Field Guide. cropping and pastoral grazing on flat to rolling country.

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SOIL INDICATORSNumber <strong>and</strong> colour of soil mottles under pasture Assess the number, size <strong>and</strong> colour of mottles by comparing the sideof the soil profile, or a number of soil clods from the soil structuretest, with the three photographs opposite.Mottles are spots or blotches of different colour interspersed withthe dominant soil colour.The percentage chart below will help you determine the percent ofthe soil occupied by mottles.THE NUMBER, SIZE AND COLOUR OF MOTTLES indicate how wellthe soil is drained <strong>and</strong> how well it is aerated. They are also an earlywarning of a decline in soil structure, <strong>and</strong> show whether the soil is beingdamaged by pugging. Loss of soil structure reduces the number ofchannels <strong>and</strong> pores in the soil that conduct air <strong>and</strong> water. This results ina deficiency of oxygen <strong>and</strong> a build-up of carbon dioxide. As oxygendepletion increases, orange <strong>and</strong> ultimately grey, mottles form. A highproportion of grey mottles indicates the soil is waterlogged <strong>and</strong> starvedof oxygen for much of the year. Poor aeration reduces the uptake ofwater <strong>and</strong> plant nutrients, particularly nitrogen, phosphorous <strong>and</strong>potassium. Poor aeration also retards the breakdown of organicresidues, <strong>and</strong> can induce chemical reactions that form chemicals toxicto plant roots.62 VISUAL SOIL ASSESSMENT: Volume 1
FIGURE 4: Visual scoring (VS) of number <strong>and</strong> colour of soil mottles under pasturePOOR CONDITION VS = 0Soil has abundant to profuse (>50%),medium <strong>and</strong> coarse orange <strong>and</strong> greymottlesMODERATE CONDITION VS = 1Soil has common (10-25%) fine <strong>and</strong>medium orange <strong>and</strong> grey mottlesGOOD CONDITION VS = 2Mottles are generally absentVISUAL SOIL ASSESSMENT: Volume 163
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VISUAL SOILASSESSMENTCROPPED SOILPA
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TABLE OF CONTENTSIntroduction 5Visu
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INTRODUCTIONTHE QUESTION - To profi
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The following examples illustrate t
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2. Setting upIt is important to be
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Page 14 and 15: SCORE CARDVisual indicators for ass
Page 16 and 17: SOIL INDICATORSSoil structure <stro
Page 18 and 19: SOIL INDICATORSSoil porosity under
Page 20 and 21: SOIL INDICATORSSoil colour under <s
Page 22 and 23: SOIL INDICATORSNumber and</
Page 24 and 25: SOIL INDICATORSEarthworm counts und
Page 26 and 27: SOIL INDICATORSPresence of a tillag
Page 28 and 29: SOIL INDICATORSDegree of clod devel
Page 30 and 31: SOIL INDICATORSSusceptibility to wi
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Page 34 and 35: PLANT INDICATORSCrop emergence Asse
Page 36 and 37: PLANT INDICATORSCrop height at matu
Page 38 and 39: PLANT INDICATORSThe size an
Page 40 and 41: PLANT INDICATORSCrop yield Assess r
Page 42 and 43: PLANT INDICATORSRoot diseases Asses
Page 44 and 45: PLANT INDICATORSWeed infestation As
Page 46 and 47: PLANT INDICATORSSurface ponding und
Page 48 and 49: PLANT INDICATORSProduction costs As
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Page 53 and 54: SCORE CARDVisual indicators for ass
Page 55 and 56: INSTRUCTIONS FORASSESSING SOIL QUAL
Page 57 and 58: FIGURE 1: Visual scoring (VS) of so
Page 59 and 60: FIGURE 2: Visual scoring (VS) of so
Page 61: FIGURE 3: Visual scoring (VS) of so
Page 65 and 66: FIGURE 5: Visual scoring (VS) of ea
Page 67 and 68: FIGURE 6: Visual scoring (VS) of su
Page 69 and 70: INSTRUCTIONS FORASSESSING SOIL QUAL
Page 71 and 72: FIGURE 7: Visual scoring (VS) of pa
Page 77 and 78: FIGURE 10: Visual scoring (VS) of a
Page 79 and 80: FIGURE 11: Visual scoring (VS) of d
Page 81 and 82: FIGURE 12: Visual scoring (VS) of s
Page 83 and 84: FIGURE 13: Scoring of stock-carryin
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Field Guide. cropping and pastoral grazing on flat to rolling country.

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