Soil Management Handbook - Ministry of Agriculture and Lands

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Solar Radiation Solar energy is the primary source for all biological processes. Radiation from the sun has an effect on air and soil temperature, transpiration, soil moisture, atmospheric humidity, all plant processes, cell division, topism and factors such as sugar accumulation, bud fertility, wood maturity, etc. Yield and quality are also influenced. The amount of solar radiation received at a site and the duration of sunshine during the growing and harvesting season has a direct influence on all these factors. Shading from the afternoon and evening sun in mountainous areas, caused by topography or nearby trees, may have a negative effect on crop quality. Solar radiation is associated with heat summation at particular sites and factors such as the length of the growing season, although not directly related with heat accumulation, are associated with solar radiation. Long growing seasons with low heat unit accumulations are found in cool growing areas such as coastal climates where solar radiation is limited. In cool climate areas, such as the Pacific Northwest, the selection of sites for some high value crop production must take into account slopes; aspects; elevation above sea level; protection from winds; proneness to fog in spring or fall; the best sources of solar radiation; and hence, increased heat accumulation and sunlight. The effect of solar radiation is also noticed on soils. Soil texture and soil water content differences can influence the heating and cooling rates in crop production. Dry, sandy soils have the greatest range of daytime to nighttime temperatures. Clay soils at field capacity have the least fluctuation in temperature. These differences are greatest close to the soil where only a few centimeters change in elevation can be responsible for significant differences in temperatures. The table below gives an indication of the effect of surface cover on temperatures within a crop. The use of soil textures, soil moisture and soil cover for frost protection is an established practice. For example, wetting a dry soil improves the transfer of heat from the atmosphere to the soil and at the same time increases the heat storage capacity in the soil proportional to the volume it contains. Imposing a living vegetation barrier between the soil and the atmosphere reduces the transfer of heat to the soil. The amount of radiation lost as heat from soil varies with the shape of valleys. Depressions are traditionally frost pockets, however, narrow, steep valleys, such as the Okanagan and Similkameen Valleys, tend to restrict the amount of radiation. Soil heat is transferred to the atmosphere in large amounts due to the relatively large ground surface area. The location of Okanagan Lake and the chain of lakes located in the Okanagan Valley contribute significantly to the collection and release of thermal radiation and cloud formation. Increased cloud cover, particularly in winter months, reduces the outgoing radiation keeping the area warmer than the surrounding plateau. Effects of Soil Surface Cover on Temperature Within a Crop Surface Cover Temperature (°C) Bare, firm, moist soil Warmest Shredded cover crop, moist soil 1/2 degree cooler Low cover crop, moist soil 1/2 degree cooler Dry, firm soil 1 degree cooler Freshly disced soil 1 degree cooler High cover crop 1 to 2 degrees cooler Slope and Aspect Appendix A-3 The amount of solar radiation accumulated at a site varies depending on the slope of the land and the direction of the slope. In the northern hemisphere, southern slopes are the best choice to gain increased solar radiation. North facing slopes gain the least while west slopes intercept more solar radiation than east slopes. Total accumulated heat units are generally greatest near the midslope, less on the hilltops and lowest near the base of the slope. Exposed hill tops have lower maximum temperatures and slightly cooler minimum temperatures than midslopes. Cold air flows down slopes and collects at the base creating frost pockets and areas with late spring frost and early
Appendix A-4 fall frost. The angle of the slope, in relation to the location of the sun, is very important to maximize the amount of solar collected at a site. Figure 3 illustrates the effect of the slope on the amount of solar radiation collected at Summerland. South slopes may lose the protective snow cover in winter months, resulting in root damage from penetrating frost on light sandy soils. South slopes may demonstrate advanced bud break and increased water requirements. In warm areas of the Pacific Northwest, south slopes may be too warm for certain crops or varieties. In contrast, the growing season and winter conditions on north facing slopes are all negative except for slopes of less than 10 degrees. Such slopes in warm areas may be useful only for some early maturing crops or varieties. Figure 3 Total growing season solar radiation (MJ/m 2 ) at Summerland as a function of slope and aspect Source: Atlas of Suitable Grape Growing Locations in the Okanagan and Similkameen Valleys Elevation Crops are grown over a wide range of elevations in the Okanagan. There are limits in elevation above sea level (ASL) where some crops can be grown economically. Increases in elevation of 100 metres may reduce the average annual temperature by as much a 1°C. For example, 660 metres ASL is considered to be the cut off for tree fruits in the Okanagan. Exceptions have been noted on south slopes and in areas where air inversions may form. Fields at higher elevations are, therefore, generally cooler than fields at lower elevations in the same region. Higher elevations are generally wetter due to increased precipitation during the growing season and winter months. Cooler temperatures at higher elevations delay bud break, flowering and ripening dates.
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Soil Management Handbook For The Ok
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Preface The Soil Management Handboo
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Table Of Contents Preface..........
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Table of Contents Con't. Page 3.6 D
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List Of Soil Management Groups And
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List Of Tables Table1: Farm Conserv
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To obtain information about the soi
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List of Definitions for Table 1 Con
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Well Suited Crops • All necessary
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Soil Depth refers to the depth to e
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Grapes: grape suitability is strong
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Soil Management Groups This section
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Gammil Soil Management Group Soil S
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Greata Soil Management Group Soil S
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Kelowna Soil Management Group Soil
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Munson Soil Management Group Soil S
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Postill Soil Management Group Soil
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Rumohr Soil Management Group Soil S
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Skaha Soil Management Group Soil Se
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Summerland Soil Management Group So
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Miscellaneous Soils Soil Series: Ar
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Soil Management Guide This section
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Table 5 Soil Particle Size and Char
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Table 6 Physical Characteristics of
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plant roots and organic matter. The
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The bulk density of high organic mi
Page 55 and 56: Other management practices, such as
Page 57 and 58: Figure 11 Schematic drawing of the
Page 59 and 60: 1 m, etc., in an orchard block wher
Page 61 and 62: 3. Water Management High rainfall d
Page 63 and 64: Table 12 Availability Coefficients
Page 65 and 66: Impact of large drops of water disp
Page 67 and 68: The single most important soil fact
Page 69 and 70: land. Drainage systems are also nec
Page 71 and 72: Detailed information is provided in
Page 73 and 74: Table 16 Generalized Soil Profile D
Page 75 and 76: Table 17 Drain Recommendations Base
Page 77 and 78: is very susceptible to structure de
Page 79 and 80: vertically into the soil and as it
Page 81 and 82: Figure 19 Schematic drawing of the
Page 83 and 84: Case 1: Well Structured Soils If th
Page 85 and 86: fracture requires the soil to expan
Page 87 and 88: "tie up" some soil nitrogen, althou
Page 89 and 90: efer to the following Factsheets: S
Page 91 and 92: contaminate groundwater. Water cont
Page 93 and 94: Table 18 N, P and K Content of Vari
Page 95 and 96: field access is possible, manure ap
Page 97 and 98: Annual or permanent cover will redu
Page 99 and 100: agricultural production, its impact
Page 101 and 102: References Published Sources Agricu
Page 103 and 104: Stevenson, D.S. and Brownlee, C.H.
Page 105: Appendix A-2 Figure 2 Typical summe
Page 109 and 110: Appendix A-6 Abbreviations Used in
Page 111 and 112: Appendix B: Soil Series And Locatio
Page 113 and 114: Greata Soil Management Group Greata
Page 115 and 116: Postill Soil Management Group Eanea
Page 117 and 118: Miscellaneous Soils Armstrong (A:er
Page 119: FOR FURTHER INFORMATION CONTACT B.C
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Soil Management Handbook - Ministry of Agriculture and Lands

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