|Abstract or Summary
- The effect of incorporated sawdust, sawdust mulch and nitrogen (N) fertilizer rate on
soil nutrients and other properties, N uptake, and plant growth in a young blueberry
planting on a silt loam soil type was studied in 2004 and 2005. ‘Elliott’ highbush
blueberry plants were established on raised beds that were either constructed with the
incorporation of a fir sawdust amendment, or left un-incorporated. Plots were then
mulched with sawdust or left bare after planting. Nitrogen fertilizer, depleted 15N
ammonium sulfate, was applied at three rates, 22, 68, and 114 kg·ha-1 of N in the first
year, with non-labeled N fertilizer applied in the second year at the same rates. There
was a wider range in soil temperature in plots incorporated with sawdust and
mulched, from -2 ºC in winter to 41 ºC in summer, than in un-mulched plots.
Sawdust mulch did not appear to mitigate summer or winter soil temperatures.
Incorporated plots required 5-6 times more irrigation water than non-incorporated
plots during the growing season. Soil pH was reduced with higher rates of
application of fertilizer N, but incorporating sawdust or mulch minimized the
reduction in pH. Soil phosphorus concentration was reduced in incorporated plots.
The reduction in pH and incorporating sawdust significantly lowered soil P. Preplant
incorporation with sawdust increased soil organic matter by ~50% the first year.
Plant shoot and whip growth rate in both years was increased by mulching compared
to un-mulched plots. There was a significant incorporation by mulch interaction for
whip growth in 2004 and total dry weight and biomass partitioning in both years.
Whip growth rate on plants in un-incorporated, mulched plots was higher than in all
other treatments, peaking at 1.2 cm·d-1. Total plant dry weight was greatest in unincorporated,
mulched plots. Nitrogen fertilizer rate had no effect on total plant dry
weight or partitioning. Total N uptake was greatest in un-incorporated plots, but the
proportion of N derived from the fertilizer (NDFF) was highest in plants growing in
incorporated, un-mulched plots, up to 54% NDFF. Overall, plant growth was reduced
with the addition of pre-plant incorporated sawdust and no mulching in this soil type.