Soil Management Handbook - Ministry of Agriculture and Lands

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Figure 3 Schematic drawing of root growth in well-structured (left) and poorly-structured soil (right) physical forces. In soils under cultivation, most aggregates at the surface tend to break down under the forces of rainfall, tillage and traffic. Soil structure also influences the internal drainage of the soil, affects its water-holding capacity, temperature and resistance to the growth of plant roots and the emergence of seedlings. The formation of soil structure and factors which influence its breakdown are discussed in Section 2.1. 1.4 Porosity The porosity, or % pore space, in soils is the portion of the soil mass occupied by air and water. Porosity is determined by both soil texture and structure, and therefore, porosity is influenced by practices which alter soil structure. The size and distribution of pores in the soil is very important in determining the rates of air and water movement in soils, as well as influencing root growth. Plant roots require a balance of air and water for optimum growth. Very small (micro) pores tend to restrict air and water movement while large (macro) pores promote good air and water movement. Sandy soils have a low porosity (35 to 50% by volume), but the pores are relatively large. As a result of this, sandy soils tend to drain rapidly, to retain little water and to be well-aerated. Medium and fine-textured soils have higher porosity (40 to 60% by volume), and a high proportion of the pores are small. These soils tend to retain more water, to drain more slowly and to be less well-aerated. In finer-textured clay soils, those approaching 60% porosity with a predominance of small pores; structure and porosity, restrict air and water movement. In these soils, it is desirable to create larger pores by promoting a granular structure. In addition to the effects of texture and structure on soil porosity, the activities of soil organisms is of equal importance. The burrowing activities of worms and soil insects result in the formation of larger pores which are beneficial to most soils. Practices which encourage the activity of soil organisms are of some practical significance in the management of finer-textured soils. Soil Management Handbook – Okanagan-Similkameen Valleys 35
Table 6 Physical Characteristics of Soil Textural Groups Soil Textural Group Soil Textures and Types Characteristics Coarse to Moderately Coarse Medium Moderately Fine to Fine and Very Fine Organic Soils Gravel Sand Loamy Sand Sandy loam Fine Sandy Loam Very Fine Sandy Loam Loam Silty Loam Silt Sandy Clay Loam Clay Loam Silty Clay Loam Sandy Clay Clay Silty Clay Heavy Clay Muck and Peat Loose and friable when moist or wet. Loose to soft when dry. Very high proportion of large pores. Low water-holding capacity. Good bearing strength and trafficability when wet. Tends to form weak clods when cultivated. Easy to maintain good tilth. Slightly sticky and plastic when wet. Friable to firm when moist, soft to slightly hard when dry. Moderately easy to maintain good tilth. Moderately good trafficability and bearing strength when wet. Tends to form small to medium, slightly firm clods when cultivated. High proportion of medium to small pores, high water-holding capacity and available water. Sticky and plastic when wet. Friable to firm when moist, hard to very hard when dry. High proportion of small pores. Moderately difficult to maintain good tilth. Poor trafficability when wet. Tends to form large, firm clods when cultivated. High water-holding capacity, but less available water than medium-textured soils. Variably sticky, usually non-plastic, friable, slightly firm when dry. Very high water-holding capacity. Poor trafficability when wet. Tends to form small to medium clods when cultivated. Easy to maintain good tilth. 36 Soil Management Handbook – Okanagan-Similkameen Valleys
Page 2 and 3: Soil Management Handbook For The Ok
Page 4 and 5: Preface The Soil Management Handboo
Page 6 and 7: Table Of Contents Preface..........
Page 8 and 9: Table of Contents Con't. Page 3.6 D
Page 10 and 11: List Of Soil Management Groups And
Page 12: List Of Tables Table1: Farm Conserv
Page 15 and 16: To obtain information about the soi
Page 17 and 18: List of Definitions for Table 1 Con
Page 19 and 20: Well Suited Crops • All necessary
Page 21 and 22: Soil Depth refers to the depth to e
Page 23 and 24: Grapes: grape suitability is strong
Page 25 and 26: Soil Management Groups This section
Page 27 and 28: Gammil Soil Management Group Soil S
Page 29 and 30: Greata Soil Management Group Soil S
Page 31 and 32: Kelowna Soil Management Group Soil
Page 33 and 34: Munson Soil Management Group Soil S
Page 35 and 36: Postill Soil Management Group Soil
Page 37 and 38: Rumohr Soil Management Group Soil S
Page 39 and 40: Skaha Soil Management Group Soil Se
Page 41 and 42: Summerland Soil Management Group So
Page 43 and 44: Miscellaneous Soils Soil Series: Ar
Page 45 and 46: Soil Management Guide This section
Page 47: Table 5 Soil Particle Size and Char
Page 51 and 52: plant roots and organic matter. The
Page 53 and 54: 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 and 106:
Appendix A-2 Figure 2 Typical summe
Page 107 and 108:
Appendix A-4 fall frost. The angle
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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