Sewage inputs were not measured directly at Sandy Lake; they were calculated from data collected for other lakes. Total phosphorus loading from internal sources such as sediments has not been estimated for Sandy Lake. The high phosphorus peaks recorded in both basins in September FIGURE 7 suggest that internal loading is substantial and would account for a large part of the total phosphorus loading to the surface waters.
The phytoplankton in Sandy Lake has not been studied intensively. One sample was taken from the south basin on 18 August by Alberta Environment Alta. The biomass of The most widespread emergent species were common cattail Typha latifolia , common bulrush Scirpus acutus and common great bulrush Scirpus validus , which were particularly dense in the south basin. Other species frequently recorded were sedges Carex spp. Sweet flag Acorus calamus , giant bur-reed Sparganium eurycarpum and yellow water lily Nuphar variegatum were also identified.
Pondweeds Potamogeton spp. In addition to the six pondweed species identified, northern watermilfoil Myriophyllum ex-albescens , stonewort Chara sp.
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The zooplankton and benthic invertebrates in Sandy Lake have not been studied. Sandy Lake is managed for sport fishing. No catch data are available, but the fishery is most popular for northern pike in spring and yellow perch in winter. Fishing derbies for both species are held during winter. During the s, pearl dace were reported present, and in , a few walleye were caught in the deepest part of the lake. These walleye were likely a remnant population, as they have not been reported since , and there is little walleye spawning habitat available Watters The incident was a severe kill that affected both northern pike and yellow perch.
Test nets in May caught some pike but no perch Watters The extreme north end of Sandy Lake is rated very good to excellent for waterfowl production Alta. Nesting cover is plentiful and loafing areas are available. Great Blue Herons are also present. Waterfowl production at the far end of the north basin, although good, is limited by the overgrown nature of the shoreline and a lack of offshore emergent aquatic vegetation Ducks Unltd. The remainder of the north basin and all of the south basin have a relatively poor rating for waterfowl production.
Alberta Environment. Sandy Lake. Alberta Forestry, Lands and Wildlife. Fish Wild. Alberta Native Affairs.
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A guide to native communities in Alberta. Alberta Research Council. Geological map of Alberta. Sandy Lake: Background information and management philosophy. Sandy Lake: Management plan alternatives.
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Sandy Lake area structure plan. Lac Ste. Energy, Mines and Resources Canada. Environment Canada. Canadian climate normals, Vol. Supply Serv. Holmgren, E. Over place names of Alberta. Producer Prairie Books, Saskatoon. Mitchell, P. Evaluation of the "septic snooper" on Wabamun and Pigeon lakes. Trophic status of Sandy and Nakamun Lakes. Strong, W. Ecoregions of Alberta. Twardy, A. Soil survey and land suitability evaluation of the Sandy Lake-Nakamun Lake study area. Watters, D. Office, Edmonton. Toggle navigation. Alberta Lakes Sign in. T1 was the control plot. All the plots were mulched with rice straw and halved into 2 subplots.
One subplot was cultivated with Panicum repens , a perennial grass, and the other with Sesbania rostrata , an annual legume. Monitoring: The experiment started at the end of a rainy season and terminated at the middle of the next dry season. During this period, the surface soil 5 cm , the groundwater tables and the plants were monitored. To confirm and to supplement the results of the preliminary field experiment, a full-scale field experiment with the 4 plots, which were the same as those in the preliminary field experiment, was conducted near the site of the preliminary field experiment.
The stability tests demonstrated the following facts: 1 All the PVA formed stable aggregates from the 2 sandy soil samples. Size distribution of aggregates Yt soil. Accordingly, GH was selected for further study. These experiments revealed the following facts 1 P VA remarkably increased stability of the aggregates of both soil samples.
These results confirm P VA is promising for desalinizing the salt-affected sandy soil in Northeast Thailand by suppressing capillary rise of saline water and by promoting leaching of the salt contained in the soil without disruption of the aggregates against the osmotic pressure during the desalinization. The field experiment confirmed most of the results of the preliminary field experiment. In addition, the following further information was obtained:.
Figure 7 illustrates assumed roles of PVA in the salt-affected infertile sandy soil in Northeast Thailand: to promote the desalinization by generating stable aggregates and to timely supply nutrients from cow dung to the plants by suppressing too rapid microbial decomposition of the cow dung. On the basis of the present study, application of PVA mixed with cow dung in the beginning of the rainy season is recommended for ameliorating the salt-affected infertile sandy soil at the place with high groundwater table.
However, further studies are necessary for extending this recommendation to the farmers in Northeast Thailand. This is because the rate and time of the application of PVA and cow dung should vary according to nature of both the soil and the plant. In addition, the present study revealed the following new findings: 1 Decrease in EC in the middle to late dry season. These findings should be thoroughly examined to understand their underlying principles. This effort may contribute to the integration of 3 research fields of soil science soil physics, soil chemistry and soil microbiology.
Arunin, S. Characteristics and management of salt-affected soils in Northeast Thailand. Carr, C. Potential application of polyvinyl acetate and plyvinyl alcohol in the structure improvement of sodic soils. In: Moldenhauer W. Soil Science of America Inc. Publisher, Madison, USA. McGowan International Pty. Tung Kula Ronghai Salinity Study. Puengpan, N. Salt-affected soils in Northeast Thailand and Strategies of their Amelioration.
Subhasaram, T. Takai, Y. Coastal and Inland Salt-affected Soils in Thailand. Their Characteristics and Improvement. Quantin, C. Grunberger 2 ; N. Suvannang 3 and E. Bourdon 4. Most lowlands in Northeast Thailand are cultivated to rainfed rice. The main constraint for rice production is drought associated with sandy and acid soils that are also often saline.
Efficient water management and organic matter OM inputs are low-cost solutions used by farmers to limit salinity effects and to enhance the physico-chemical properties of paddy soils where yield is very low. Field monitoring was conducted during the rainy season to explore the interactions between land management i. Several parameters Eh, pH, EC were continuously measured inside and outside saline patches in two adjacent contrasting plots, differing in management high management i. Soil solution was regularly sampled at three depths and analysed for Mn and Fe.
High reducing conditions appeared after flooding in all sites, but were limited inside the saline patch without OM addition. Anoxic processes lead to the reduction of Fe- and Mn-oxides, especially when OM was added. Where OM was not incorporated, high salinity prevented the establishment of the reduction processes and pH stabilised around 4. Even under high reduction conditions, Fe concentrations in the soil solution were below commonly observed toxic values.
Moreover, amended plots had better rice production yield. Water management and availability of organic carbon, which maintain saturation and control the extent of the reduction, are processes of major importance for pH regulation and rice production. Moreover, these practices were able to counteract the toxic effects that occurred in salt-affected paddy fields.
Most lowlands in Northeastern Thailand are cultivated with rice, but among them, 8. Water rises to the surface by capillary action and evaporates, so salts accumulate at the soil surface and a saline crust can be observed during the dry season. Therefore, salinity drastically affects soil fertility and rice productivity, already affected by the acidity of these sandy soils.
Then, farmers focus their efforts on cultivating less affected soils, so the result is that the salt-affected soils become more damaged. However, in Isaan, efficient water management and organic matter addition or green manuring are low cost solutions used by farmers to supply nutrients to these poorly fertile soils. In paddy soils, incorporating rice straw or green manure can be an useful way of adding organic matter and thus increasing carbon storage and providing nitrogen, phosphorus, potassium and other nutrients to soils Vityakon et al.
However, a poorly controlled incorporation of OM can be responsible of the appearance of strong reducing conditions that may have adverse effects on rice cropping, as for instance the production of sulphide and the subsequent formation of black roots Gao et al. The addition of organic matter or the incorporation of crop residues increases the organic matter availability and thus the anaerobic bacterial activity. This can lead to a high transfer of electrons from organic matter to oxides, especially amorphous or poorly crystallised ones, leading to the reduction of both manganese and iron, and also to the establishment of strongly reducing conditions.
Solubilisation of these elements is a function redox conditions driven by bacterial activity, organic matter availability, soil moisture and thus agricultural management. Moreover, reduction processes control the pH and the ionic composition of the soil solution, both acting on soil fertility Ponnamperuma, Thus, Mn and Fe are key indicators for understanding the reduction processes and thus the biogeochemical functioning of rice paddy soils.
In order to quantify the impact of realistic low cost agricultural practices on the biogeochemical functioning of paddy fields in N. Thailand, we have studied the interactions between agricultural management i. Field measurements included pH, Eh, EC and major elements in the soil solution, with a particular focus on Fe dynamics. The field investigation was carried out in , from July to November. The first plot was characterized by organic matter addition buffalo, poultry and pig manure mixed with sawdust , of around kg plot -1 year -1 , corresponding to 2. The second one did not receive any particular treatment, i.
Saline patches were observed during the dry season inside each plot, and monitoring points were selected to reach the maximum contrast of salinity over a short distance i. In each plot, one monitoring point was located inside an area were the production of rice was affected by high salt contents soil conductivityobtained by EM38 higher than mS. Soils were sandy loam from the soil series Kula Ronghai Natraqualf , which predominates in salt affected zones of Northeast Thailand lowlands.
Main characteristics are summarised in Table 1. The composition of flooding water, groundwater and soil solution was monitored during the entire rainy season. Flooding water was sampled close to each monitoring point and groundwater in piezometers. The free soil solution was sampled every week or every two days, inside and outside the saline patches, at 10, 25 and 45 cm depth in polypropylene pierced boxes buried in soil, as described by Boivin et al.
These devices allowed the soil solution to enter by free drainage and the sampling was carried out under a N2 atmosphere. Eh was measured in situ during the entire cropping season, inside and outside the saline patches in the two plots, at 10 and 25 cm depth. In L25 plot, Eh was measured continuously every hour, whereas in L14, measurement was performed manually once a week. Flooding water did not vary in composition during the cropping period, except a slight increase in EC at the end of October, mainly due to increasing Na concentration Table 2.
The groundwater salinity was very high and the aquifer was not chemically homogenous Table 2. In the L25 plot, strong reducing conditions prevailed. At 25 cm depth, Eh also decreased quickly in L25S, reaching to mV before increasing and stabilising at around mV. Oxidation peaks occurred at different times, corresponding to rainfall events.
Eh rapidly increased to oxidised values when plots were drained in November. In all locations except in L14S, EC increased with depth. Outside the saline patches, EC remained almost constant with time with slight fluctuations, around 6. Electrical conductivity values and variations were larger inside the saline plots.
After transplanting, pH at 10 cm depth in L25NS increased from 5 to 6. At 45 cm depth, pH remained low at 4. At 25 and 45 cm depth, pH remained very low, around 4. In L14NS, pH increased from 4.
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At all other depths and also at 10 cm in L14S, pH remained constant around 4. The main cation in the soil solution was Na, ranging from mmol. Inside the saline patches, Na concentrations were significantly higher and more variable with time with most of the values ranging from to mmol. As for pH, Fe and Mn concentrations in the soil solution differed depending on the management practices and on the depth. Fe solubilisation was significantly higher in L25 than in L14 Figure 2 , particularly outside the saline patch.
Fe reduction increased with rice growth and Fe concentrations reached 2. At 45 cm depth, Fe solubilisation was also high in L25NS, with the same trend as at the other depths, while it remained low in L25S, less than 0. After 55 days, Fe concentrations decreased dramatically until the rice harvesting. In L14, Fe reduction was low Fe concentration 0 to around 1 mmol. Figure 1. Changes in soil solution pH at 10, 25 and 45 cm depth, in the four monitoring points.
As a plant extracts water from the soil, the amount of PAW remaining in the soil decreases. The amount of PAW removed since the last irrigation or rainfall is the depletion volume. Irrigation scheduling decisions are often based on the assumption that crop yield or quality will not be reduced as long as the amount of water used by the crop does not exceed the allowable depletion volume.
The allowable depletion of PAW depends on the soil and the crop. For example, consider corn growing in a sandy loam soil three days after a soaking rain.
Even though enough PAW may be available for good plant growth, the plant may wilt during the day when potential evapotranspiration PET is high. Evapotranspiration is the process by which water is lost from the soil to the atmosphere by evaporation from the soil surface and by the transpiration process of plants growing in the soil. Potential evapotranspiration is the maximum amount of water that could be lost through this process under a given set of atmospheric conditions, assuming that the crop covers the entire soil surface and that the amount of water present in the soil does not limit the process.
Potential evapotranspiration is controlled by atmospheric conditions and is higher during the day. Plants must extract water from the soil that is next to the roots. As the zone around the root begins to dry, water must move through the soil toward the root Figure 7. Daytime wilting occurs because PET is high and the plant takes up water faster than the water can be replaced.
At night when PET decreases to near zero, water steadily moves from the wetter soil to the drier zone around the roots.
The plant recovers turgor and wilting ceases Figure 8. This process of wilting during the day and recovering at night is referred to as temporary wilting. Proper irrigation scheduling reduces the length of time a crop is temporarily wilted. Most crops will recover overnight from temporary wilting if less than 50 percent of the PAW has been depleted.
Therefore, the allowable depletion volume generally recommended in North Carolina is 50 percent Figure 9. However, the recommended volume may range from 40 percent or less in sandy soils to greater than 60 percent in clayey soils. The allowable depletion is also dependent on the type of crop, its stage of development, and its sensitivity to drought stress. For example, the allowable depletion recommended for some drought-sensitive crops vegetable crops in particular is only 20 percent during critical stages of development. The allowable depletion may approach 70 percent during noncritical periods for drought-tolerant crops such as soybeans or cotton.
Figure 7. As the plant extracts water, the soil immediately adjacent to the roots light areas dries. If the rate of water movement from moist zones is less than the PET, the plant temporarily wilts. Figure 8. At night when the PET is low, the plant recovers from wilting as water moves from moist zones dark areas to eliminate the dry zones around the roots.
Figure 9. The relationship between water distribution in the soil and the concept of irrigation scheduling when 50 percent of the PAW has been depleted. Three plant factors must be considered in developing a sound irrigation schedule: the crop's effective root depth, its moisture use rate, and its sensitivity to drought stress that is, the amount that crop yield or quality is reduced by drought stress. Rooting depth is the depth of the soil reservoir that the plant can reach to get PAW.
Crop roots do not extract water uniformly from the entire root zone. Thus,the effective root depth is that portion of the root zone where the crop extracts the majority of its water. Effective root depth is determined by both crop and soil properties. Plant Influence on Effective Root Depth. Different species of plants have different potential rooting depths. The potential rooting depth is the maximum rooting depth of a crop when grown in a moist soil with no barriers or restrictions that inhibit root elongation.
Potential rooting depths of most agricultural crops important in North Carolina range from about 2 to 5 feet. For example, the potential rooting depth of corn is about 4 feet. Water uptake by a specific crop is closely related to its root distribution in the soil. About 70 percent of a plant's roots are found in the upper half of the crop's maximum rooting depth. Deeper roots can extract moisture to keep the plant alive, but they do not extract sufficient water to maintain optimum growth.
When adequate moisture is present, water uptake by the crop is about the same as its root distribution. Thus, about 70 percent of the water used by the crop comes from the upper half of the root zone Figure This zone is the effective root depth. Soil Influence on Effective Root Depth.
The maximum rooting depth of crops in North Carolina is usually less than their potential rooting depth and is restricted by soil chemical or physical barriers. North Carolina subsoils have a pH of about 4.
Liming practices rarely improve soil pH below the 2-foot depth. Shallow soils Carolina slate belt soils or soils with compacted tillage pans coastal plain soils are examples of soils with physical barriers that restrict root penetration below the plow depth usually less than 12 inches unless subsoiling is practiced. Thus, for example, while corn has a potential rooting depth of 4 feet, when grown under North Carolina conditions, its maximum rooting depth is about 2 feet.
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Maximum rooting depths for several crops under North Carolina conditions are given in Table 2. The effective root depth is the depth that should be used to compute the volume of PAW in the soil reservoir. The effective root depth for a mature root zone is estimated to be one-half the maximum rooting depth listed in Table 2. For example, under North Carolina conditions corn has a maximum rooting depth of 2 feet; thus, the maximum effective root depth is estimated to be 1 foot.
Effective root depth is further influenced by the stage of crop development. Effective root depths for most crops increases as top growth increases until the reproductive stage is reached. After this time, effective root depth remains fairly constant. Maximum rooting depth and effective rooting depth as a function of corn development are shown in Figure Figure