Table 1.
Actual nitrogen application rates by year for the three fertilizer treatments sampled in this study, in relation to rates recommended for blueberry production in British Columbia (BCMAL, 2020).
| Nitrogen application rates (kg N ha–1) | |||||||
|---|---|---|---|---|---|---|---|
| 2009 | 2010 | 2011 | 2012 | 2013 | 2014 | 2015-2019 | |
| 1N | 11 | 14 | 25 | 39 | 100 | 111 | 144 |
| 1.5N | 22 | 29 | 50 | 79 | 151 | 167 | 215 |
| 2N | 32 | 43 | 75 | 118 | 201 | 222 | 287 |
| Recommended | 22 | 29 | 50 | 79 | 100 | 111 | 144 |
Figure 1:
Changes through time in the percentage of samples with Pratylenchus crenatus, Rotylenchus robustus, and Paratrichodorus renifer in the experimental area. At each sample date, a single 100 cm3 sample from each of 24 plots (six replicates of four N fertilization treatments) in the experimental area was analyzed. Blueberry bushes were planted in fall of 2008.
Figure 2:
Effects of fertilizer nitrogen application rates on population densities of Rotylenchus robustus, from September, 2009 through June, 2019. Error bars are one standard error projecting above the 0N control (pooled standard error from overall ANOVA of non-transformed data). Within a date, points labeled with the same letter are not significantly different (p < 0.05) based on Diff procedure in mixed model repeated measures analysis of log-transformed data. NS, no significant differences.
Figure 3:
Effects of fertilizer nitrogen application rates on population densities of Pratylenchus crenatus, from September, 2009 through June, 2019. Error bars are one standard error projecting above the 0N control (pooled standard error from overall ANOVA of non-transformed data). Within a date, points labeled with the same letter are not significantly different (p < 0.05) based on Diff procedure in mixed model repeated measures analysis of log-transformed data. NS, no significant differences.
Figure 4:
Effects of fertilizer nitrogen rates on the abundance of root fragments extracted from soil cores (g roots per kg dry soil), from April, 2016 through June, 2019. Error bars are one standard error projecting above the 0N control. Within a date, points labeled with the same letter are not significantly different (p < 0.05) based on Diff procedure in mixed model repeated measures analysis of log-transformed data. NS, no significant differences.
Figure 5:
Relationships between Rotylenchus robustus population densities and root biomass. Nematode population data and root biomass data for each plot were averages of six sample dates in 2016 and 2017.
Table S1.
Mean (n=6 replicate plots) population densities (nematodes/100 cm3 soil) of free-living nematodes across dates and N fertilization treatments in 2017.
| Date | April 2017 | June 2017 | September 2017 | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Treatment | 0N | 1N | 1.5N | 2N | 0N | 1N | 1.5N | 2N | 0N | 1N | 1.5N | 2N |
| Ditylenchus | 91 (48) | 154 (58) | 109 (33) | 135 (61) | 50 (37) | 147 (240) | 81 (51) | 150 (225) | 96 (38) | 124 (73) | 65 (25) | 73 (37) |
| Acrobeloides | 43 (43) | 104 (77) | 69 (31) | 98 (80) | 41 (28) | 166 (286) | 117 (54) | 109 (97) | 31 (10) | 77 (51) | 81 (24) | 68 (68) |
| Rhabditidae | 23 (18) | 62 (78) | 52 (52) | 39 (42) | 46 (23) | 62 (100) | 26 (23) | 26 (20) | 35 (39) | 16 (13) | 17 (11) | 17 (21) |
| Aphelenchoides | 59 (37) | 66 (68) | 51 (21) | 42 (8) | 22 (16) | 26 (25) | 14 (14) | 19 (21) | 34 (23) | 25 (12) | 15 (13) | 10 (7) |
| Filenchus | 26 (11) | 43 (35) | 22 (17) | 15 (21) | 22 (24) | 8 (5) | 5 (4) | 3 (3) | 27 (26) | 51 (34) | 12 (13) | 4 (6) |
| Cervidellus | 23 (23) | 51 (47) | 28 (39) | 14 (17) | 13 (25) | 42 (72) | 5 (8) | 4 (7) | 16 (13) | 23 (16) | 8 (4) | 5 (6) |
| Alaimus | 9 (10) | 7 (7) | 3 (6) | 1 (2) | 21 (18) | 7 (7) | 13 (10) | 5 (6) | 24 (16) | 15 (19) | 5 (5) | 4 (7) |
| Plectus | 14 (11) | 17 (20) | 19 (13) | 7 (12) | 4 (7) | 1 (2) | 3 (7) | 0 | 9 (9) | 2 (3) | 0 | 2 (5) |
| Clarkus | 4 (10) | 7 (12) | 2 (3) | 0 | 5 (6) | 9 (14) | 1 (3) | 0 | 10 (8) | 12 (24) | 1 (2) | 1 (2) |
| Prismatolaimus | 11 (6) | 9 (12) | 1 (3) | 0 | 3 (5) | 0 (1) | 0 | 4 (8) | 9 (13)) | 1 (3) | 1 (2) | 1 (1) |
| Aphelenchus | 3 (10) | 0 | 1 (3) | 1 (2) | 1 (1) | 6 (15) | 0 | 0 | 1 (2) | 1 (2) | 2 (3) | 1 (2) |
| Teratocephalus | 6 (9) | 1 (2) | 1 (3) | 3 (5) | 0 (1) | 1 (2) | 0 | 0 | 0 (1) | 0 | 0 | 0 |
| Seinura | 1 (1) | 0 | 3 (4) | 0 | 0 (1) | 1 (2) | 1 (3) | 3 (8) | 0 (1) | 2 (4) | 1 (2) | 0 |
| Panagrolaimidae | 1 (2) | 5 (13) | 2 (3) | 2 (5) | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 (2) |
| Thonus | 3 (5) | 0 | 0 | 0 | 1 (1) | 0 | 3 (8) | 0 | 1 (3) | 2 (4) | 0 | 0 |
| Heterocephalobus | 1 (3) | 0 | 0 | 0 | 1 (3) | 1 (2) | 1 (2) | 0 | 1 (2) | 0 | 1 (1) | 0 |
| Tylencholaimus | 1 (2) | 0 | 0 | 0 | 1 (2) | 0 | 0 | 0 | 4 (6) | 0 | 0 | 0 |
| Achromadora | 3 (8) | 0 | 1 (3) | 0 | 0 (1) | 1 (1) | 0 | 0 | 0 | 0 | 0 | 0 |
| Cephalobus | 0 | 0 | 0 | 0 (1) | 1 (3) | 0 | 0 | 0 | 1 (3) | 2 (4) | 0 | 1 (1) |
| Monhysteridae | 2 (3) | 0 | 0 | 0 | 1 (2) | 0 | 0 | 0 | 1 (3) | 0 (1) | 0 | 0 |
| Diphtherophora | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 4 (10) | 0 | 0 |
| Diplogasteridae | 1 (2) | 1 (3) | 0 | 1 (2) | 0 (1) | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Tylenchus | 0 | 0 | 1 (3) | 0 | 2 (3) | 0 | 0 | 0 | 0 (1) | 0 | 0 | 0 |
| Pungentus | 0 (1) | 0 | 0 | 0 | 1 (2) | 0 | 2 (5) | 0 | 0 | 0 | 0 | 0 |
| Nygolaimus | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 (1) | 2 (5) | 0 | 0 |
| Acrobeles | 0 | 2 (4) | 0 | 0 | 1 (2) | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Rhabdolaimus | 0 | 0 | 1 (3) | 0 | 0 | 0 | 0 | 0 | 0 (1) | 0 | 0 | 0 |
| Aporcelaimellus | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 (2) | 0 | 0 |
| Cylindrolaimus | 0 (1) | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Leptonchidae | 0 (1) | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Eucephalobus | 0 (1) | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Chiloplacus | 0 (1) | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Ecumenicus | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 (1) | 0 | 0 | 0 |
| Anguinidae | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 (1) | 0 | 0 | 0 |
| Trophic groups (nematodes/100 cm 3 soil) and community structure indices | ||||||||||||
| Bacterivorous | 138 (98) | 259 (214) | 179 (45) | 165 (123) | 133 (78) | 282 (452) | 165 (56) | 148 (94) | 128 (72) | 137 (69) | 112 (29) | 98 (47) |
| Fungivorous | 180 (60) | 262 (106) | 185 (43) | 193 (68) | 96 (61) | 186 (276) | 99 (48) | 171 (242) | 162 (66) | 204 (96) | 94 (37) | 89 (44) |
| Omni+Predsa | 8 (11) | 7 (12) | 5 (4) | 0 | 6 (6) | 10 (15) | 8 (9) | 3 (8) | 12 (8) | 17 (28) | 2 (2) | 1 (2) |
| Enrichment Index | 51 (9) | 51 (10) | 55 (12) | 53 (10) | 67 (12) | 52 (11) | 46 (15) | 53 (8) | 56 (10) | 46 (4) | 45 (12) | 46 (11) |
| Structure Index | 41 (10) | 25 (15) | 23 (12) | 12 (11) | 54 (19) | 32 (14) | 29 (11) | 17 (13) | 52 (13) | 46 (10) | 21 (14) | 13 (13) |
| Channel Index | 66 (19) | 61 (27) | 50 (21) | 60 (24) | 30 (17) | 50 (21) | 54 (21) | 51 (31) | 56 (19) | 70 (18) | 58 (12) | 64 (25) |
| Shannon Diversity | 7.30 (1.11) | 5.66 (1.65) | 5.97 (0.88) | 4.66 (1.15) | 6.79 (1.15) | 6.46 (1.22) | 4.94 (1.25) | 3.99 (0.80) | 7.51 (1.92) | 7.33 (2.48) | 5.37 (1.09) | 4.67 (1.01) |
| Simpson Diversity | 5.51 (1.04) | 4.60 (1.58) | 4.72 (0.70) | 3.82 (0.98) | 5.42 (1.00) | 5.12 (1.10) | 3.91 (1.07) | 3.17 (0.73) | 5.78 (1.79) | 4.69 (1.80) | 4.24 (1.02) | 3.69 (0.84) |
Table 2.
Effects of nitrogen fertilizer treatments on the Shannon–Weiner (S–W) and Simpson (Simpson) indices of genus-level diversity, the nematode Structure Index (SI) and Enrichment Index (EI), and population densities (nematodes/100 cm3) of omnivorous+predacious (O + P), bacterivorous (Bact) and fungivorous (Fung) trophic groups.
| Treatment | S–W | Simpson | SI | EI | CI | O + P | Bact | Fung |
|---|---|---|---|---|---|---|---|---|
| 0N | 7.02aa | 5.57a | 49a | 58a | 51 | 9ab | 133 | 146 |
| 1N | 6.48a | 4.90ab | 35b | 49b | 60 | 11a | 226 | 218 |
| 1.5N | 5.43b | 4.36b | 24c | 49b | 54 | 5bc | 152 | 126 |
| 2N | 4.44c | 3.51c | 14d | 50b | 58 | 1c | 137 | 151 |
| ANOVA summary (p-values) b | ||||||||
| Treatment | < 0.001 | < 0.001 | < 0.001 | 0.004 | 0.39 | 0.004 | 0.18 | 0.09 |
| Date | 0.21 | 0.57 | 0.05 | 0.07 | 0.002 | 0.47 | 0.19 | 0.04 |
| T × D | 0.57 | 0.80 | 0.29 | 0.05 | 0.18 | 0.67 | 0.91 | 0.70 |
1 Notes: Data are means of three sample dates (April, June, September) and six replicate plots per treatment. aMeans within a column labeled with the same letter are not significantly different according to Duncan’s means separation calculated at p = 0.05. bMixed-model repeated measures analysis of variance.