| Popis: |
The experiment was conducted at the Rice Experiment Station near Biggs. The design was a randomized complete block with 21 treatments and 4 replications. Each plot was 0.7 m2 and encircled by 36 cm high aluminum sheeting. The plots were fertilized on 20 Apr with urea at 76 kg nitrogen/ha and with 18-46-0 at 20 kg nitrogen/ha. Copper sulfate at 11.2 kg (AI)/ha was applied 12 May. Ordram 10G at 4.5 kg (AI)/ha was applied on 17 May and Londax at 70 gm (AI)/ha was applied on 18 May. Rice ‘M-202’ was pre-soaked for 22 h, drained for 4h, and hand seeded at 400 seeds per plot. The plots were flooded and seeded on 6 May. The plots were thinned to 128 plants per square meter between 16 May and 25 May. The pre-flood insecticide treatments were applied on 6 May. Post-plant insecticide applications went on 23 May (3-leaf rice stage), 30 May (5-leaf) and 7 Jun (7-leaf). A moderately heavy natural rice water weevil (RWW) infestation was supplemented with hand collected adults on 26 May (4 RWW), 6 Jun (2 RWW), 10 Jun (4 RWW), and 17 Jun (5 RWW/plot). Adult RWW feeding activity was estimated with leaf scar counts on 7 and 15 Jun. Larval densities were evaluated by randomly selecting ten soil cores (9.5 cm diam × 10 cm deep), each containing one plant, from each plot. The cores were washed through a 20 mesh screen (0.9 mm openings) to separate and count the larvae and pupae. Larval counting occurred on 5 Jul and was repeated on 17 Jul. Cored plants were measured for height, root length, number of tillers and leaves, and dry weight of roots and leaves. Plots were harvested on 23 Sep. |
