Certified Crop Advisor Western Region Exam With 100% Correct Answers

Certified Crop Advisor Western Region Exam With 100% Correct Answers Size of sand and its characteristics - answer.05mm to 2.0mm, lower CEC, lower water holding capacity Size of silt - answer.002mm - .05mm Size of Clay - answerless than .002mm Define bulk density - answerthe ratio of the mass of soil to its bulk volume. expressed in g/cm3 How does bulk density differ with soil texture - answersandy soil has higher bulk density because has less overall pore space. Bulk density ranges of sand - answer1.2-1.8 g/cm3 Bulk density range for silt and clay - answer1.0-1.6 g/cm3 How does bulk density affect soils and plant growth - answerIncreased bulk density = more compaction, root growth impaired, aeration and waster infiltration impaired How does bulk density affects the interpretation of nitrate levels - answeroxygen supply and mineralization are slowed. Dry soil sample below 100 degrees F with soil sample . Increase over time if soil is moist. Soil structure - answerArrangement of soil particles into groupings. Soil aggregates - answerthe groupings of soil particles Different types of soil structure - answergranular, blocky, prismatic, platy list benefits of well-developed aggregates - answersmall particles clump together to form more macrospores = better infiltration, aeration, provides habitat for various microorganism, bulk density how do soil organisms and soul organic matter affect soil strucutre - answeraggregation formed by physical and chemical processes. Soil microorganisms excrete substances that act as cementing agents and bind soil particles together. Fungi have filaments, called hyphae, which extend into the soil and tie soil particles together. Roots also excrete sugars into the soil that help bind minerals. How does soil management affect soil structure - answerAdding gypsum (Ca2+) = electrostatic attraction binds soil tillage = breaks up aggregates, increases rates of decomposition reducing soil OM Cover crops/manures build OM How does exchangeable sodium affect soil aggregation and waste movement in soils - answerhigh NA+ concentration displaces Ca2+ in soil. Sodium cannot bind soil particles because it is a monovalent ion, which results in deflocualtion and reduced water infiltration. Makes leaching difficult How does soil salinity affect soil aggregation and water - answersoluble salts. increase salinity but Na is a small fraction of cation no serious soul structure or drainage issues How structure can affect root growth - answerpoor structure, increases compaction, reduces rooting depth/accumulation of nutrients, drain poorly/waterlogged How does soil organic matter (SOM) affect soil aggregation - answerincreased OM increases aggregation through physical and chemical processes SOM affect on water holding capacity and infiltration - answerincreases pore space/network of pores allowing for infiltration and waster holding capacity. Like a sponge. a 1% increase in OM, increases water holding capacity by how much - answer3,400 gallons per acre (3.7% increase) SOM affect on Cation exchange capacity - answerincreasing OM increases CEC because OM in negatively charged How OM is related to temperature - answerincrease in temp, results in rapid decomposition of OM. colder climates generally have higher OM % Role of OM in pesticide movement - answerOM binds pesticides and can make them less active cation exchange capacity - answera measure of the soil's ability to hold positively charged ions. List three ways to maintain OM - answerreduce tillage, cover crops, avoid soil compaction and keep proper ph Importance of soil OM in nutrient management - answerCEC, mineralization C:N ratio, 3% of soil OM overturns each year Define salt - answerany ionic compound whose cation comes from a base and it's anion comes from an acid a user of irrigation water should know the effects that water quality and irrigation practices have on what (6 elements)? - answersalt content (salinity) of soil sodium status (sodicity) of soil rate of water infiltration toxic element content of soil soil nutrient status plugging of microirrigation systems define parts per million - answer1 part of salt to 1 million parts of water define milliequivalents per liter - answera measurement of charge concentration per liter convert ppm to meq/l - answerppm = equivalent weight x meq/l Define saline soil - answera soil containing enough soluble salts to interfere with plant growth, but not containing an excess of exchangeable sodium Define salinity - answerthe amount of salt dissolved in water Define sodium absorption ratio (SAR) - answerratio of sodium to the sum of calcium and magnesium, measured on the basis of cation charges Define electrical conductivity - answermeasure of the bulk salinity in soil (ECe) or water (ECw) What is the formula for SAR - answerSAR= Na/Square root of Ca+Mg/2 (%) Define total dissolved solids - answerthe measure of bulk salinity, usually only used for water (PPM) calculate how much salt is applied per acre foot of water? - answersalts applied in lbs = TDS x 2.72 how many gallons is an acre foot of water - answer326,000 gallons Define exchangeable sodium percentage (ESP) - answerPercentage of cation charges represented by sodium Formula for ESP - answer(Na/sum of base cations)x100 Electrical conductivity of a saline soil - answergreater than 4 ds/m Exchangeable sodium percentage (ESP) of a saline soil - answerless than 15 % pH of a saline soil - answerless than 8.5 Sodium absorption ratio (SAR) of a saline soil - answerless than 13 Define a sodic soil - answersodium concentration high enough to adversely affect structure, while overall salt concentration is below saline threshold Electrical conductivity of a sodic soil - answerless than 4 EC pH of a sodic soil - answergreater than 8.5 Exchangable sodium percentage of a sodic soil - answerGreater than 15 Sodium absorption ratio of a sodic soil - answergreater than 13 Define a saline-sodic soil - answeroverall salt concentration high enough to reduce crop growth, together with sodium concentration high enough to damage soil structure EC of a saline-sodic soil - answergreater than 4 ds/m Soil pH of a saline-sodic soil - answerless than 8.5 SAR of a saline-sodic soil - answergreater than 13 ESP of a saline-sodic soil - answergreater than 15 convert EC less tahan 5 ds/m to TDS - answerEC X 640 convert EC more than 5 ds/m to TDS - answerEC X 800 calculate the total pounds of dissolved salts applied per acre foot of water? - answerTDS x 2.72 Explain how growth stage of crops can affect its salt tolerance - answerPlants are less salt tolerant as seedlings, during transplanting explain relationship between SAR and ESP - answernumbers are numerically similar, with ESP marginally higher. at what ECw (ds/m) is there no,slight to moderate, and severe restriction of use in water quality for irrigation in regards to salinity - answerless than 0.7, 0.7 - 3, greater than 3 at what TDS (ppm) is there no, slight to moderate, and severe restriction of use in water quality for irrigation in regards to salinity - answerless tahn 450, 450-2,000, greater than 2,000 when SAR is 0-3 at what ECw is infiltration problems unlikely to occur and likely - answerunlikely = ECw is more than 0.6