NEW TOOLS AND METHODOLOGIES FOR IN SITU MONITORING OF ROOT ZONE SALINITY AND LEACHING EFFICIENCY UNDER DRIP AND SPRINKLER IRRIGATION

The objective of the present investigation has been to combine tracer principles and a hydrolytic microbial activity assay using fluorescein diacetate to monitor changes in microbial biomass within subsurface flow wetland mesocosms. The mesocosm hydrolytic activity was referenced to activated sludge concentrations treating a typical domestic wastewater at full scale. Microbial biomass activity levels within four laboratory wetland mesocosms treating a synthetic domestic wastewater were routinely monitored over a 21-week period of plant growth and rhizosphere development. Although above ground plant mass and tracer dispersion numbers suggested progressive root zone development, plant growth did not result in any measurable enhancement in microbial activity when compared to a mesocosm operating without plants. Dispersion numbers also suggested a reduction in the mass transport kinetics in these planted mesocosms. In-situ biomass monitoring enabled the assessment of a characteristic response in terms of the steady-state food to microorganism (F/M) ratio that was observed in mesocosms receiving both low and high organic loading. Wetland treatment performance is sensitive to the degree to which bed volume is exploited in terms of wastewater flow to regions of bioactivity. The in-situ reactive tracer technique for mesocosm biomass monitoring provided an assessment of the collective substratum and rhizosphere microbial biomass in direct contact with wastewater contaminants. Thus, in-situ biomass monitoring has application in further understanding of plant function and strategies for plant implementation in wetland research and development.

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SaltMod estimation of root-zone salinity Varadarajan and Purandara Application of SaltMod to estimate root-zone salinity in a command area

Materials and Geoenvironment ◽

10.2478/rmzmag-2018-0008 ◽

2018 ◽

Vol 65 (2) ◽

pp. 79-88

Author(s):

N. Varadarajan ◽

B.K. Purandara

Keyword(s):

Root Zone ◽

Drainage System ◽

Steady Increase ◽

Command Area ◽

Water Projects ◽

Salinity Levels ◽

Left And Right ◽

The Common ◽

Leaching Efficiency ◽

Root Zone Salinity

Abstract Waterlogging and salinity are the common features associated with many of the irrigation commands of surface water projects. This study aims to estimate the root zone salinity of the left and right bank canal commands of Ghataprabha irrigation command, Karnataka, India. The hydro-salinity model SaltMod was applied to selected agriculture plots at Gokak, Mudhol, Biligi and Bagalkot taluks for the prediction of root-zone salinity and leaching efficiency. The model simulated the soil-profile salinity for 20 years with and without subsurface drainage. The salinity level shows a decline with an increase of leaching efficiency. The leaching efficiency of 0.2 shows the best match with the actual efficiency under adequate drainage conditions. The model shows a steady increase, reaching the levels up to 8.0 decisiemens/metre (dS/m) to 10.6 dS/m at the end of the 20-year period under no drainage. If suitable drainage system is not provided, the area will further get salinised, thus making the land uncultivable. We conclude from the present study that it is necessary to provide proper drainage facilities to control the salinity levels in the study area.

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Survival and growth of the tree species and provenances in response to salinity on a discharge site

Australian Journal of Experimental Agriculture ◽

10.1071/ea02192 ◽

2003 ◽

Vol 43 (11) ◽

pp. 1293 ◽

Cited By ~ 13

Author(s):

N. E. Marcar ◽

D. F. Crawford ◽

A. K. M. A. Hossain ◽

A. T. Nicholson

Keyword(s):

Soil Salinity ◽

Tree Species ◽

Root Zone ◽

Salinity Gradient ◽

Eucalyptus Camaldulensis ◽

South Wales ◽

Discharge Site ◽

Survival And Growth ◽

Root Zone Salinity

The survival and growth of 24 native tree species planted in 2 trials on a saline discharge site, which had a soil salinity gradient as well as watertable depth and salinity, near Wellington in central-west New South Wales were investigated. Several provenances of some species (including Acacia stenophylla, Eucalyptus camaldulensis and E. spathulata) and clones of E. camaldulensis and E. spathulata, were also evaluated. Each accession was represented by a 5-tree row plot with 8 replications. Root-zone salinity (ECe 0–60 cm) at the tree and plot level was calculated from in situ measurements of bulk soil salinity using an EM-38 device (Geonics, Canada). Growth measurements are reported at 72 (trial 1) and 61 months (trial 2) after planting. For each trial, 4 replicates were classified as either non-saline (mean ECe <2 dS/m) or saline (ECe range from about 6 to 10 dS/m). Watertable depths varied from 0 to 1.5 m (depending on season) in the saline areas to >4 m in the non-saline, upslope areas. Survival and growth differed significantly between species, provenances and clones in both trials and under both saline and non-saline conditions. For most accessions, trees survived and grew better under non-saline conditions. Under non-saline conditions A. mearnsii, E. camaldulensis and E. occidentalis performed best; for example, A.�mearnsii (16268) attained a mean height of 7 m and mean DBH of 11 cm at 61 months in trial 2. Under saline conditions, A. stenophylla, E. camaldulensis, E. occidentalis and E. spathulata performed best; for example, E.�occidentalis attained a height of 6.9 m height and 12.3 cm DBH after 61 months in trial 2. Responses of selected species to root-zone salinity are provided; significant differences were found between species with E. occidentalis and A. stenophylla showing no growth decline up to ECe of 10 dS/m, while most other species showed varying rates of decline with increasing salinity. Three years after thinning each trial, good coppice regrowth was observed from cut stumps of all species except A. mearnsii and Melaleuca halmaturorum.

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