Secondary biosolids were applied to 16- and 26-year-old Douglas-fir (Pseudotsuga
menziesii (Mirb.) Franco) plantations (SI50 = 27 m and 36 m, respectively) in the Southern Moist
Submaritime Coastal Western Hemlock biogeoclimatic subzone (CWHmsl), British Columbia, in
order to investigate the effects on soil chemical properties, tree nutrient status, stand growth and
yield, soil moisture availability and tree water status, tree photosynthesis, leaf area index and water
use efficiency. Comparisons were made between liquid biosolids (3% dw) and dewatered biosolids
(30% dw) rewatered with liquid biosolids (1:3, w/v), and between biosolids applications in spring,
summer and fall, between 0 (control), 750, 1000 and 1500 kg-N/ha biosolids treatments, and
between 225 kg-N/ha urea/arrurionium nitrate treatment and the biosolids treatments in order to
determine the appropriate biosolids type, application season and rate(s) for the study area. Soil and
foliar samples were taken, soil and tree water potential, photosynthesis and leaf area index, and
tree growth were measured over a three year period (1993-95) following treatment. Secondary
biosolids treatments significantly increased forest floor total N, NH₄⁺-N, NO₃⁻-N, total available N
(NH₄⁺-N + NO₃⁻-N), and extractable P, but significantly reduced forest floor C/N ratio in the first
and second year after application. The N and P variables were also increased in the mineral soil,
but to a lesser extent. pH, electric conductivity, and exchangeable K, Ca and Mg were generally
unaffected by the biosolids application. Current year foliar N and S concentrations were
significantly increased, while foliar S0₄-S was significantly decreased by the biosolids treatments,
and the increase or reduction was correlated to the dose of applied biosolids. The biosolids effects
on foliar P, K, Ca and Mg were not significant. The secondary biosolids treatments also greatly
increased foliar nutrient ratios between N and other nutrients, and foliar Cu, Zn and Fe
concentrations. Application of secondary biosolids significantly increased current year foliage,
shoot and bud growth, current annual increments of DBH, height, and stand basal area,
irrespective of biosolids application season, especially in the second year following treatment.
There were no significant differences in the responses of soil chemistry, tree nutrition and growth
between the 3% solids biosolids treatment and the dewatered/rewatered (with 3% biosolids)
biosolids treatment. The spring biosolids application resulted in largest increases in soil N
availability, foliar N concentration and growth in comparison with the summer and fall applications. Both 1000 and 1500 kg-N/ha biosolids treatments significantly increased soil N and P
availability and foliar N concentration, but the former resulted in greater increases in tree growth
than the latter; the 750 kg-N/ha treatment also increased tree growth, but to a lesser extent. The
225 kg-N/ha fertilizer treatment had a similar effect on soil N availability, tree N nutrition and
growth, compared to the 750 kg-N/ha biosolids treatment, but it had little effect on total N,
extractable P, and C/N ratio in the forest floor and mineral soil. The biosolids treatment increased
soil water potential in the pot trial without seedlings, but there was no significant difference
between biosolids treatments and control in the field trial with trees. Tree twig xylem water
potential was significantly increased by the 1000 and 1500 kg-N/ha biosolids treatments during dry
summertime, irrespective of biosolids application season. The secondary biosolids treatments
significantly increased tree net photosynthetic rate, irrespective of stand age. Instantaneous water
use efficiency and a measure of leaf area index were also increased in the biosolids-amended
stands. The results in this study demonstrate that secondary biosolids fertilization significantly
improved soil N and P availability, tree nutrition and growth, increased soil water storage, leaf
area and photosynthetic efficiency, and reduced tree water stress, and that dewatered biosolids
rewatered with 3% biosolids (1:3, v/v), spring, and 750-1000 kg-N/ha are considered to be the
most appropriate biosolids type, application season and rate(s), respectively, in the study area.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/8662 |
| Date | 05 1900 |
| Creators | Zhong, Anliang |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Relation | UBC Retrospective Theses Digitization Project [http://www.library.ubc.ca/archives/retro_theses/] |
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