Sowing window
Choosing when to sow field pea requires a compromise between being early enough to avoid end of season drought and late enough to avoid bad blackspot infection. Since other crops, such as wheat, lupins and canola, benefit much more from early sowing, field pea should be sown after these sowing crops is complete. It is unlikely then that field pea will be sown too early and the important question will be how late is it safe to sow field pea?
Data from Department of Agriculture and Food, Western Australia trials suggest that, while best results will be obtained sowing around the beginning of June, or perhaps a little earlier in low rainfall areas, sowing is safe until the end of June in most parts of the state. Sowing should cease earlier in low rainfall areas north of the Great Eastern Highway: where there is 100 millimetres (mm) or more of water stored in the soil, sowing can safely continue until 15 June, but should cease on 1 June if there is less. Stored soil water makes little difference south of the Great Eastern Highway.
| North | South | ||||
|---|---|---|---|---|---|
| Rainfall | Date window | Target date | Rainfall | Date window | Target date |
| Low | If <100 mm soil water : 7 May-1 June If >100 mm soil water: 7 May-15 June | 25 May | Low | 7 May-30 June Blackspot risk reduced if delayed to June | 4 June |
| Medium | 15 May - 30 June | 1 June | Medium | 15 May-30 June Blackspot risk reduced if delayed to June | 10 June |
| High | 15 May-30 June | 1 June | High | 30 May-30 June | 10 June |
Inoculation
Field pea, being a legume, has the capacity to derive its nitrogen requirements from the atmosphere but, in order to do this it must be inoculated with Rhizobium bacteria that will form nodules on the crop's roots. Field pea should be inoculated with Group E inoculum before sowing, irrespective of whether the paddock has grown field pea before.
This is because the field pea Rhizobium does not survive well in Western Australian soils. Field pea can also be inoculated with Group F inoculum, although remember that the Rhizobium strains in the two groups may not always be equally effective on peas. Achieving good nodulation is crucial to growing a good crop, so take care to inoculate properly. Slurry inoculation is the best way to ensure a well nodulated crop.
Sow seed within three days of inoculation, as the inoculum has only a limited life span on dry seed. Fungicide seed dressings will further reduce the life span of the inoculum so, as seed dressings have little value in preventing disease in WA; their use is not recommended.
Granular inoculum is now available and can be applied to the soil separately in much the same way as fertiliser. This provides increased flexibility at sowing as it removes the need to inoculate within three days of sowing and will make achieving good nodulation compatible with fungicide seed dressings, should these ever become worthwhile in WA.