Chapter 13 Cold vertisols and their management

479 Chapter 13

COLD VERTISOLS AND THEIR MANAGEMENT A.R. MERMUT, D.D. PATTERSON and P.A. McDANIEL

13.1. INTRODUCTION

It has been long recognized that fine textured soils dominated by swelUng silicate clays differ from other Mollisols occurring in cold regions (Mitchell et al., 1944). Previously, these swelling clay soils occurring in the north central U.S.A. and the Canadian Prairies with cryic temperature regime and morphological characteristics similar to Vertisols were excluded from this order. According to Soil Survey Staff (1994) these soils are now classified within the new suborder Cryerts. Several research studies were initiated to examine the characteristics and behavior of the cold Vertisols in Saskatchewan, Canada (Mermut and St Arnaud, 1983; Mermut and Acton, 1985; Dasog et al., 1987). Clay soils occupy a significant area in western Canada and about 5.6 million ha of the soils are located in the southern Canadian prairies (Onofrei et al., 1990). The solum of Cryerts have cracks, slickensides, high clay contents with smectite, high coefficient of linear extensibihty (COLE) values which are common among the Vertisols. Currently Cryerts were subdivided into Humicryerts and Haplocryerts (Soil Survey Staff, 1994). The lack of knowledge about their detailed characteristics and geographic distribution in the world do not allow the establishment of realistic subdivisions of Cryerts. A new soil order "Vertisolic" is added to Canadian Soil Toxonomy to accommodate these soils in the system (Brierley et al., 1996). Clay soils with vertic properties are reported in Western Canada (British Columbia, Alberta, Saskatchewan and Manitoba) and several states in north central and northwestern U.S.A. (Minnesota, North and South Dakota, Montana, Idaho and Wyoming). They are expected to occur on lacustrine basins of northern Europe, including the Russian Steppes, and cold regions of central and central east Asia. Currently there is no major source of information that covers the characteristics and use and management of these cold Vertisols. The aim of this chapter is to put together a review on cold Vertisols using the recent information and available internal reports. More emphasis will be given to the use and management of these soils. 13.2. FORMATION AND DISTRIBUTION OF COLD VERTISOLS

The lack of information on the genesis of cold Vertisols does not permit us to write a more comprehensive chapter. The discussions presented here are based mainly on the recent studies of these soils in Canada.

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A.R. MERMUT, D.D. PATTERSON and P.A. McDANIEL

13.2.1. Parent material Detailed characterization of some swelling lacustrine parent materials from Saskatchewan (Mermut et al., 1984) confirmed that cold Vertisols are dominated by smectites and have similar clay mineral composition to other Vertisols. This suggests that the clays originate from the same source. It is generally assumed that Cretaceous shales, that extend from the Gulf of Mexico to Arctic Canada, are the major source of clays found in glacio-lacustrine deposits in the Canadian Prairies. Cold Vertisols in Minnesota, North and South Dakota, and Montana also inherited most of their properties directly from Cretaceous shales or shale derived parent materials, such as Boulder Lake series (Idaho, National Cooperative Soil Survey Internal Report). The general order of siUcate clay minerals which remains almost constant throughout the profile is: smectite > 50 percent, iUite 15-30 percent, kaolinite 10 percent, vermicuHte < 10 percent) in the coarse clay fraction. The soils with slickensides have clay content > 50 percent at the surface and this generally increases with depth. The clay fraction has up to 50 percent fine clay and have a high surface area (600-800 m^g~^), important factors when considering the swell-shrink potential of these soils (Dubbin et al., 1993; Mermut et al., 1984). Soils that have <50 percent smectite, >30 percent ilUte, or unusually high carbonates in the clay fraction may be qualified as intergrades to other soil orders, if they have one or two slickensides in their profiles. Clay soils in Quebec have almost no smectites and do not have the morphological characteristics, neither qualified for Vertisols nor for intergrades (Lamontagne and Cossette, 1994). 13.2.2. Climate The soils have evolved under sub-arid to sub-humid moisture and cool temperature regimes. Mean annual soil temperature at a depth of 50 cm is about 4-6.6°C (Dasog, 1986). Mean daily summer air temperatures are about 12.5-17°C, whereas mean daily winter temperatures are near — 15°C. Annual rainfall ranges between 200 and 400 mm. It is usually confined to early spring and sometimes late fall. The soils are characterized by seasonal moisture deficit and relatively long periods of drying to depths between 1 and 2 m (Mills et al., 1990), which result in the formation of cracks. The frost-free season ranges, generally, between 60 and 90 days, decreasing in length with increasing latitudes. The cold Vertisols that occur at high altitudes (>1700m) may have frost-free seasons as low as 60 days. These climatic conditions result in grassland and grassland-forest transition vegetation. 13.2.3.

Topography

The cold Vertisols are found generally on nearly level large lake basins. Good examples are the Lake Agassiz and Regina basins. The Lake Agassiz Basin slopes to the center at 0.5 m per 1 km, on both sides of the Red River. The area must have been quite wet at times prior to the installation of drainage canals. Excess water was a problem in this basin. In fact, a common comment among "old timers"

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in reference to road construction and ditching is that "we dig roads and build ditches". The soils on the nearly level lacustrine lake plain may show some kind of micro topography. Although there seems to be no gilgai, the presence of discontinuous horizons appearing as subsurface lenses, is the evidence of micro-highs and micro-lows and may represent a kind of gilgai micro topography. When such areas are cultivated to cereal crops, plant growth on depressions is expected to be better but may mature later. Thompson and Beckmann (1982) reported considerable difference between micro-high and micro-low in Australia, regarding the organic matter, N and micronutrient contents. Some soil may have undulating topography with slopes >15 percent. On steep slopes, due to erosion, soils are very shallow and do not have characteristic morphological features of Vertisols. Slumping may be observed in some sloping terrain. 13.2.4. Soil moisture behavior The cold Vertisols crack as a result of seasonal moisture fluctuation. The degree and frequency of changes in moisture content of the soil are likely the most important parameters that control the intensity of cracking and soil displacement and formation of slickensides. As in other Vertisols, most water is transmitted down through the cracks and macro-voids to the subsoil. Unfortunately there is no measurement of soil water distribution in a flat or nearly flat landscape to show differential wetting and drying. However, it is expected that there will be relative differences in moisture status with a rolling landscape. Some measurements by Bauer and Kucera (1978) made at Casselton (32 km west of Fargo) appears to be interesting. The soils at Casselton are of silty clay and clay textured class and somewhat poorly drained. In their report Bauer and Kucera (1978) discuss the influence of time and type of tillage systems and plant type on the moisture distribution in the profile. In this area, soil moisture increases from November to April in the subsoil. This seems to be interesting. If the soil had cracks in November, in early spring the melt water will directly wet the cracks through the so-called bypass flow and as a result the subsoil will receive more moisture. It is suggested that cold Vertisols should not be plowed in the fall. Bauer and Kucera (1978) confirmed that increase in available soil moisture content in the subsoil at both 30-60 cm and 60-90 cm depths on no-fall tillage were always larger than following moldboard plowing. The available soil moisture decreased below 90 cm. It is known that expansion and contraction of Vertisols are related to the amount of water added or removed during seasonal moisture changes, which are also fundamental for the formation of slickensides. Dasog et al. (1987) suggest more than one cycle of wetting and drying, once during the spring melt and once or twice during the summer. It is known that cracks promote bypass flow of water, which induces differential wetting in the subsoil. They suggest that such wetting occurs during the periods of heavy rain in the late summer or fall. In a year when fall precipitation is low, cracks may remain open

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A.R. MERMUT, D.D. PATTERSON and P.A. McDANIEL

Distribution of Cloy Soils

Fig. 13.1. Distribution of clayey soils in Canada (from Tarnocai et al., 1990).

during the winter. In such years, differential wetting occurs, due to bypass flow of melt water during which some surface fine granular aggregates are also transported, in addition to crack infill by gravity. 13.2.5. Distribution of cold Vertisols in the world According to Soil Survey Staff (1994), Vertisols that have a cryic soil temperature regime are classified within the newly established Cryert suborder. Based on limited data, a map is produced showing the distribution of clay soils in Canada (Fig. 13.1). This map needs to be improved as more information becomes available. Cryerts were observed in western Canada(southern part of Manitoba, Saskatchewan, Alberta, and British Columbia) and north central U.S.A. (North Dakota, South Dakota, Minnesota, Montana, Idaho, and Wyoming). As the clays in Ontario and Quebec contain very little or no smectites, the heavy clay soils in this part of Canada do not possess any characteristics related

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483

to Vertisols (Kodama et al., 1993; Lamontagne and Cossette, 1994). A^ stated earlier, the environmental conditions exist for Cryerts to occur in glacio-lacustrine basins of Europe (including the Russian steppes), high plateaus of central Asia (Kazakistan, Ozbekistan), and Manchuria (northeast China) with cryic temperature regime.

13.3. CHARACTERISTICS OF COLD VERTISOLS

No attempt is made here to fully characterize the cold Vertisols. Rather, a few examples are taken from the available literature to illustrate the state of the art and need to increase our knowledge in this area. 13.3.1. Physical properties Increasing clay content with depth, in general, is the typical characteristic of cold Vertisols in Saskatchewan (Dasog et al., 1987). Sand content is notably low. Cryerts contain >50 percent clay. They show increasing clod bulk density with depth, usually reaching a maximum in the lower part of the solum and then decreasing again with depth (Dasog et al., 1988; Table 13.1). The COLE values are high (>0.09). Plasticity index values are also high and most horizons are classified as plastic inorganic clays (HC), in the unified soil classification system used by engineers. As shown by Dasog et al. (1987), both COLE and plasticity index follow the trend in fine clay. Dasog et al. (1988) reported a high degree of correlation between fine clays and COLE, with r = 0.92 COLE = 0.042 + 0.037 (percent fine clay) Shrinkage curves of some Saskatchewan soils (Fig. 13.2) show that there is a shrinkage in the range of field moisture, therefore cracking is expected. As in the other Vertisols, all Cryerts exhibit cracking. Dasog (1986) showed that, in the subarid regions of Saskatchewan, the cracks were less intense in comparison with Vertisols in ustic and udic moisture regimes. Under native grassland, the cracks were significantly narrower and shallower than in the cultivated soils. The width and depth of cracks may be increased steadily through the summer. Cracks were more distinct below the surface horizon under native grasses. Precipitation during the summer, however, prevents the wider crack formation. In years when fall precipitation is low, the soil may enter the winter in a dry and cracked state. Ripley (1973) attributed rapid warming of a Sceptre soil in Saskatchewan to infiltration of snowmelt through cracks. Swelling pressures of 400-1000 kPa and shear strengths of 20-40 kPa was observed when Regina soil material was extensively moistened (Fredlund, 1975), clearly indicating that potential for shearing exists in these soils. It appears that slickensides may form in subsoils where the difference between horizontal and vertical stress is large and the upper solum lies in a relatively stable zone where low overburden pressure and cracks would prevent the development of high lateral

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Stress. The zone of slickensides extends below the depth of open cracks, suggesting that crack filling is only partly responsible for soil displacement and formation of shckensides. 13.3.2. Chemical properties The soils are mildly and moderately alkaline throughout the solum and parent material. In more humid regions, at the surface, pH may be moderately acid. At depth salinity may be observed. Organic C is lower and decreases gradually with depth. Carbonates are present in many soils throughout and weak accumulation of secondary carbonates in the subsoil may be observed (Table 13.1). Cation exchange capacity is generally above 30cmolckg~^. The narrow ratio of exchangeable Ca/Mg is attributed to higher Mg in the soil solution, either from dolomitic limestones and/or Mg replacement from layer silicates during pyrite oxidation, as proposed by Mermut and Arshad (1987). Magnesium may be the dominant exchangeable cations in some soils in Saskatchewan (Dasog et al., 1987) and clay soils with Solonetzic morphology in Manitoba (Ellis and Caldwell, 1935). Exchangeable Na is negligible in the upper solum, but exchangeable Na percentage (ESP) may be between 7 and 10 percent in the lower solum. Southern clays in Saskatchewan contain more than 15 percent exchangeable Na"^ and high amounts

COLD VERTISOLS AND THEIR MANAGEMENT

487

of electrolytes at depth and the amounts of exchangeable Na"^ and electrolytes decrease gradually towards the north (Mermut et al., 1990). 13.3.3. Fertility of cold Vertisols Clay soils (cold Vertisols and Vertic intergrades) in Saskatchewan are rated as excellent soils for wheat growing (Mitchell et al., 1944). Regina clays in the Dark Brown soil zone are considered the best wheat lands in the province. The Red River clay (usually an imperfectly drained soil with an artificial surface drainage network) and Dauphin clay are rated the most productive soils in Manitoba (Onofrei et al., 1990). The appHcation of P fertilizers is very beneficial. Early work in western Canada has shown the advantage of supplying N with P and this has led to the widespread use of monoammonium phosphate as P fertilizer sources. Studies show that as much as half of the soils original supply of organic matter and nutrients, including N, have been consumed within the last 80 years in the Indian Head heavy clay soils (Humicryert). The minimum level of N considered sufficient is 80-100 kg ha"^. As the organic matter continues to decline, the soils will Hkely require more N (Staff Saskatchewan Soil Survey, 1984). Many crops remove almost as much S as P from the soil. Canola, mustard, and forages containing a legume component have a higher sulfur requirement than cereal grains or flax. Up to 85 kg ha"^ S is used for canola, mustard and flax. Most Saskatchewan soils, especially heavy clay soils, contain adequate amounts of micronutrients. Wilding et al. (1990) indicate that soil fertility in Vertisols in general, especially in soils in which morphological variability is common, is not well understood and needs close attention, especially considering the application of water, chemicals, such as fertilizers, herbicides and pesticides. This applies to the cold Vertisols as well. Long-term fertiUty management studies on a Fargo clay, in North Dakota by Young et al. (1960) also showed a decline of both total N and organic matter contents. Additions of organic residues and manure were found effective in the long-term maintenance of these constituents. The C/N ratio for the Fargo soil is between 10 and 14, and it decreases slightly with increasing depth. Liming additions of organic residues and manures had no effect on the maintenance of total N or organic matter in this soil. The capacity of the Fargo soil to produce plant available N using the laboratory incubation and greenhouse techniques, correlated well with total N contents. Plots that received manure were capable of releasing more available N than residue plots of the same N content. Phosphorus-treated plots, in addition to manure and organic residues, lost slightly more total N and organic matter than those which received only the manure or residues. During the 40 years (1913-1953) of cropping, the crops grown on the P plots yielded shghtly more than those on non-phosphated plots, and hkely removed more N. It is possible that P increased microbial activity, thus, resulting in faster decomposition of the organic matter. Available P declined appreciably in check plots, and the loss in residue and

488

A.R. MERMUT, D.D. PATTERSON and P.A. McDANIEL

manure plots was not quite as great. Plots treated with 20 kg ha~^ (P) every fourth year contained more available P at the end than they did at the beginning of the experiment. The decUne of organic P was about 27 percent within the 40 years of the experiment and organic P content was found to be correlated with total N content. As also suggested by Young et al. (1960) for the Fargo soil, Cryerts are adequately supplied with exchangeable K. Following the 40-year experiment the check plots were shghtly depleted in exchangeable K. However, those plots that were treated with manure or organic residues had more exchangeable K. This study concludes that the important change in Fargo clay soil brought about by 40 years of cropping, He in the area of N and P fertility. The apphcation of manure and organic residues reduced the rate of loss somewhat and the manure used did not appear to be much superior to organic residues in maintenance of these constituents. The manure and organic residue plots had slightly better tilth than check plots. Studies in the interior plains of western Canada (Mitchell et al., 1944; Onofrei et al., 1990) show that the clay soils have higher fertility status and, therefore, higher potential for crop production than the other regional soils. Their resistance to droughts is also well known.

13.4. USES AND MANAGEMENT OF COLD VERTISOLS

In general, farm size and cropping systems in the Interior Plains of western Canada change with gradient in temperature and precipitation (Onofrei et al., 1990). While farm size and proportion of summer-fallow land decrease from the Brown to the Black soil zone (Fig. 13.3), however, there is a progressive increase in absolute value of land and crop production per hectare, with decreasing farm size. Therefore, in the Black soil zone total capital investment and operating expenses are the highest. Overall, farms on clay soils out-perform the other regional soils in terms of total sales per unit area and provide better return for investment (Huffman, 1988). A comprehensive study by Onofrei et al. (1990) shows that in the Brown soil zone, farms on clay soils (cold Vertisols) are smaller than those regional soils, but in the Black soil zone, the opposite is observed. The land used for summer-fallow on clay soils is slightly less than the other soils for all the soil zones. This seems to agree with the suggestion that the clay soils are resistant to drought (Mitchell et al., 1944). 13.4.1. Crop selection and productivity Practically all of the farmland in the Lake Agassiz Basin (both in U.S.A. and Canada) is used for annual crop production The main crops grown on these clay soils are small grains (hard red spring wheat, barley, and oat), soybean and dry edible beans (mostly pinto) and sugar beet. Some 20 years ago, sunflower acreage increased dramatically with the release of hybrid varieties. Fluctuating price and

489

COLD VERTISOLS AND THEIR MANAGEMENT

500 km Fig. 13.3. Soil zones in the interior plains of western Canada.

problems with insects and diseases prevented sunflower from reaching predicted acreage levels. Some corn for grain is grown on the fringe where clay sediments grade toward coarser soil textures. In the interior plains of Canada, clay soils are used more commonly for cereal crops. On other soils preparation of cereal crops decreases in favor of forage crops (Onofrei et al., 1990). A common rotation in the Lake Agassiz Basin is barley-wheat-sugar beets. Sugar beet usually follow 2 years of grain to ensure reduced N levels. Another common rotation is alternative wheat and soybeans or dry beans. Areas of cold Vertisols, west of the Lake Agassiz Basin, are much smaller and usually used similarly to the soil in their neighborhood. In these areas, small grains and some sunflower are the main crops. Summer-fallow becomes more common with declining moisture levels. Intensive row cropping of the clay soils in southwestern Ontario (corn) has resulted in gradual deterioration of the surface soil structure (Stone, 1990). Current research focused on developing methods to improve soil structure, i.e. introducing grass and legume forages. The modeling procedure that was based on simulation techniques developed for land evaluation (Onofrei, 1986) indicated that in Manitoba wheat yield frequency distributions varied not only between heavy clay soils and lighter

A.R. MERMUT, D.D. PATTERSON and P.A. McDANIEL

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Fig. 13.4. Probability density curves of wheat yield on adjacent clay and loam soils. (A) southcentral black soil, (B) north of Black soil zone (gray zone).

textured soils, but also within the same textural group of the same soil zone (Onofrei et al., 1990). Figure 4 shows probability density curves of wheat yield on adjacent clay and loam soils in southcentral and north of the Black zone in Manitoba. It is clear that in southcentral Manitoba, the Red River clays out-perform the loam soils (Fig. 13.4A), whereas in the northern edge of the Black soil zone the loam soils seem to perform better (Fig. 13.4B). Onofrei et al. (1990), however, suggest that progress in yield development models can be improved by focusing on the soil characteristics, agronomic land attributes, including weed control, tillage, residue management, crop rotation, etc., climatic factors and their contribution to crop production. 13.4.2. Soil tillage The portion of the Lake Agassiz Basin in North Dakota and Minnesota a common rotation is barley-wheat-sugar beets. For small grains and after small grains, one fall tillage operation is carried out with a chisel plow and anhydrous ammonia application for weed control and seedbed preparation, leaving as much residue on the surface as possible for over-winter erosion control. Some farmers use a second tillage operation later in the fall for weed control, but one late fall tillage operation with the anhydrous ammonia application should eliminate this. The following spring, a field cultivator and drill are recommended as a single operation. Additional fertilizer is appHed with the drill if needed. Beet growers often use a disk after harvest for eliminating wheel tracks and levelling but a field cultivator is preferred. Disking reduces residue and promotes soil granulation and susceptibility to wind erosion. A one-pass spring tillage with field cultivator and anhydrous ammonia application is recommended for wheat after beans. For many years the moldboard plow was used extensively for fall tillage.

COLD VERTISOLS AND THEIR MANAGEMENT

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Chemical weed control was not available and plowing helped to curtail weed infestations. The freeze-thaw and wet cycles promote granulation and facilitate spring seeding. Fall plowing enables farmers to spread the work load and take full advantage of the relatively short time-period when conditions were optimum for spring seeding. Experiments conducted on annual cropping have shown that no one tillage practice method or tillage implement has been consistently the best, even on the same soil type (Geiszler et al., 1971). Several factors hkely play a role in this result: 1. Seedbed properties, resulting from the use of a given implement on a given soil, vary from one year to another. 2. Suitable seedbed properties may be developed in more than one way. 3. Desired seedbed properties for a given crop vary with prevailing climatic conditions during any part or over an entire growing season. 4. The effect of the tillage on crop performance is indirect, in that the tillage may ehminate competition, such as weeds, that is not an annual occurrence. Also tillage is only one aspect of the management system and its effect may be shadowed by other management practices. The development of large equipment allowed seeding to be done in less time and relieved the need for some fall tillage. Experience gained on the disadvantages of moldboard plowing and the adoption of chisel plows and field cultivators has led to its gradual decline over the last 20 years. While tillage is the traditional means of controlling weeds during the fallow year, excessive tillage can increase moisture and organic matter losses from the soil and consequently result in a decrease in crop production. It can greatly increase susceptibiHty of soil to erosion by destroying soil aggregates and by reducing the amount of crop residues retained on the surface (Campbell et al., 1990). One important consideration of an effective and non-degradative tillage system is optimizing its timing. Common practice in western Canada is fall and spring tillage. Increase in costs for machinery, labor and fuel has resulted in a change from conventional tillage to reduced tillage operations. Minimum or reduced tillage refers to the use of fewer tillage operations compared to conventional methods. While reduced tillage was conceived in Europe and the U.S.A. in the middle of this century, it was put in practice in the mid-1960's in the Canadian prairies. The use of discer, hoe-press drill and pneumatic seeders to seed directly into standing stubble are examples of minimum tillage. An extreme case is called zero tillage and it refers to the seeding of a crop into untilled stubble by causing no more soil disturbance than opening a sHt or a very narrow strip of soil, just enough to plant the seed. Chemical weed control is an essential part of this method. Zero or reduced tillage have several following potential benefits: (a) soil and moisture conservation, (b) weed control, (c) labour, equipment, fuel and energy saving. Reduced tillage systems are now practised successfully in many areas in the

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A.R. MERMUT, D.D. PATTERSON and P.A. McDANIEL

Canadian prairies. In some areas reduced tillage facilitates continuous cropping. 13.4.3. Water restriction on land use As in the other Vertisols that occur in warmer cUmates, soil water relation in cold Vertisols are also difficult to characterize, and water movement in clay soils is governed by macropore flow phenomena (Bouma, 1988). Volume change with water superimposes additional problems to study water flow in swelling soils. Free water moves along the cracks (macropores) and lateral infiltration of water into the soil may result in higher water availability. Studies in North Dakota indicate that the subsoil might have more available water (Bauer and Kucera, 1978). It is possible that the water storage at depth is in part related to bypass flow. In many Vertisols, because of waterlogging, crop productivity can be low. Surface drainage techniques are traditionally used to improve crop yield and stability. Surface water in the Lake Agassiz Basin is removed fairly effectively by a system of legal drains located on nearly all section fines, supplemented by a network of shallow, operator-maintained field drains, generally perpendicular to the legal drains. Field drains often intercept water from short laterals that extend to low areas in the microrelief. Cryerts outside the basin occur in areas of lower precipitation and are well or moderately well drained. Most areas are nearly level to sloping, and surface drainage is not a problem. Water management is important in the cold Vertisols occurring in the Brown and Dark Brown soil zones. As in other Vertisols, maintaining a surface cover would both increase infiltration and reduce evaporation. Fall tillage forms a granular mulch at the surface and can reduce evaporation considerably. Spring tillage may be effective in weed control and consequently reduction of water losses stored in the soil. However, as stated by Ahmad (1989), some cracking is important to allow a degree of aeration in the subsoil. Soil physical conditions seem to deteriorate under irrigated conditions. 13.4.4. Soil erosion Wind erosion is a problem in cold Vertisols in the U.S.A. and Canada, because of their tendency to become granular at the surface. It is believed that the surface granulation is also encouraged by freeze-thaw cycles, in addition to the influence of drying and wetting. Optimum residue management contributes to erosion control. Water conservation plays a major role in soil conservation. Any measures to conserve moisture would also be useful for soil conservation. Single-row tree belts are recommended for wind erosion control in the Lake Agassiz Basin and this is practised in other soils as well. Many farm operators recognizes the benefit of tree belts on coarse-textured soils, probably because the results of wind erosion on these soils are more spectacular. In the 1940's many tree belts were planted in the basin. Prohferation of tree belts in some areas, as opposed to others, was due to interest and effectiveness of the local soil conservationist of USDA-SCS in North Dakota. The number of

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494

A.R. MERMUT, D.D. PATTERSON and P.A. McDANIEL

tree belts, however, has decUned dramatically within the last 15 years. Tree belts have not been replaced as age, disease, insect damage, and aerial spraying have taken their toll. Also, some declining tree belts have been removed, and not replaced by farm operators who acquired larger equipment and preferred large fields. Erosion of Cryerts under cultivation can be very significant. In a study Mermut et al. (1983) have shown that under similar gradient, the thickness of the A horizon in the erosional portion of the slopes was less under cultivated than native grassland conditions, whereas in the depositional portion the thickness of the A horizon is greater under cultivation (Fig. 13.5). This is attributed to a granular surface and weakly developed subsurface soil structure which makes the soil susceptible to erosion when cultivated. Recent water transported soil material following heavy rains can be observed even in cultivated wheatland. Sheet erosion is very common during a heavy rain which may be followed by gullying. Drastic reduction in infiltration due to rapid aggregate destruction and swelling smectite which is the dominant silicate clay mineral in these soils, have been reported by Mermut et al. (1995) in Saskatchewan. Catastrophic levels of soil erosion can be observed in clay soil after continuous heavy rains (see Chapter 9). Landscape analysis has indicated that severe soil erosion under cultivation has provided values for sediment and organic matter losses that are in close agreement with estimates for medium textured Mollisols (Chernozemic soils) in Saskatchewan. The erosion equation developed for Cryerts indicated 7.4kgm~^yr~^ (0.57cmyr~^) for a 7.5 percent backslope and 2.1 kgm~^yr~^ (0.16cmyr~^) for 2 percent backslope. Under nearly 70 years of cultivation, Mermut et al. (1983) calculated losses of organic matter from the most severely eroded slopes about 650kgha~^yr""^ and comparable losses of nitrogen were 65 kg ha~^ yr~^ These values represent a 41 percent and 35 percent loss in organic matter and nitrogen respectively. Voroney et al. (1981) have estimated losses of 35 percent organic matter and 25-30 percent nitrogen in the Canadian Prairies. These values are somewhat lower than those reported for clay soils by Mermut et al. (1983). Severe erosion from cultivated Vertisol, especially on land > 3 percent slope, are reported in other parts of the world (Probert et al., 1987). Methods used to reduce the severe erosion are contouring, strip cropping and increasing ground cover by plant residues, and are also applied in Cryerts. Reduction in tillage, including zero tillage, and stubble retention are important soil conservation measures in Vertisols elsewhere (Freebairn and Wockner, 1983; Donaldson and Marston, 1984; Harte and Armstrong, 1984) and they will be very useful in Cryerts. 13.4.5. Other uses Vertisols are used for a number of other purposes in addition to those related to agriculture — building sites, road construction, sewage lagoons and septic waste absorption fields. The high shrink-swell potential and low bearing strength of these

COLD VERTISOLS AND THEIR MANAGEMENT

495

fine textured soils has contributed to the failure of numerous concrete structurefoundations, streets, sidewalks, and highways. Asphalt road surfaces tend to slump on sloping gradients. Effluent from sewage lagoons tends to move through varved areas and resurface outside the lagoon. The high clay content of these soils limits the rate at which septic effluent is adsorbed in conventional fields. Changes in the design of these structures have alleviated many problems.

REFERENCES Ahmad, N., 1989. Management of tropical Vertisols. In: P.M. Ahn and C.R. Elliott (Editors) Vertisol Management of Africa, IB SRAM Proceedings No. 9, Bangkok, Thailand, pp. 29-62. Bauer, A. and Kucera, H.L., 1978. Effect of tillage on some soil physicochemical properties and on annually cropped spring wheat yields. Bulletin 505, Agricultural Experimental Station, North Dakota State University, Fargo, ND, U.S.A., 102 pp. Bouma, J., 1988. Characterizing soil water relationships in swell-shrink soils. In: L.R. Hirekerur, J.L. Sehgal, D.K. Pal and S.B. Deshpande (Editors) Classification Management and Use Potential of Swell-shrink Soils, Oct. 24-28, 1988. NBSS-LUP, Nagpur, India, Oxford and IBH Publ. Co. Pvt., Ltd., New Delhi, pp. 83-95. Brierley, J.A., Mermut, A.R. and Stonehouse, H.B. 1996. Vertisolic soils: A new order in the Canadian System of Soil Classification. Agriculture and Agrifood Canada, Ottawa, ON, Contr. No. 96-11, 76 pp. Campbell, C.A., Zentner, R.P., Janzen, H.H. and Bowren, K.E., 1990. Crop rotation studies on the Canadian prairies. Research Branch, Agriculture Canada, Publ. 1841/E, pp. 133. Dasog, G.S., 1986. Properties, genesis and classification of clay soils in Saskatchewan. Ph.D. Thesis, University of Saskatchewan, Saskatoon, SK, Canada, 177 pp. Dasog, G.S., Acton, D.F. and Mermut, A.R., 1987. Genesis and classification of clay soils with vertic properties in Saskatchewan. Soil Sci. Soc. Amer. J., 51: 1243-1250. Dasog, G.S., Acton, D.F., Mermut, A.R. and de Jong, E. 1988. Shrink-swell potential and cracking in clay soils of Saskatchewan. Can. J. Soil Sci., 68: 251-260. Donaldson, S.G. and Marston, D., 1984. Structural stability of black cracking clays under different tillage system. In: J.W. McGarity, E.H. Hoult and H.B. So (Editors) The Properties and Utilization of Cracking Clay Soils. Reviews in Rural Science 5, University of New England, Armidale, Australia, 335-338. Dubbin, W.E., Mermut, A.R. and Rostad, H.P.W., 1993. Clay mineralogy of parent materials derived from uppermost Cretaceous and Tertiary sediment rocks in southern Saskatchewan. Can. J. Soil Sci., 73: 447-457. Ellis, J.H. and Caldwell, O.G., 1935. Magnesium clay Solonetz. Trans. Int. Congr. Soil Sci., 3rd 1: 348-350. Fredlund, D.G., 1975. Engineering properties of expansive clays. Internal Research Report (IR-7), Transportation and Geotechnical Group, Dept. of Civil Engineering, University of Saskatchewan, Saskatoon, SK, Canada. Freebairn, D.M. and Wockner, G.G, 1983. Soil erosion control research provides management answers. Queensland Agricultural J., 109: 227-234. Geiszler, G.N., Hoag, B.K., Bauer, A. and Kucera, H.L. 1971. Influence of seed-bed preparation on some soil properties and wheat yields on stubble. North Dakota Agric. Exp. Stn. Bull. 488.

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Harte, A.J. and Armstrong, J.L., 1984. Trends in runoffs and soil related parameters from a stubble management trial on a dark self-mulching soil, north-western N.S.W. In: J.W. McGarity, E.H. Hoult and H.B. So (Editors) The Properties and Utilization of Cracking Clay Soils, Review in Rural Science 5, University of New England, Armidale, AustraUa, pp. 363-368. Huffman, E., 1988. A description of physical and economic strategies of farming in the major soil zones of Canadian Prairies. In: J. Dumanski and V. Kirkwood (Editors) Crop Production Risks in the Canadian Prairie Region in Relation to Climate and Land Resources, Technical Bull., 1988-5E, LRRC, Research Branch, Agriculture Canada, Ottawa, ON, pp. 17-30. Kodama, H. Ross, G.J., Wang, C. and Macdonald, K.B., 1993. Clay mineralogical database of Canadian soils with a clay mineralogical map of surface soils. Agriculture Canada Research Branch, Tech. Bull. 1993-lE, CLBRR Contr. 92-82, Ottawa, ON., 67 pp. Lamontagne, L. and Cossette, J.-M., 1994. Vertisolic soils field tour in east of Canada (Quebec portion). Agriculture Canada, Sainte-Foy, Quebec, PQ. Mermut, A.R. and Acton, D.F., 1985. Surficial rearrangement and cracking in swelling clay soils of the glacial lake Regina basin in Saskatchewan. Can. J. Soil Sci., 65: 317-327. Mermut, A.R. and St. Arnaud, R.J., 1983. Micromorphology of some Chernozemic soils with grumic properties in Saskatchewan, Canada. Soil Sci. Soc. Amer. J., 47 536-541. Mermut, A.R. and Arshad, M.S., 1987. Significance of sulfide oxidation in soil salinization in southeastern Saskatchewan, Canada. Soil Sci. Soc. Amer. J., 51: 247-251. Mermut, A.R., Acton, D.F. and Eilers, W.D., 1983. Estimation of soil erosion and deposition by a landscape analyses technique on clay soils in southwestern Saskatchewan. Can. J. Soil Sci., 63, 727-739. Mermut, A.R., Ghebre-Egziabhier, K. and St. Arnaud, R.J. 1984. The nature of smectites in some fine textured lacustrine parent materials in southern Saskatchewan. Can. J. Soil Sci., 64: 481-494. Mermut, A.R., Acton, D.F. and Tarnocai, C , 1990. A review of recent research on swelling clay soils in Canada. In: J.M. Kimble (Editor) Proceedings of the Sixth International Soil Correlation Meeting, Characterization Utilization of Cold Aridisols and Vertisols, USDA, SCS, National Soil Survey Center, Lincoln, NE, pp. 112-121. Mermut, A.R., Luk, S.H., Romkens, M.J.M. and Poesen, J.W. 1995. Micromorphological and mineralogical components of surface sealing in loess soils from different geographic regions. Geoderma, 66: 71-84. Mills, G.F., Eilers, R.G. and Veldhuis, H., 1990. Thermal regime and morphology of clay soils in Manitoba, Canada. In: J.M. Kimble (Editor) Proceedings of the Sixth International Soil Correlation Meeting, Characterization Utilization of Cold Aridisols and Vertisols, USDA, SCS, National Soil Survey Center, Lincoln, NE, pp. 122-132. Mitchell, J., Moss, H.C. and Clayton, J.S., 1944. Soil Survey of Southern Saskatchewan, Soil Survey Report No. 12, University of Saskatchewan, Saskatoon, SK, Canada, 259 pp. Onofrei, C , 1986. A Method of Land Evaluation Using Crop Simulation Techniques. Ph.D. Thesis, University of Manitoba, Winnipeg, MB, Canada. Onofrei, C , Dumanski, J., Eilers, R.G. and Smith, R.E. 1990. A comparison of land use and productivity of clay and loam soils within the interior plains of western Canada. In: J.M. Kimble (Editor) Proceedings of the Sixth International Soil Correlation Meeting, Characterization Utilization of Cold Aridisols and Vertisols, USDA, SCS, National Soil Survey Center, Lincoln, NE, pp. 138-145.

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Probert, M.E., Fergus, I.E., Bridge, B.J., McGarry, D., Thompson, C.H. and Russell, J.S., 1987. The Properties and Management of Vertisol. C.A.B. International, Oxon, U.K., 20 pp. Ripley, E.A., 1973. Canadian Committee for the International Biological Programme. Matador Project Tech. Rep. No. 12, Description of Site: II. Climatology of the Matador Area. University of Saskatchewan, Saskatoon, SK, Canada. Soil Survey Staff., 1994. Key to Soil Taxonomy. 6 Ed. USDA, SCS, Government Printing Office, Washington, D.C., 306 pp. Staff Saskatchewan Soil Survey., 1984. The Soils of Wolseley Rural Municipahty No. 155. Saskatchewan, Agriculture Canada, Sask Agriculture. Stone, J.A., 1990. Soil management research on the clay soils of southwestern Ontario — a review. In: J.M. Kimble (Editor) Proceedings of the Sixth International Soil Correlation Meeting, Characterization Utilization of Cold Aridisols and Vertisols, USDA, SCS, National Soil Survey Center, Lincoln, NE, pp. 197-203. Tarnocai, C , Mills, G.F., Veldhuis, H., Lutmerding, H. and Green, A., 1990. Clay soils of northern Canada and the Cordillera. In: J.M. Kimble (Editor) Proceedings of the Sixth International Soil Correlation Meeting, Characterization Utilization of Cold Aridisols and Vertisols, USDA, SCS, National Soil Survey Center, Lincoln, NE, pp. 208-226. Thompson, C.H. and Beckmann, G.G., 1982. Gilgai in Austrahan black earths and some of its effects on plants. Trop. Agric, 59: 149-156. Voroney, P.R., van Veen, J.A. and Paul, E.A., 1981. Organic C dynamics in grassland soils. 2. Model vaHdation and simulation of the long-term effects of cultivation and rainfall erosion. Can. J. Soil Sci., 61: 211-224. Wilding, L.P., WiUiams, D., Miller, R.D., Cook, T. and Eswaran, H., 1990. Close interval spatial variability of Vertisols: A case study in Texas. In: J.M. Kimble (Editor) Proceedings of the Sixth International Soil Correlation Meeting, Characterization Utilization of Cold Aridisols and Vertisols, USDA, SCS, National Soil Survey Center, Lincoln, NE, pp. 232-247. Young, R.A., Zubriski, J.C. and Norum, E.B., 1960. Influence of long-term fertility management practices on chemical and physical properties of a Fargo clay. Soil Sci. Soc. Amer. P r o c , 24: 124-128.