outstanding vigor are being used in crosses with other promising short-stature lines.
A dry-seeding system involving initial flush or sprinkler irrigation followed by continuous flooding gave good stands that were remarkably free of sedges and broadleafs although annual grasses were much more serious than in water-sown continuously flooded rice. These were small-plot trials.
SEED SOAKING ALTERNATIVES
Seed-coating work continues with the hope of eliminating the cumbersome seed-soaking operation. Materials tried include chemicals to protect against diseases, micronutrients to correct soil deficiencies, and growth-stimulating substances to speed seedling development. The most promising material, activated charcoal, protected significantly against damage from herbicides applied to the seedbed at preplant.
COLD TOLERANCE NOW TESTED EASILY
Seedling cold tolerance, now shown to be heritable, is now tested simply in the lab in screening varieties and selections. Easier, faster, and more accurate than field tests, emergence through about 6 inches of cold water indicates seedling vigor.
BLANKING RESISTANCE SEEMS INHERITED
Lines showed 60% difference in resistance in blanking, making that a good objective in breeding. Added blanking information is coming from the winter nurseries in Hawaii. Some lines have blanked nearly 100% whereas others produced abundant seed. Cause of difference: mainly weather at or before heading, although the lines tested seem to differ greatly. This information should be valuable in breeding for minimum blanking.
BLANKING FACTORS JUST BEFORE HEADING
Panicle blanking varied between varieties but was affected strongly by night temperature in a 5-day period when the plant was very sensitive, 10-16 days before heading, with the developing panicle enclosed in the leaf sheath and about 10 inches long. Three days of low temperatures then increased blanking from 11.4 to 28.5%, and 5 days raised it close to 50%.