CHAPTER 4: EFFECTS OF A NEEM-AMENDED PRODUCT AND A SUCCESSIVE
4.3. RESULTS
4.3.1 Beneficial nematode data from 250 ml soil
Beneficial nematodes were grouped into trophic levels for statistical analysis at the first 3 sampling intervals. The diversity and population densities recorded in the soil were for fungivores, bacterivores and omnivores. The total counts for beneficial nematodes were also subjected to One-way and Repeated Measures ANOVA.
4.3.1.1 Total beneficial nematode counts from soil
No significant differences were evident among the treatments for sampling intervals 1 and 3 (Table 4.2). Significant differences were evident among the treatments for sampling interval 2, where treatments 1 and 8 differed significantly from treatments 4 and 5. A significant interaction existed for treatments x sampling times, indicating that total beneficial soil nematode population densities differed between some treatments and sampling times. Population densities of these beneficial soil nematodes increased over time for all treatments except for treatment 4, with the highest abundance evident during sampling interval 3.
Population densities for total beneficial soil nematodes in 250 ml soil samples were relatively high, before the commencement of treatment applications and planting activities (Pre-plant sampling interval), ranging from 694 to 2213/250 ml soil (Table 4.2). At 10 weeks after crop emergence (WAE; Sampling interval 2), only plots treated with treatments 4 or 5 showed a decline in population densities, which differed significantly from the nematode numbers in treatments 1 and 8. By the harvest sampling date, (19 WAE; Sampling interval 3) all the treatments showed an increase in beneficial soil nematode counts which did not differ significantly from each other. Only treatment 8 increased significantly over time.
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Table 4.2: Totals of beneficial nematode population densities in 250 ml soil. (Significance level for Repeated measures ANOVA in capital letters; different letters indicate significant differences across rows for sampling intervals; different small letters per column indicate significant differences among treatments per individual sampling interval).
Treatment Treatment names Sampling interval 1:
Pre-plant
Sampling interval 2:
10 WAE
Sampling interval 3:
19 WAE (Harvest) 1 Untreated control 2.911 (950)2 aABC 3.43 (3325) bC 3.4 (3038) aC
2 Nemacur® 400 EC,
Fenamiphos @ 400 g / L, IRAC: 1B
2.94 (1050) aABC 3.13 (1581) abBC 3.39 (2863) aC
3 Nemacur® 400 EC + Kalahari 3:1
2.46 (694) aAB 3.26 (2419) abABC 3.26 (2238) aBC 4 Nemacur® 400 EC +Velum®
Prime 400 SC
3.2 (2213) aBC 2.91 (950) aABC 3.17 (2000) aABC 5 Nemacur® 400 EC +Velum®
Prime 400 SC + Kalahari 3:1
2.92 (1131) aABC 2.83 (731) aABC 3.12 (1663) aABC 6 Velum® Prime 400 SC,
Fluopyram @ 400 g / L, IRAC:
25; FRAC: 7
2.93 (988) aABC 3.26 (2300) abBC 3.3 (3306) aBC
7 Velum® Prime 400 SC + Kalahari 3:1
3.18 (1738) aABC 3.2 (2006) abBC 3.38 (2638) aC 8 Kalahari 3:1, organic fertiliser 2.34 (1013) aA 3.44 (3256) bC 3.51 (3788) aC
F-ratio: 1.597 4.526 1.402
P-value: 0.155 0.000 0.223
Interaction: Treatments x Sampling intervals
F-ratio: 2.47
P-value: 0.004
1Log-transformed mean of nematode population density; 2Real means of nematode population density.
4.3.1.2 Bacterivore nematode counts from soil
Statistically significant differences were observed between treatments 3 and 7 (with significantly higher bacterivore abundance) at pre-plant, while treatment 8 differed significantly from all the other treatments with the highest mean of bacterivores observed at WAE. No significant differences were observed between treatments at the harvest sampling interval (Table 4.3). Over the three sampling intervals, significant interaction was evident for treatments 1 and 3. The abundance of bacterivores for treatments 1 and 3 at pre-plant were significantly lower than that of sampling intervals 2 and 3.
Population densities of bacterivores in 250 ml soil were high at pre-plant (sampling interval 1), ranging from 203 to 1669/250 ml soil (Table 4.3). Population densities generally increased at 10 WAE (sampling interval 2), except for treatments 4 and 5, ranging from 650 to 2563/250 ml soil.
Population densities increased at harvest (sampling interval 3) as well, ranging from 1469 to 3494/250 ml soil.
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Table 4.3: Bacterivore nematode population densities in 250 ml soil. (Significance level for Repeated measures ANOVA in capital letters; different letters indicate significant differences across rows for sampling intervals; different small letters per column indicate significant differences among treatments per individual sampling interval).
Treatment Treatment name Sampling interval 1:
Pre-plant
Sampling interval 2:
10 WAE
Sampling interval 3:
19 WAE (Harvest) 1 Untreated control 2.131 (641)2 abAB 3.23 (2239) aC 3.23 (2025)aC 2 Nemacur® 400 EC,
Fenamiphos @ 400 g / L, IRAC: 1B
2.81 (880) abBC 3.09 (1456) aBC 3.32 (2556) aC
3 Nemacur® 400 EC + Kalahari 3:1
1.55 (203) aA 3.21 (2213) aC 3.23 (2100) aC 4 Nemacur® 400 EC +Velum®
Prime 400 SC
2.90 (1669) abBC 2.83 (744) aBC 3.04 (1638) aBC 5 Nemacur® 400 EC +Velum®
Prime 400 SC + Kalahari 3:1
2.40 (756) abABC 2.79 (650) aBC 3.06 (1469) aBC 6 Velum® Prime 400 SC,
Fluopyram @ 400 g / L, IRAC:
25; FRAC: 7
2.73 (615) abBC 3.17 (2050) aBC 3.16 (2763) aBC
7 Velum® Prime 400 SC + Kalahari 3:1
3.05 (1469) bBC 2.96 (1188) aBC 3.23 (1906) aC 8 Kalahari 3:1, organic fertiliser 2.64 ( 938) abBC 3.29 (2563) bC 3.45 (3494) aC
F-ratio: 2.356 2.783 1.286
P-value: 0.035 0.015 0.274
Interaction: Treatments x Sampling intervals
F-ratio: 2.60
P-value: 0.003
1Log-transformed mean of nematode population density; 2Real means of nematode population density.
4.3.1.3 Fungivore nematode counts from soil
Significant differences were observed at 10 WAE only, which was evident between treatments 2 and 3 differing significantly from treatment 1 (Table 4.4). There were no statistically significant differences between treatments at the pre-plant and harvest sampling intervals, nor were there any significant interactions between treatments x sampling intervals. This indicates that, overall, fungivore population densities were similar for most treatments and sampling times, although they increased over time for treatments 1, 2, 4, 6 and 7 but not for treatments 3, 5 and 8.
Fungivore population densities in 250 ml soil were moderately low, ranging from 100 to 488/250 ml soil at pre-plant (sampling interval 1) (Table 4.4). Population densities increased slightly at 10 WAE (sampling interval 2), ranging from 81 to 1004/250 ml soil. Population densities at harvest (sampling interval 3) generally remained similar to that at 10 WAE, ranging from 106 to 950/250 ml soil.
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Table 4.4: Fungivore nematode population densities in 250 ml soil. (Significance level for Repeated measures ANOVA in capital letters; different letters indicate significant differences across rows for sampling intervals; different small letters per column indicate significant differences among treatments per individual sampling interval).
1Log-transformed mean of nematode population density; 2Real means of nematode population density.
4.3.1.4 Omnivore nematode counts from soil
Statistically significant differences were only observed at pre-plant, with treatments 2 and 3 differing significantly from treatment 7 but not from the others (Table 4.5). No statistically significant differences were observed for omnivore nematodes between treatments at 10 WAE and harvest sampling intervals. Some significant interactions did exist between treatments x sampling intervals. Treatments 2 and 3 at pre-plant and treatments 4 and 5 at 10 WAE differed significantly from treatment 7 at pre-plant. Population densities varied over time.
Omnivore population densities in 250 ml soil varied, ranging from zero to 263/250 ml soil at pre- plant (sampling interval 1) (Table 4.5). Population densities declined at 10 WAE (sampling interval 2), ranging from zero to 81/250 ml soil. A slight increase was observed in population densities at harvest (sampling interval 3), ranging from six to 88/250 ml soil.
Treatment Treatment name Sampling interval 1:
Pre-plant
Sampling interval 2:
10 WAE
Sampling interval 3:
19 WAE (Harvest) 1 Untreated control 2.111 (250)2 aA 2.89 (1004) bA 2.26 (950) aA
2 Nemacur® 400 EC,
Fenamiphos @ 400 g / L, IRAC: 1B
1.91 (176) aA 1.34 (113) aA 1.57 (219) aA
3 Nemacur® 400 EC + Kalahari 3:1
2.31 (488) aA 1.36 (156) aA 1.54 (106) aA 4 Nemacur® 400 EC +Velum®
Prime 400 SC
1.68 (194) aA 1.47 (206) abA 2.46 (350) aA 5 Nemacur® 400 EC +Velum®
Prime 400 SC + Kalahari 3:1
1.85 (269) aA 1.46 (81) abA 1.72 (188) aA 6 Velum® Prime 400 SC,
Fluopyram @ 400 g / L, IRAC:
25; FRAC: 7
1.46 (210) aA 1.97 (194) abA 1.92 (456) aA
7 Velum® Prime 400 SC + Kalahari 3:1
1.32 (100) aA 2.68 (813) abA 1.87 (688) aA 8 Kalahari 3:1, organic fertiliser 1.85 (256) aA 2.5 (644) abA 1.34 (256) aA
F-ratio: 0.719 3.681 0.848
P-value: 0.656 0.002 0.552
Interaction:
Treatments x Sampling intervals
F-ratio: 1.615
P-value: 0.086
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Table 4.5: Omnivore nematode population densities in 250 ml soil. (Significance level for Repeated measures ANOVA in capital letters; different letters indicate significant differences across rows for sampling intervals; different small letters per column indicate significant differences among treatments per individual sampling interval).
Treatment Treatment name Sampling interval 1:
Pre-plant
Sampling interval 2:
10 WAE
Sampling interval 3:
19 WAE (Harvest) 1 Untreated control 0.971 (59)2 abAB 0.61 (81) aAB 0.83 (63) aAB
2 Nemacur® 400 EC,
Fenamiphos @ 400 g / L, IRAC: 1B
0 (0.0) aA 0.43 (13) aAB 1.27 (88) aAB
3 Nemacur® 400 EC + Kalahari 3:1
0 (0.0) aA 0.57 (50) aAB 0.3 (31) aAB 4 Nemacur® 400 EC +Velum®
Prime 400 SC
1.34 (263) abAB 0 (0.0) aA 0.43 (13) aAB 5 Nemacur® 400 EC +Velum®
Prime 400 SC + Kalahari 3:1
1.01 (63) abAB 0 (0.0) aA 0.21 (6) aAB 6 Velum® Prime 400 SC,
Fluopyram @ 400 g / L, IRAC:
25; FRAC: 7
1.44 (169) abAB 0.33 (56) aAB 1.12 (88) aAB
7 Velum® Prime 400 SC + Kalahari 3:1
1.8 (213) bB 0.21 (6) aAB 0.52 (44) aAB 8 Kalahari 3:1, organic fertiliser 1.41 (119) abAB 0.53 (50) aAB 0.91 (38) aAB
F-ratio: 3.322 0.72 1.279
P-value: 0.005 0.655 0.278
Interaction:
Treatments x Sampling intervals
F-ratio: 1.97
P-value: 0.026
1Log-transformed mean of nematode population density; 2Real means of nematode population density.