Nodulation and Nitrogen Use in Dry Beans
In late June, adzuki beans that had been in the ground for 3 weeks already had a few nodules on the roots (Figure 1), and the nodules were active (pink inside when split open). Another field of adzuki planted in the same region around the same time did not have any nodules on the roots, and neither did local black beans at a similar growth stage. Inoculants were not used on any of the fields. One key difference is that the adzuki beans with nodules had not yet received any nitrogen fertilizer. This scenario raises questions about nitrogen use in dry beans, given they are legumes that can convert atmospheric nitrogen into ammonium in the soil.
Figure 1. Adzuki beans with nodules (shown with red arrows) on June 25, 2024.
Why do some dry bean fields nodulate earlier, or nodulate more?
Nodulation begins about 14 days after bean emergence but could take 3 or 4 weeks depending on conditions. Nodulation generally reaches its maximum during early to mid-flowering. Phosphorous is required for rhizobia to form nodules and fix nitrogen, and phosphorous deficiency can limit fixation. Potassium and sulphur also play a role, as do soil moisture and other abiotic stresses.
In a study conducted by Dr. Peter Pauls and his research team at University of Guelph, addition of nitrogen fertilizer delayed nodulation, which is a well-documented response. It takes less energy to use soil available nitrogen than to fix atmospheric nitrogen. In the study Pauls applied 90 pounds of nitrogen per acre and it delayed flowering and maturity but it increased yield.
Would use of inoculants improve nitrogen fixation and decrease the need for fertilizer?
Inoculants for dry beans are not widely available in Ontario and are not being used. Studies conducted by Dr. Peter Pauls have shown that inoculation had little to no effect on yield and amount of nitrogen fixation, which agrees with numerous other studies. Plants genetics have a strong influence on yield and ability to fix nitrogen.
Nodulation of dry beans can occur with numerous different species of rhizobia. The bean variety being grown also influences if, or how well, the rhizobia species functions. Where nodulation is occurring without inoculants, there must be native species associating with plant roots.
How much nitrogen is recommended for dry beans?
Dry beans are widely described as poor nitrogen fixers. Many pulses are grown in Saskatchewan, and their ministry of agriculture ranks their pulses in ability to fix nitrogen as follows: faba bean > pea > chickling vetch > chickpea > lentil > soybean > lupin> dry bean.
In an Ontario study, Dr. Peter Pauls grew 23 heirloom and 19 conventional dry bean (Phaseolus vulgaris) varieties in soils with low nitrogen levels. Between 21 and 76% of the nitrogen in the harvested beans was derived from atmospheric nitrogen. If beans cannot fix all the nitrogen they need, there is value in applying nitrogen to crop. Adzuki bean (Vigna angularis) are a different species than the other dry beans (Phaseolus vulgaris) grown in Ontario. Oregon State University research estimates adzuki can only obtain half their required nitrogen through fixation.
At the Huron Research Station, Chris Gillard found that only cranberry bean yields responded positively to added nitrogen, while white and kidney did not. Alberta Pulse Growers recommend about 100 pounds of nitrogen per acre, while 30 years of research in North Dakota indicate about 40 pounds of nitrogen per acre should be applied to inoculated fields and 70 pounds per acre to uninoculated fields minus the soil test nitrate and N credit from the previous crop. Trials conducted in 2019 to 2020 by Michigan State University (MSU) on black, white and small red beans resulted in no significant difference in yield at rates ranging from 0 to 150 pounds of nitrogen per acre, but plant biomass and white mould increased with higher rates of nitrogen. Nitrogen rates above 30 pounds per acre also resulted in fewer nodules on plant roots. However, MSU still recommend applying 40 to 60 pounds of nitrogen per acre.
In recent years, Manitoba Pulse and Soybean Growers (MPSG) have been conducting extensive fertility trials at research stations, as well as on farms, to develop improved recommendations. Their observation from small plot research is that maximum dry bean yield was achieved at the lowest rate of applied nitrogen (35 pounds per acre) and in on-farm trials yield has not been increased by any nitrogen rate tested so far. MPSG guidelines state that producers can expect 86-93% of maximum yield without nitrogen or inoculant applied, and that if producers feel zero nitrogen is too risky, they should apply 35 pounds per acre.
In Ontario, most dry bean producers apply between 40 and 70 pounds of actual nitrogen per acre at planting. In a survey conducted by Ontario Bean Growers in 2021, completed by 55 producers, the majority said they apply liquid or dry nitrogen ahead of planting while about 25% said they apply nitrogen in a 2×2 band at seeding time. A small percentage of respondents apply nitrogen sometime during the growing season.
Weather Summary: Thursday June 27 to Wednesday July 3, 2024
| Location | Highest Temp (°C) | Lowest Temp (°C) | Rain for Week (mm) | Rain Since April 1st (mm) | GDD0C April 1st | GDD5C April 1st | CHU May 1st |
| HARROW | |||||||
| 2024 | 29.1 | 10.2 | 14.0 | 258.5 | 1543 | 1076 | 1462 |
| 2023 | 27.4 | 13.9 | 32.3 | 206.7 | 1339 | 885 | 1245 |
| 2022 | 31.1 | 9.2 | 0.9 | 208.9 | 1386 | 950 | 1383 |
| 10 YR Norm (11-20) | 27.7 | 16.6 | 18.6 | 291.9 | 1382 | 913 | 1385 |
| RIDGETOWN | |||||||
| 2024 | 30.1 | 7.4 | 25.7 | 339.8 | 1449 | 985 | 1370 |
| 2023 | 29.3 | 11.9 | 107.0 | 294.1 | 1268 | 822 | 1154 |
| 2022 | 31.2 | 6.6 | 2.4 | 176.4 | 1293 | 864 | 1265 |
| 10 YR Norm (11-20) | 27.9 | 14.4 | 11.8 | 240.2 | 1292 | 827 | 1285 |
| SARNIA | |||||||
| 2024 | 30.5 | 9.2 | 13.5 | 218.1 | 1428 | 967 | 1323 |
| 2023 | 30.2 | 12.3 | 16.0 | 188.2 | 1222 | 778 | 1072 |
| 2022 | 31.7 | 8.5 | 1.4 | 157.1 | 1268 | 845 | 1201 |
| 10 YR Norm (11-20) | 27.6 | 14.4 | 9.6 | 266.3 | 1244 | 782 | 1220 |
| LONDON | |||||||
| 2024 | 29.0 | 8.4 | 29.8 | 301.4 | 1424 | 959 | 1353 |
| 2023 | 29.0 | 8.1 | 35.7 | 275.6 | 1267 | 823 | 1160 |
| 2022 | 29.8 | 6.6 | 8.6 | 187.5 | 1247 | 827 | 1221 |
| 10 YR Norm (11-20) | 27.7 | 14.0 | 10.6 | 267.4 | 1269 | 808 | 1264 |
| BRANTFORD | |||||||
| 2024 | 29.2 | 8.7 | 18.7 | 244.6 | 1367 | 907 | 1305 |
| 2023 | 29.7 | 9.4 | 67.8 | 250.4 | 1257 | 811 | 1155 |
| 2022 | 31.4 | 7.4 | 4.2 | 179.2 | 1249 | 818 | 1188 |
| WELLAND | |||||||
| 2024 | 28.8 | 10.2 | 28.4 | 307.0 | 1424 | 959 | 1370 |
| 2023 | 27.7 | 10.7 | 78.6 | 244.1 | 1256 | 804 | 1137 |
| 2022 | 29.3 | 10.7 | 1.2 | 190.6 | 1292 | 853 | 1260 |
| 10 YR Norm (11-20) | 27.7 | 15.3 | 12.0 | 271.6 | 1271 | 809 | 1263 |
| GODERICH | |||||||
| 2024 | 26.2 | 6.6 | 2.7 | 200.6 | 1277 | 820 | 1186 |
| 2023 | 26.6 | 7.0 | 6.7 | 139.2 | 1146 | 718 | 1020 |
| 2022 | 30.3 | 7.4 | 7.5 | 147.6 | 1161 | 743 | 1100 |
| 10 YR Norm (11-20) | 25.5 | 12.6 | 7.2 | 231.4 | 1133 | 682 | 1104 |
| ELORA | |||||||
| 2024 | 27.1 | 8.2 | 7.7 | 259.7 | 1272 | 820 | 1217 |
| 2023 | 27.5 | 7.4 | 18.1 | 174.3 | 1160 | 730 | 1060 |
| 2022 | 28.9 | 7.0 | 3.7 | 166.5 | 1143 | 724 | 1085 |
| 10 YR Norm (11-20) | 26.3 | 11.6 | 17.8 | 266.8 | 1127 | 679 | 1111 |
| MOUNT FOREST | |||||||
| 2024 | 26.7 | 8.0 | 5.1 | 243.1 | 1257 | 807 | 1200 |
| 2023 | 27.7 | 7.6 | 1.6 | 223.7 | 1158 | 732 | 1056 |
| 2022 | 29.5 | 7.1 | 8.4 | 187.2 | 1143 | 731 | 1099 |
| 10 YR Norm (11-20) | 26.3 | 11.7 | 9.4 | 262.4 | 1110 | 670 | 1104 |
| BARRIE | |||||||
| 2024 | 27.4 | 7.0 | 8.8 | 389.3 | 1214 | 763 | 1170 |
| 2023 | 27.6 | 8.6 | 17.0 | 257.6 | 1137 | 705 | 1037 |
| 2022 | 27.0 | 7.9 | 3.3 | 209.2 | 1120 | 699 | 1081 |
| 10 YR Norm (11-20) | 26.7 | 12.7 | 7.7 | 248.3 | 1089 | 650 | 1079 |
| PETERBOROUGH | |||||||
| 2024 | 27.8 | 5.6 | 19.7 | 294.4 | 1245 | 791 | 1184 |
| 2023 | 28.4 | 8.5 | 9.5 | 192.8 | 1168 | 727 | 1041 |
| 2022 | 27.6 | 6.7 | 0.6 | 211.9 | 1153 | 721 | 1113 |
| 10 YR Norm (11-20) | 27.7 | 12.2 | 11.1 | 249.6 | 1143 | 694 | 1119 |
| KEMPTVILLE | |||||||
| 2024 | 28.3 | 6.2 | 16.2 | 304.7 | 1314 | 861 | 1284 |
| 2023 | 29.5 | 13.4 | 1.9 | 231.1 | 1233 | 797 | 1107 |
| 2022 | 27.7 | 10.9 | 5.2 | 303.6 | 1240 | 790 | 1203 |
| 10 YR Norm (11-20) | 28.9 | 14.1 | 24.1 | 262.0 | 1200 | 752 | 1193 |
| SUDBURY | |||||||
| 2024 | 25.7 | 8.2 | 31.5 | 358.5 | 1103 | 675 | 1078 |
| 2023 | 30.6 | 7.3 | 22.3 | 300.2 | 1065 | 672 | 1003 |
| 2022 | 23.8 | 8.0 | 6.2 | 195.0 | 1015 | 623 | 1016 |
| 10 YR Norm (11-20) | 27.6 | 12.3 | 15.5 | 238.5 | 992 | 604 | 1022 |
| EARLTON | |||||||
| 2024 | 26.9 | 6.6 | 52.2 | 324.9 | 1095 | 674 | 1082 |
| 2023 | 31.8 | 5.4 | 9.5 | 199.7 | 1051 | 656 | 995 |
| 2022 | 25.1 | 6.6 | 11.3 | 190.6 | 1019 | 636 | 1037 |
| 10 YR Norm (11-20) | 26.6 | 11.3 | 13.0 | 215.1 | 915 | 549 | 952 |
| SAULT STE MARIE | |||||||
| 2024 | 21.6 | 7.1 | 60.4 | 352.2 | 1009 | 568 | 914 |
| 2023 | 26.3 | 7.3 | 19.6 | 186.9 | 1023 | 627 | 931 |
| 2022 | 21.1 | 6.3 | 25.7 | 236.8 | 850 | 460 | 765 |
| 10 YR Norm (11-20) | 26.1 | 9.7 | 9.8 | 241.9 | 873 | 486 | 846 |
| THUNDER BAY | |||||||
| 2024 | 26.3 | 4.9 | 27.8 | 246.0 | 912 | 493 | 831 |
| 2023 | 28.3 | 9.2 | 19.5 | 176.4 | 925 | 553 | 913 |
| 2022 | 30.6 | 3.6 | 3.6 | 343.7 | 814 | 458 | 793 |
| 10 YR Norm (11-20) | 26.1 | 9.9 | 29.5 | 246.4 | 836 | 459 | 825 |
| FORT FRANCES | |||||||
| 2024 | 25.9 | 3.2 | 61.1 | 308.6 | 974 | 545 | 921 |
| 2023 | 29.7 | 10.5 | 18.8 | 154.3 | 1108 | 729 | 1142 |
| 2022 | 26.3 | 2.4 | 4.0 | 377.2 | 868 | 515 | 895 |
| 10 YR Norm (11-20) | 28.4 | 9.4 | 17.5 | 233.4 | 953 | 557 | 972 |