Belowground Dynamics of Intercropping Wheat with Pea in a Dryland Cropping System
Rieder, R. M. 2008. MSc. Thesis. Dept. of Environmental Sciences, Oregon State University, Corvallis, OR
Abstract
The Plant Root Simulator(PRS™)-probes (Western Ag Innovations Inc., Saskatoon, SK,
Canada) are an emerging tool for the study of in-situ nutrient supply rates. PRS™ -probes have
not been used extensively in Pacific Northwest dryland cropping systems. The objectives of this
study were to 1) evaluate soil nutrient supply rates for intercropping treatments and addition of N
fertilizer in relation to agronomic performance; 2) determine optimum sampling times for
observing differences in nutrient supply rates; and 3) compare nutrient supply rates in root
exclusion cylinders to supply rates adjacent to plant rows. PRS™ -probes were used within
established agronomic trials at Pendleton, OR, where N fertilizer and pea inter-seeding with
wheat were the treatments. Differences in nutrient supply rates were observed in connection with
N fertilizer application. Few or no differences were observed for intercropping treatments.
PRS™ -probes identified an increase in N supply associated with the observed grain yield
response to N fertilizer. Also, PRS™ -probes did not detect a difference in N supply for
intercropping where no grain yield response was observed. For most nutrients, the supply rates
were greater earlier in the measurement period (April), associated with higher soil moisture.
Most nutrient supply rates were not affected by the PRS™ -probe placements (in-row or within
root exclusion cylinders) during this period. PRS™ nutrient supply measurements were related
to plant response to N fertilizer and intercropping treatments in a one-year field experiment.
Most relevant nutrient data were obtained during April. PRS™ -probe placements inside a root
exclusion cylinder did not appear to be essential for nutrient measurements in this dryland
cropping system.
