Research Summary:
How dryland wheat responds to biosolids fertilization at eleven field sites
D.M. Sullivan, A.I. Bary, C.G. Cogger, E.A. Myhre, T.E. Shearin and
T.N. Cramer
Oregon State and Washington State Universities
Results and Discussion
Figure legend: *, ** = Significant difference at 5 and 1 % probability levels,
respectively at a location.
Grain Yield
Three general response patterns were observed at the 11 field locations:
- Yield with biosolids (agronomic rate) = yield with fertilizer N
- No yield response to applied biosolids or fertilizer N
- Two locations: K-92 and L-92. These locations had higher pre-application soil nitrate-N
concentrations.
- Superior grain yield with biosolids compared to fertilizer N
- Three locations D-94, S-92, and Ore-96
- Superior yields with biosolids occurred in crop years with above-average precipitation
during critical periods (winter and late spring of crop year):
- Above-average crop year winter precipitation moved accumulated nitrate-N out of the soil
profile (Location S-92). After winter leaching, plots fertilized with inorganic N in
fallow were nitrogen deficient. With biosolids, additional available N was provided by
mineralization of biosolids organic N in the spring of the crop year.
- Above average crop yearspring precipitation (Locations D-94 and Ore-96) increased grain
yield potential and increased crop response to available N. Biosolids at an
"agronomic rate" generally provided more available N (60 to 120 kg/ha) than did
the inorganic N fertilizer treatment (50 to 80 kg/ha).
Figure legend: *, ** = Significant difference at 5 and 1 % probability levels,
respectively at a location.
- Test weight is a measure of grain plumpness. Low grain test weight reduces grain market
grade and grain price.
- In dryland wheat, excess N promotes lush vegetative growth (stems and leaves) and
sometimes lodging (plants fall over).
- Excess vegetative growth and lodging reduces water available for grain production.
- Shriveled (low test weight) grain is produced by water-stressed plants.
- Biosolids reduced test weight at four locations, indicating excess available N and
water-stressed growing conditions.
- Wheat varieties differ in their response to excess available N. The variety Eltan
was grown at 3 of 4 locations where biosolids reduced test weight. Eltan is a
taller wheat variety and is more susceptible to lodging than the varieties grown at other
locations.
Figure legend: *, ** = Significant difference at 5 and 1 % probability levels,
respectively at a location.
Grain Quality (Grain N--Protein)
- Low grain N (low protein) is desirable in soft-white wheat markets
- In our study, biosolids-fertilized grain had higher N concentrations at 7 locations.
- Across locations, average grain N concentration with biosolids was 19.7 g/kg vs. 16.5
g/kg with fertilizer N
- Currently, grain N is not a factor influencing grain price, but there may be premiums
for low protein grain in some markets in the future
- The higher grain N associated with biosolids fertilization could be an economic
advantage for different classes of wheat (e.g. hard white). Hard white wheat acreage is
increasing in the Northwest.
Figure legend: *, ** = Significant difference at 5 and 1 % probability levels,
respectively at a location.
- Post-harvest nitrate-N is an indicator of excessive available N supply.
- Biosolids = fertilizer N (9 locations)
- Biosolids > fertilizer N (2 locations)
