DISCUSSION
A critical look into the data obtained confirmed the inhibitory effect of rice crop residues on germination and seedling growth of barnyard grass (Table 1). These suppressive actions are believed to originate from the toxic compounds released from the residues, or produced by microorganism activity during residue decomposition (Birkett et al., 2001). As different plant species contain various allelochemicals in various concentrations (Xuan et al., 2004), the degree of growth inhibition observed in this experiment may also be the result of variations in the type and concentrations of allelochemicals among rice varieties. When susceptible plants are exposed to allelochemicals, the seed germination,
60 D.L. Wathugala & A.S. Ranagalage
March 2015 Journal of the National Science Foundation of Sri Lanka 43(1)
Cultivar name Percent inhibition DR PC GP SL LN DW GR Average
Bg38 5 W 19.6 2.8 24.5 59.0 28.2 26.8 Bg 407 -H 5 W 14.2 6.1 20.8 47.7 32.7 24.3 Bg3-5 5 W 21.0 35.5 36.5 54.6 34.7 36.4 Bw 452 4.5 R 17.6 35.9 43.4 55.5 38.0 38.1 Bw 451 4.5 W 16.2 29.7 39.6 54.1 41.8 36.3 Bw453 4.5 W 21.6 34.4 42.8 58.4 36.0 38.7 Bg454 4.5 W 16.1 30.0 34.0 54.6 33.8 33.7 Ld408 4 R 16.9 28.2 25.8 53.2 36.6 32.1 Bw 400 4 R 15.0 32.3 55.3 59.1 40.9 40.5 H-4 4 W 23.0 12.1 24.5 81.3 36.2 35.4 Bg 406 4 R 15.7 37.4 33.3 51.3 31.5 33.8 Bg407 4 W 18.9 10.8 22.6 42.5 29.0 24.8 At402 4 R 18.3 4.4 23.9 63.3 32.4 28.5 At401 4 R 17.9 12.1 23.3 48.9 38.8 28.2 At 405 4 W 15.9 15.7 23.9 60.5 40.0 31.2 Bg403 4 W 27.0 17.1 22.0 56.1 29.3 30.3 Bw 267-3 3.5 W 15.7 23.4 39.6 59.4 37.4 35.1 Bw 361 3.5 R 13.5 30.9 34.6 55.8 34.9 34.0 Bw 363 3.5 W 12.2 12.9 23.3 57.4 32.3 27.6 Bw 367 3.5 W 14.0 6.4 26.4 60.5 40.0 29.5 Ld356 3.5 R 11.0 19.7 24.5 69.0 37.8 32.4 Ld368 3.5 R 13.7 56.5 39.6 61.9 41.1 42.5 Ld355 3.5 W 14.7 43.0 43.4 64.7 44.7 42.1 Bw364 3.5 R 18.3 37.2 43.4 85.8 39.3 44.8 At 362 3.5 R 18.9 44.0 41.5 59.0 34.5 39.6 Bw272-6b 3.5 R 15.6 22.3 23.9 49.1 32.3 28.6 Bw351 3.5 W 19.6 4.0 25.8 89.1 38.8 35.5 Bg 360 3.5 W 24.3 1.1 23.9 53.6 26.7 25.9 At353 3.5 W 18.3 2.7 24.5 52.7 34.3 26.5 Bg359 3.5 W 14.2 18.3 22.6 38.5 33.8 25.5 At354 3.5 W 19.6 -14.6 11.9 67.5 33.0 23.5 Bg358 3.5 W 20.8 9.4 17.6 44.3 32.6 24.9 Ld365 3.5 R 16.2 20.6 21.2 77.0 34.3 33.9 At 308 3 W 2.9 42.4 43.4 82.9 26.4 39.6 Bg 305 3 W 20.3 -7.5 23.3 83.9 30.7 30.1 At306 3 W 17.6 -14.7 5.0 -5.7 33.1 7.1 Bg304 3 W 15.7 -18.3 5.7 50.6 33.8 17.5 At 307 3 W 10.1 14.4 25.2 54.3 30.2 26.8 At303 3 R 16.1 30.1 32.7 56.5 31.9 33.5 Bw302 3 W 23.2 32.4 43.4 53.1 34.8 37.4 CV 18.5 6.9 8.9 2.5 15.6 2.3 LSD (0.05) 5.0 0.7 4.2 0.3 8.8 0.2
a DR - duration in months; PC - pericarp colour; R - varieties with red coloured pericarp; W - varieties with white coloured pericarp; GP - germination percentage; SL - shoot length; LN - leaf number; DW - dry weight; GR - germination rate CV - coefficient of variance; LSD - least significant difference
Table 1: The inhibitory effect of forty (40) rice variety residue mixtures on barnyard grass seedling growth, germination, and germination rate a