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Interaction of Rate and Time of Nitrogen Application and Weed Control Methods in Upland Rice
Thesis Abstract:
A field experiment was conducted to determine the intersection of rate and time of nitrogen application and weed control methods in two upland rice varieties, IR 2935-242-1 and C 22, grown under upland conditions.
Results showed that IR 2035-241-1, a semi-dwarf IRRI selection, produced more tillers and panicles and less percentage of unfilled grains than C22, a tall, College-recommended upland variety.
Statistical analysis indicated that among the weed control methods used, application of butachlor at 2 kg a,i./ha at pre-emergence followed by handweeding 25 days after rice emergence (DARE), was comparable to handweeding three times in terms of less weed biomass, taller plants, more tillers and panicles, and higher grain yield.
Increasing rates of nitrogen application resulted in shorter period of panicle initiation and blooming days, taller plants, more tillers and panicles, less percentage of unfilled grains, and increase in grain yield.
High net return was obtained with the application of butachlor at 2 kg a,i./ha, followed by handweeding 25 DARE and fertilization with 120 kg N/ha in three split doses, although the highest grain yield was produced from crops handweeded three times with the same rate and time of nitrogen application.