Last week within the Agri-Trend network we had another excellent conference call. The topic of the call was how to evaluate nodulation. We had our Senior Agri-Coach Tracey Preete lead share some great information. Checking nodulation consists of pulling a few plants, seeing how many nodules are present on the plants’ root system, and seeing how the plant is functioning. One thing we talked about was how to better evaluate nodulation and how to allow for some comparison between fields or from year to year.
Nodulation should be checked as early as two weeks after emergence in crops such as field peas, chickpeas, and lentils. Nodule numbers generally increase to a maximum in these crops at the mid-flowering stage. Checking the nodule number and function around three to four weeks after emergence will allow time for any corrective action that may take place if there are problems.
The best way to check nodulation is to dig up a group of plants (approximately four or five) should be dug up with the root mass and surrounding soil intact. Then, soak the plants in a pail of water and carefully remove the soil.
A few things that should be kept in mind when assessing the nodulation are as follows:
➢ The plant growth stage
➢ The sample location (avoid hilltops, low spots, herbicide overlaps, etc)
➢ Variety differences
➢ Soil test nitrate levels (may delay nodulation or nodule function)
➢ Starter fertilizer rates (may delay nodulation or nodule function)
➢ Field history that includes pulse crops (background of residual levels of Rhizobium)
➢ Inoculant type:
↳ Soil-applied inoculant products will result in nodules on both the primary and secondary
↳ Residual or background Rhizobium bacteria usually produce nodules on secondary roots away from the primary root and crown
Generally, low nodule numbers or poorly functioning nodules do not always mean that there are problems but it should cause you to investigate further. Detecting a problem early enough will give you time to take tissue samples, check soil test nitrate levels or other reasons for lack of nodulation to determine if corrective actions are needed. If you have any questions at all, please do not hesitate to contact your Agri-coach. We hope you’re all thrilled to be done with seeding and into spraying.