Peanut field observations in the Texas South Plains in 1999 ... iIndicated high variability in the numbers of active nodules on peanut plants inoculated with Rhizobium. Often nodules are not found when they are expected, and this lack of nodulation could be due to soil chemical factors such as high pH or soil environmental factors such early season high temperatures.

At research locations ...

We examined site-specific Rhizobium nodulation in conjunction with associated plant tissue, soil chemical, and peanut yield and grade attributes along half-mile transects in two Gaines County, Texas peanut fields.

Preliminary findings:
· Initial results highlight the lack of correlation between Rhizobium nodule number per plant versus yield and grade. The high variability among plant nodule numbers at each sampling point suggest that either a micro-environment may exist or that the Rhizobium inoculum was not applied properly.

· Further tests on 2000 data will examine the relation to plant and soil chemical factors. Results will help Texas peanut producers understand what soil chemical and environmental factors may contribute to poor Rhizobium nodulation, which in turn necessitates expensive N fertilizer to achieve profitable yields for peanut.

· This project began in 2000. Field observations were key to recognizing that the degree of Rhizobium nodulation of peanut in West Texas is inconsistent. It is not explained by soil type or pH, type of inoculant, or producer practices.

· An initial survey of Rhizobium nodule counts was insufficient to explain yield, suggesting that more site-specific characteristics influence nodulation. Field observations and experimental work are being used to reinforce the importance of proper Rhizobium inoculation.