The behavior of turfgrass grown on paper-sludge-amended soils was evaluated over 2 years. Two experiments were performed, one with deinked sludge and another with primary sludge. Four paper sludge, sand, and organic soil substrate mixtures with proportions ranging from 0% to 50% paper sludge were incorporated into existing soils. Two fertilization levels were applied in strip plots across sludge treatments and three turfgrasses of seeded Kentucky bluegrass (Poa pratensis L. `Georgetown'), Kentucky bluegrass sod, and an 80 Kentucky bluegrass: 20 perennial ryegrass (Lolium perenne L. `Prelude') seed mix were arranged within split plots. Effects of deinked and primary sludge experiments were similar. Supplemental N and, to a lesser degree, P and K fertilization with N at ≈4.5 to 5.5 t·ha–1, P at 1.18 to 1.26 t·ha–1, and K at 1.34 to 1.46 t·ha–1 improved ground cover, turf color, and stand quality. Despite differences in visual evaluations, leaf mineral nutrition was only slightly affected by fertilization treatments. Soil in nonfertilized plots was several times lower in N-NO3 when compared to fertilized plots, regardless of sludge rate. Soil in fertilized plots had higher concentrations of inorganic N regardless of sludge amendment. The soil C: N ratio was ≈13:1 in nonamended plots and more than 15:1 under the highest sludge rate. Deinked and primary paper sludges can be used effectively as soil amendments if turfgrass receives adequate supplemental N, P, and K.
J. Norrie and A. Gosselin
Jeffrey Norrie, Chantal J. Beauchamp, and André Gosselin
Residues and by-products resulting from papermaking and recycling are receiving increased attention as beneficial soil amendments. Our research examines de-inked and primary paper sludge as a principal constituent of several substrate mixtures used as soil amendments in landscape horticulture. Three factors will be examined in a strip-split-plot design with four replications: substrate mixture (with organic soil and sand), fertilizer level, and plant species. Several paper sludge–organic soil–sand mixtures (maximum 50% sludge) were compared to an organic soil–sand control. A 15-cm layer of each mixture was incorporated into existing soil to a depth of 30 cm. Species of Spiraea, Physpcarpus, and Thuja were grown in addition to Kentucky bluegrass (seed and sod) and ryegrass (seed). Growth, rooting, and plant nutrition (foliar analysis) were examined. Preliminary results indicate poor ground cover and N deficiency in plants grown in all unfertilized plots. For sod and seeded grasses, control plots were slightly more healthy than sludge-amended plots, which was likely due to a greater concentration of available N from the organic soil. The bush species exibited similar responses. We conclude that a base fertilization is needed to decrease the C: N ratio of these substrates to ≈20 to 30 for sustained plant growth regardless of sludge amendments. Toxicity effects were due to the presence of organic contaminants, heavy metals, or both.
A. Fierro, J. Norrie, A. Gosselin, and C.J. Beauchamp
Paper recycling generates large quantities of de-inking sludge, which is disposed of mainly by landfilling. More ecological disposal alternatives include land application and use as a container nursery medium. In this study, raw de-inking sludge was evaluated as a medium component supplemented with applications of four N fertilization regimes for the growth of three grass species (Festuca ovina duriuscula, Agropyron elongatum, Alopecurus pratensis), and four regimes of P fertilization for the growth of three Rhizobium-inoculated legumes (Medicago lupulina, Galega orientalis, Melillotus officinalis). Fertilizer was applied on the basis of sludge rate to maintain a uniform C: N ratio across sludge treatments. In one experiment, sand was mixed with 0, 10%, 20%, and 30% sludge by volume and 20% perlite, while in a second experiment, mineral soil was mixed with 0, 27%, 53%, and 80 % sludge and 20% perlite. Results indicate that shoot dry weight of all species increased with the amount of sludge in the mixture in tests with sand. In the soil mixture experiment, grasses showed the best response to treatments of 53% sludge mixture at the two highest N treatments. In general, shoot dry weight was more directly related to the total amount of N applied than to the C: N ratio of the substrate. The nutritional status (foliar N and P) also was investigated for one grass and one legume species.
J. Norrie, M.E.D. Graham, and A. Gosselin
The use of potential evapotranspiration (PET) estimates to identify irrigation timing for greenhouse tomatoes (Lycopersicon esculentum Mill.) grown in peat-based substrate was evaluated for a spring and fall crop. PET (using the Penman equation) was calculated from leaf, wet and dry bulb temperatures, and incident and reflected photosynthetic photon flux. Substrate matric potential (SMP) was monitored continuously using electronic tensiometers. Two irrigation starting setpoints (-4.5 and -6.5 kPa SMP) and two nutrient solution electrical conductivity (EC) treatments (1.5 and 3.0 dS·m-1) were factorially combined in a completely randomized design. Irrigation frequency was greater in treatments irrigated at -4.5 than at -6.5 kPa. The integral of calculated PET values was correlated with SMP for both experiments. Accumulated PET values were higher at the start of irrigation in the -6.5-kPa treatments for spring and fall crops. Nutrient solution EC did not influence irrigation frequency. Leaf pressure potential (LPP) was correlated to PET-predicted LPP (r 2 > 0.56) in plants subjected to high EC, low (-6.5 kPa) matric potential setpoint, or both treatments. PET and electronic tensiometer technology can be used jointly to improve irrigation management for tomatoes grown in peat-based substrates by more accurately responding to crop needs for water and nutrients.
J. Norrie, M.E.D. Graham, P.A. Dubé, and A. Gosselin
An automatic irrigation system was designed for use on green-house tomatoes growing in peat-based substrates. This system uses electronic tensiometers to monitor continuously substrate matric potential (SMP) in peat-bags. The system also uses the Penman equation to evaluate potential evapotranspiration (PET) through the acquisition of many greenhouse environmental parameters. Through a series of linear equations, estimates of PET are used in a computer-controller system to vary the electrical conductivity (EC) of irrigated nutrient solutions, as well as SMP setpoints at which irrigations are started. Such modifications to current irrigation management systems may improve fruit quality and reduce the risk of water stress during periods of high PET by irrigating more frequently with less-concentrated nutrient solutions. Conversely, during periods of low PET, irrigation is less frequent with more-concentrated nutrient solutions. Although no differences were found in fruit number or overall yield using variable nutrient solution EC, plant fresh weight was higher in those treatments. It is concluded that an integrated tensiometer-PET system may give increased precision to irrigation management and the control of crop growth in the greenhouse.