inoculating legumes

Carol A. Miles (milesc@wsu.edu)
Tue, 25 Jun 1996 22:12:36 -0800

I am often asked if it is necessary to inoculate legumes (peas, beans,
soybeans, vetch, clover, etc.) every seeding when the soil has a history of
growing these crops and the crop has previously formed nodules.

I understand Rhizobium does not necessarily overwinter well and that there
are soil predators which feed on it. We are in a mild climate (soils
generally do not freeze although we do get a dusting of snow) and summer
day tempertures average in the 70's.

Is there a general rule of thumb, i.e., if the crop nodulated last year, no
need to inoculate this year. Or, if you have had the crop within the last
3 years and it nodulated, no need to inoculate this year. Or, inoculate
every year regardless of crop/nodule history. Or, to complicate things,
perhaps certain plant species need inoculum every year while others don't.

I look forward to some learned opinions.

Carol A. Miles, Ph.D.
Washington State University
Extension Agricultural Systems
360 NW North Street
Chehalis, WA 98532
PHONE 360-740-1295 FAX 360-740-2792
milesc@wsu.edu