AGRONOMY 375. October 2, Exam 1

Transcription

1 Name AGRONOMY 375 October 2, 2015 Exam 1 There are 14 questions. One bonus question is also included at the end of the exam. A total of 100 points is possible. Best wishes for your success! 6 pts 1. What can a grain crop producer measure/compare to learn how near optimum efficiency they are with the input mix for zones within their fields? Please explain. 4 pts. 2. Is management to optimize crop input use efficiency (as referred to in question 1 above) profitable and consistent with good environmental stewardship and sustainability? Please explain. Assume crop management for the long run (i.e. greater than 10 years). 12 pts. 3. Describe GPS, GIS,VRT and RTK and integrate them into one example which illustrates their use in working toward the achievement of Maximum Economic Yield.

2 8 pts. 4. If managing a field in zones (not soil sampling on a grid), what two major considerations should be kept in mind to determine where within a field soil samples should be collected to accurately represent P and K levels as a basis for routine fertilizer recommendations in these zones? a) b) 5 pts. 5. a) What soil sampling depth is to be used for the determination of P and K soil test levels as a basis for routine P and K fertilizer recommendations (per the field calibration trials contributing to the Tri-State Fertilizer recommendations published by Purdue, Ohio State and Michigan State)? 2 pts. b) If sampling on a grid what is the distance between grid sampling midpoints (nodes) when each grid unit is 3 acres in size? Please show your work. 4 pts. 6. a) What Critical Level () is recommended as an economic goal (average conditions) for Phosphorus P1 soil tests for corn and soybean production in Indiana? 4 pts. b) What annual Buildup recommendation (pounds P / acre) should be made to increase the P1 soil test level from 9 to the Critical Level. (Buildup component only. Please do not include a maintenance component). 4 pts. 7. a) What Critical Level () is recommended as an economic goal (average conditions) for Potassium soil tests for corn and soybean production on a soil with a C.E.C. of 16? 4 pts. b) What annual Buildup recommendation (pounds K 2 0 / acre) should be made to increase the soil test level from 90 exchangeable K to the Critical Level? (Buildup component only. Please do not include a maintenance component). 2

3 12 pts. 8. The average economic goal (critical P1 or K soil test level) is at the leading edge of the Maintenance Plateau in planning soil fertility for crop production. a) What is the upper limit (maximum value) of the P1 soil test maintenance range or plateau for corn and soybean production under average conditions as in question 7 above? b) What is the upper limit of the P1 soil test drawdown range for corn and soybean production under average conditions as in question 7 above? c) What is the upper limit (maximum value) of the K soil test maintenance range or plateau for corn and soybean production under average conditions on a soil with a CEC of 16 as in question 7 above? d) What is the upper limit (maximum value) of the K soil test drawndown range for corn and soybean production under average conditions on a soil with a CEC of 16 as in question 7 above? 3 pts. 9. Please distinguish between active and passive symptom expression with respect to cause and effect crop diagnostic relationships (provide an example of each). 3 pts. 10. Please distinguish between primary and secondary with respect to cause and effect crop diagnostic relationships (provide an example of each). 4 pts. 11. Briefly describe a procedure by which percent surface residue cover in a field can be measured using equipment commonly available on a farm. 4

4 9 pts 12. Please note three factors that lessen soil erosion due to the movement of runoff water in conservation or reduced tillage production system (e.g. no-till coulter planted corn or soybeans) versus a conventional tillage corn production system (e.g. fall twist chisel plow plus 2 X field cultivations prior to planting in the spring). Assume the previous crop is corn in both systems. a) b) c) 8 pts 13. Describe two early - growing season differences in the physical properties of the upper soil profile (e.g. top few inches) under a no-till and a conventionally plowed field in a poorlydrained central Indiana soil. Please also note how they influence early root development by corn or soybean plants. 8 pts 14. Please list four possible benefits/goals for the use of cover crops in a corn and soybean production system. a) b) c) d) 5 pts. BONUS What considerations might suggest that in some well-defined zones) within a field a move up to mid-range or the high end of maintenance plateaus for P1 and K soil test levels might be more profitable for corn and soybean production that targeting for the maintenance of P and K test levels at or just above the respective average (60 to 90% sufficient) Critical Level for each of these nutrients? 5

5 Agronomy 375 Key - Exam I October 2, pts 1. A producer can monitor input use efficiency by following the cost of production per bushel. Optimum input mix efficiency and maximum profit are associated with the position where cost per bushel is minimized. A producer is justified in adding further inputs as long as the cost per bushel continues downward in response. Optimum input mix is attained when inputs are added up to the point where marginal cost equals marginal revenue ( the last dollar of input cost returns only one dollar in additional revenue). 4 pts 2. Yes. Over the long run, a producer who is watching their input costs as noted in question 1 above, will be adding optimal input levels and avoiding excessive input levels or abusive practices which may prove harmful to the environment or to the long term productive potential of the soil. In addition, effective management of productive fields leaves other, less productive areas out of production and in alternative uses for which they are better suited (e.g. pasture, wildlife refuge, etc.). Example: efficient utilization of applied N fertilizer (as influenced by the timing and rate of application) also means low levels of nitrate leaching into the groundwater. In addition, other less productive acres which would require greater inputs per bushel produced, may then be left out of production. 12 pts pt. GPS is an acronym for "Global Position System" and commonly refers to the use of satellites and differential correction signals to provide time-stamped information pertaining to latitude, longitude and elevation. Varying levels of precision are available. 1 pt. RTK is an acronym for Real Time Kinematic indicating a level of GPS repeatable and pass to pass precision which is sub-inch. This level of precision is commonly used in applications such as auto-steer which require precise location to be continuously calculated. 2 pts. GIS is an acronym for "Geographic Information System" and refers to the acquisition and GPS based spatial mapping of a wide range of data. 2 pts. VRT is an acronym for "Variable Rate Technology" and refers to the application of variable rates of a crop input as determined by position relative to accurately-mapped spatial data (such as soil type boundaries or yield history within a field). 6 pts. Example: GPS determines the position of a combine as it moves through a field, RTK auto -steer navigates the combine through the field with sub-inch accuracy. GIS monitors and maps yield data relative to discrete positions within the field. VRT can be used to vary the amount of maintenance P or K fertilizer applied site-specifically within the field to reflect differing historical yield levels as mapped. 8 pts 4. a) Soil type (as denoted on soils maps and visually by color, texture, slope, drainage). b) Prior management Records are used to indicate prior management differences within a field. These might include differences in yield, prior ownership, crop rotation, etc. Once a field's yield and soil test level histories are established, areas of similarly productive soils with a history of equivalent soil test levels and yields can be consolidated for representative sampling as units or unique management zones). 5 pts 5. a) 8 inches 2 pts. b) sq. root of [43560 sq. ft. X 3 acres in each grid unit] = a grid spacing of ft. 4 pts 6. a) 15 4 pts b) ( 15-9 ) ( 5 ) = (6) (5) = 30 pounds P / acre 4 pts 7. a) 75 + ( 2.5 X C.E.C.) = 75 + ( 2.5 X 16) = = pts b) (Critical Level 115 Soil Test Level 90 ) [ 1 + ( 0.05 X CEC 16 ) ] = 1

6 ( 25 ) [ 1.8] = 45 pounds K 2 0 / acre 3 pts 8. a) C. L Maintenance Range Width 15 = Maintenance Range Max 30 3 pts b) Maintenance Max 30 + Drawdown Range Width 10 = 40 3 pts c) Critical Level Maintenance Range Width 30 = Maintenance Max pts d) Maintenance Maximum Drawdown Range Width 20 = pts 9. a) A passive symptom is one in which the cause does not involve the physiology of the damaged plant. Examples: Hail damage removes leaf tissue. Insect feeding removes silk tissue from corn ears. An active symptom involves the physiology of the plant in symptom development. Examples: Tabled roots form as soil compaction presents resistance to penetration by roots. Corn brace roots grow together in response to the application of a growth regulating herbicide. 3 pts. 10. a) A primary symptom is the direct result of a cause. Examples: Hail damage remove leave tissue. Root feeding by Corn Rootworm larvae prunes roots. b) A secondary symptom is the indirect result of a cause. Examples: Corn leaves still in the whorl cut by hail stones and then can not unfurl properly so leaf twisting results as growth continues. Potassium deficiency symptoms appear on corn leaf margins where roots pruned by Corn Rootworm larvae are limited in their ability to take up potassium. 4 pts 11. The line transect method measures percent surface cover (by residue). The measurement is conducted by observing the percent of regularly spaced points (e.g. the foot interval marks on a measuring tape or evenly spaced knots on a knotted rope) which are in direct visual contact with surface residue on a line laid on the soil surface at a 45 degree angle to the previous crop's row direction. 9 pts. 12. a) Greater surface residue intercepts the impact of falling raindrops and protects soil particles from being dislodged. b) Greater surface residue serves as a barrier to slow water runoff and improve infiltration. c) Larger aggregates are maintained which are less vulnerable to being dislodged and moved by rainfall and runoff. d) Larger aggregates provide a barrier which slows runoff and increases infiltration. e) Greater soil structure is maintained beneath the no-till field as the effects of several structure building events accumulate (i.e. root growth and decomposition leaves channels in the soil, shrink/swell associated with soil wetting and drying leaves fissures, and earthworm activity leaves tunnels throughout the profile). Result is greater infiltration/internal drainage and less runoff. 2

7 8 pts 13. No-till systems will typically demonstrate higher bulk density (initial tillage lessens bulk density for the first few weeks of the season), lower temperature (insulating blanket of residue retains low soil temperature and residue reflects warming sunlight away), and higher moisture (greater infiltration and less evaporative loss under residue means wetter, cooler conditions) near the surface (where young roots are forming) vs. a conventionally-tilled system. All of these factors result in less total root growth and a more shallow placement of root growth in the no-till system. 8 pts 14. a) Erosion Control: Living (or dead) cover crop vegetation above ground and roots in the soil directly reduce soil dislodgement and movement by intercepting the impact of wind or water and/or acting as a barrier against water and soil movement. b) Economic value. Graze or bale the cover crop pre-knockdown (particularly where season length allows vigorous Fall and Spring growth). c) Nitrogen trap/catch crop. Captures and retains a portion of last seasons N in the field. d) Nitrogen fixation by legume cover crops can add N for use by next year s crop. e) Improved Soil Tilth/Structure & Soil and Water Conservation. Enhanced earthworm tunneling and added organic matter enhances aggregation, aeration, infiltration (less runoff as per above) and crop rooting depth (greater access to water and nutrition). f) Crop rotational yield improvement due to enhanced soil structure, improved weed, insect pest and disease suppression (crop rotation effect). g) If knockdown managed well soil dries more quickly in the spring allowing earlier access and planting. h) Weed suppression. 5 pts BONUS Targeting P and K soil fertility at or just above the Critical Level (Economic Goal) should provide sufficient P and K in most situations with normal levels of year to year variation in yield. However, in exceptionally productive management zones, yield may be consistently high across years (e.g. where there is good water holding capacity yet excellent soil drainage, no compaction so the root zone is deep, etc.). In such a situation the potential for factors other than P and K fertility to be most limiting to yield is reduced so a crop manager may indeed find economic response to higher than Critical Levels of P and K near the upper end of but still within the Maintenance Plateau. Similarly any shift in cropping systems technology (e.g. the introduction of drought tolerant genetic traits) which significantly lessens the potential of other cropping system variables to be primary limiting factors) may increase the potential frequency of P or K soil test level to become the most limiting factor. Well-designed, multi-year, randomized, replicated field testing is in order such situations in order to test the potential for economic response to higher soil test levels of P or K. 3