|Fertilization - 71
þ UNIFORM FERTILIZER APPLICATION IS NEEDED
Rice yields have been seriously reduced where fertilizer is not applied uniformly. Rice yields may vary as much as 400% across a single swath applied by air or ground rigs. Spinner-type spreaders for fertilizers and other granular materials have given better results than ram-type spreaders. Swath patterns are wider and of a shape that provides more uniform distribution.
SUPPLEMENTARY NITROGEN BOOSTS YIELDS
Field experiments indicate that too much nitrogen top-dressed after the main tillering period may increase the number of nonbearing tillers. If nitrogen is still needed after the initial application, top-dressing at panicle initiation improves yields by increasing the a number of spikelets per panicle and producing heavier seeds.
þ DETERMINE FERTILIZER NEEDS FROM PLANT ANALYSIS
In 424 California fields sampled, plant analysis showed that 23% would have obtained higher yields with more nitrogen, 11% needed more phosphorus, and about 1% needed potassium. Plant analysis has been demonstrated to be an effective means of getting the greatest benefits from fertilizers, and also avoids overfertilization, which also depresses yields.
þ NITROGEN USE IS GREATLY AFFECTED BY TIMING
In '71 as before, very best results came from applying all nitrogen right off, preplant. Sometimes there are reasons not to (because of seasonal growing differences and management practices in a particular district). If so, apply 2/3 preplant, and 70 to 80 days later (at panicle initiation) apply 1/3 as a top dressing. Nitrogen placement depth in preplant should be 2 to 4 inches.
þ FASTER WORD ON NITROGEN NEEDS COMES FROM NEW TEST
A new UC Davis colorimetric plant-analysis test for nitrogen replaces the slower (and more expensive) Kjeldahl method for determining rice needs. Commercial laboratories can now give you faster nitrogen tissue analysis. Tissue test information should ultimately cost less too.
þ CUSTOM-DESIGNED FERTILIZATION PROGRAMS
Preplant laboratory analysis of soils and growing-season tissue analysis make it possible to custom-design your rice fertilization for time of year, variety, and the individual field. Progress continues toward faster diagnosis. May be only a couple of years away if research continues successful toward tissue tests that can be made right in the field.