A COMPARISON BETWEEN MCPA AND PESCO is-I5 FOR THE ...

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Materials and Methods The experiment was laid out on the Black Akuse Clay soils at Kpong. The land was ploughed, harrowed .and levelled, but was not puddled. Treatment plots (1/57.4 acre each) were enclosed in separate bunds to enable independent flooding. Paddy (variety Nickerie), treated with agrosan at the rate of 1 oz. to 28 lb. seed, was broadcast at the rate of 80 lb. per acre on 20th October, 1964. The' seed was not pre-germinated. The layout. of the experiment was a randomised block design, replicated three times. The treatments consisted of two herbicides: MCP A and Pesco 18-15, applied at two levels each: three pts./ac. and five pts./ac, and applied at two different times: pre-emergence and post-emergence. The~e were compared against weeded and unweeded rice plots. The pre-emergence treatments were applied two days after sowing, on the 22nd October, 1964. The post-emergence treatments were applied on 20th November, 1964 four weeks after sowing. The application of the herbicides was done with a pressurised napsac sprayer operating around a pressure of about 60 lb./sq. inch and at a volume of 30 gallons per/acre. The plots with 'clean weeding' treatment were kept weed free by periodic removal of weeds by hand hoeing. Owing to the difficulty of distinguishing the grassy weed species from the rice crop at the early stages, thorough weeding by hoeing was not possible until later. In the plots with 'no weeding' treatment weeds were allowed to grow with the crop freely throughout the experiment. Observations and Discussion Germination.-Pre-emergence application of the herbicide delayed germination remarkably (see Table 1 below). TABLE 1 EFFECT OF TREATMENTS ON THE GERMINATION OF PADDY I. MCPA at 3pts/ac. Pre-em. II. MCPA at 5pts/ac. Pre-em. III. Pesco 18-15 3pt/ac. Pre-em. IV. Pesco 18-15 5pt/ac. Pre-em. V. MCPA at 3pt./ac. Post-em. VI. MCPA at 5pt/ac. Post-em. VII. Pesco 18-15 3pt/ac. Post-em. VIII. Pesco 18-15 5pt/ac. Post-em. IX. Clean Weeding . . . . X. No Weeding 1. Standard Error of the Mean=± 2.14 2. Shortest Significant Ranges at 5% level p: (Rp) 3. Treatment Means ranked in order (2) 2.97 6.35 IV 23.9 Time of Germination (50 % Thro.) 16 days 16 days 16 days 16 days 6 daysi 6 days I 6 days ~ ~~:~ I 6 daysJ (3) 3.12 6.67 I 34.1 (4) 3.21 6.87 III 36.2 31.6 10.0 ·35.0 16.6 (5) 3.27 7.00 V 71.6 34.1 18.0 36.2 23.9
The germination percentages for the treatments were transformed by the angular transformation (LeClerg et al. 1962) and subjected to an analysis of variance. At the time of assessment the post-emergence treatments had not been applied. For purposes of this comparison, therefore, all treatments other than pre-emergence application should be considered as untreated. The results of this analysis indicated highly significant effects due to treatments. The untreated plots gave a uniform germinanation of about 90 per cent each, while the pre-emergence treated plots gave well below 40 per cent germination. Within the preemergence treatment plots, there was no significant difference in effect due to MCPA and Pesco 18-15 at the same dosage levels, i.e. at 5pts/acre or 3ptsjacre. There were, however, significant differences in effects due to the different dosage levels of application. At the higher dosage rate of 5ptsjacre of either MCPA or Pesco 18-15, there was a more significant depression in total germination. The drastic effect of the herbicide on germination is evidently due to the fact that the broadcast seeds were exposed to direct contact with the herbicide at the time of application. The effect of pre~emergence application is further indicated by the total percentage germination for treated and untreated plots (Table 1 above). There was a considerable drop in the plots with the pre-emergence treated plots. TABLE 2 Tillering.-Tillering was observed in all plots 21 days after sowing, but the degree of tillering differed with the treated and untreated plots. The figures in Table 2 below sho~ the mean number of tillers per plant per plot. These were based on counts from 10 plants taken at random in each plot. These counts were transformed by the square root transformation, using the formula YV+0.5 (LeClerg et al. 1962), and then subjected to an analysis of variance. This showed that differences due to treatment were just significant at the 5 per cent level. Further examination using Duncan's (1955) shortest significant range test revealed that the pre-emergence treatments significantly affected the degree of tillering in the crop. As the post-emergence application had not been applied at the time of assessment it was not strange that post-emergence treatments did not show any significant differences from the "weeded" and "unweeded plots". Flowering.-Flowering was delayed by preemergence application but post·emergence application 4 weeks after planting had no effect on the flowering period. The delay in flowering was about a week, being 108 days for the pre-emergence plots as against 101days for the post.,emergence, hand weeded and unweeded plots. . Crop Health.-The effect of the herbicide application on the general growth of the crop was assessed by guided visual scoring. The scale used is based on the one used by Green & Kalogeris (1963) and is given below as Table 3. EFFECf OF TREATMENT ON NUMBER OF TILLERS PER PLANT (a) Standard Error of the Mean- ± 0.28 (b) Shortest SignificantRange (Rp) p.: (2) (3) (4) (5) (6) (7) (8) (9) (10) 2.97 3.12 3.21 3.27 3.32 3.35 3.37 3.39 3.4 Rp 0.83 0.87 0.90 0.92 0.93 0.94 0.94 0.95 0.9 (c) Ranked Mean of Treatments Post-em Post-em Post-em Clean No Post-em Pre-em Pre-em Pre-em Pre-em Treatment Orig. MCPA 3ptjac 3.7 Pesco 5ptjac 3.7 pesco 3ptjac 4.7 Weeding 4.7 Weeding 5.0 MCPA Pesco Pesco 5ptjac 5ptjac 3ptjac 5.3 8.3 8.3 Pesco MCPA 3ptjac 5ptjac 8.3 11.0 Transf. 2.0 2.0 2.2 2.2 2.3 2.4 2.8 2.9 2.9 3.4
Page 1: A COMPARISON BETWEEN MCPA AND PESCO
Page 5 and 6: was apparently due to the periodic
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