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Ecological Intensification of Irrigated Corn and Soybean Systems

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Ecological Intensification of Irrigated Corn and Soybean Systems

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    1. Ecological Intensification of Irrigated Corn and Soybean Systems

    2. Definitions, Concepts, Considerations

    3. Crop Yield Potential (Yp) What is it? Theoretically achievable yield solely determined by genetic characteristics and climate (solar radiation, temperature). How to measure it? (a) Calculated from components of yield and radiation use efficiency. (b) Estimated by crop simulation models. How to achieve it? Fully-controlled, small-scale experiment to eliminate all biotic and abiotic stresses (water, nutrients, pests). How to increase it? (a) Breeding/germplasm improvement (b) Management: optimization of planting date in relation to variation in Yp due to the seasonal pattern of radiation and temperature.

    4. Variability of Crop Yield Potential

    5. Variability of Crop Yield Potential

    6. Attainable Crop Yield Potential (Ya) What is it? Yield that can be achieved by minimizing abiotic and biotic stresses through the best available technology at a given site in a typical production field. How to measure it? (a) Yield achieved in high-quality research experiments. (b) Yield achieved by yield contest winners. How to achieve it? Optimize all soil and crop management to achieve high use efficiencies of solar radiation, water and nutrients. Minimize yield losses due to insects, diseases, weeds. How to increase it? (a) Improve soil quality (gradual process). (b) Improve crop management (learning process)

    7. General Relationship Between: Yield and Inputs + Management

    8. Why is it Important to Raise Yield Potential?

    9. Yield Potential, Actual Yield, Profit and Resource Use Efficiency

    10. Yield Potential, Actual Yield, Profit and Resource Use Efficiency

    11. Yield Potential, Actual Yield, Profit and Resource Use Efficiency

    12. Yield Potential, Actual Yield, Profit and Resource Use Efficiency

    13. Yield Potential, Actual Yield, Profit and Resource Use Efficiency

    14. Yield Potential, Actual Yield, Profit and Resource Use Efficiency

    15. Why do we Need to Conduct Research on Understanding High Yields?

    16. Average vs. Attainable Corn Yields

    17. Average vs. Attainable Soybean Yields

    18. Average vs. Attainable Corn Yields

    19. Average vs. Attainable Soybean Yields

    20. How Does Soil Productivity Affect the Attainable Yield Potential?

    21. What Causes the Variability of Yield in Relation to Inputs and Management?

    22. Environmental Issues: Nitrate

    23. Environmental Issues: Nitrate

    24. Environmental Issues: C Sequestration

    25. Environmental Issues: C Sequestration

    26. Environmental Issues: N2O Emission Typical N2O emission from agricultural land: 1 to 2 kg N2O/ha per year less than 1% of N applied Median N2O emission (% of N applied): Anhydrous ammonia 1.63% (range: 0.9-6.8) Ammonium nitrate 0.40% (range: 0.04-1.7) Ammonium sulfate (chloride) 0.15% (range: 0.02-1.7) Urea 0.11% (range: 0.01-0.6) Nitrate 0.05% (range: 0.01-1.8)

    27. Global N fertilizer use (1999) Million t N % World: Total N 83.0 100 Urea 39.6 48 Ammonium nitrate 7.0 8 Anhydrous ammonia 4.5 5 Liquid N 4.2 5 Other straight N 14.8 18 Compound N 12.9 16 % of global USA: Total N 11.3 100 14 Urea 1.8 16 5 Ammonium nitrate 0.6 5 9 Anhydrous ammonia 3.6 32 80 Liquid N 2.8 25 67 Other straight N 0.3 3 2 Compound N 2.2 19 17

    28. Kellogg Station, Michigan (1991-99)

    29. What Do We Know About Growing Corn at Attainable Yield Potential Levels? Yield contest winners: Continuous corn system (no rotation!) Deep soils with soil fertility built up to very high levels. Deep tillage (12-14). High plant density (41,000 to 44,000 plants/acre). Slow planting speed (2 mph); accurate plant spacing, less than 2% skips. P, and K fertilizer inputs exceed average recommendations. Careful N management: Fall application for residue breakdown, narrow band pre-plant N application (10 apart), starter fertilizer, sidedressing. Frequent scouting and excellent pest control.

    30. What Do We Know About Growing Corn at Attainable Yield Potential Levels? Knowledge gaps: Basic scientific understanding of yield-determining processes and how they are affected by management. Solid scientific basis for efficient extrapolation to other locations (avoid trial and error). Knowledge of how to design optimal systems managed at 70-80% of the yield potential. Lack of studies that integrate productivity, profitability, and environmental consequences of high yield systems.

    31. Research at UNL

    32. Objectives Quantify the yield potential of irrigated corn and soybean. Understand the physiological processes determining it. Identify cost-effective and environmentally friendly crop management practices to achieve irrigated corn and soybean yields that approach potential levels. Determine how changes in soil quality affect the ability to achieve yields that approach yield potential levels. Quantify the energy use efficiency, soil C-sequestration and net radiative forcing potential of intensive corn and soybean management systems.

    33. Ecological Intensification Project: Examples of the Questions Addressed What is the yield and biomass potential of soybean and corn under irrigated conditions? How much do current photosynthesis and stored carbohydrate stalk reserves contribute to grain yield at high yield levels? Can we increase radiation and N use efficiency as we move yields up from present average yields to attainable yield levels? What are the nutrient requirements to achieve genetic yield potential and how do they change with the yield level? Do we need to increase soil quality to achieve optimal nutrient- and water-use efficiency at yield potential levels? How much? What are the environmental consequences (nitrate loss, N2 emission, energy consumption, etc.) of high input systems required for achieving yields that approach yield potential levels? What is the C-sequestration and net global warming potential of irrigated corn systems?

    34. Key Investigators

    35. Experimental Details: Lincoln, NE

    36. Experimental Design

    37. Fertilizer Program (Corn)

    38. Corn: Grain Yield 1999

    39. Corn: N uptake 1999

    40. Corn: P uptake 1999

    41. Corn: K uptake 1999

    42. Nutrient Uptake Requirements

    45. Corn: Total Biomass 2000

    46. Corn: Grain Yield 2000

    47. Corn: N uptake 2000

    48. Corn: Biomass Dynamics

    49. Possible Causes of Lower Attainable Yield in 2000 versus 1999? Late-season high (night) temperatures causing increased maintenance respiration and shorter grain filling period? Over-expression of vegetative biomass growth in relation to the actual yield potential? Non-linear relationship between leaf-N, respiration rate, and temperature? Mild water stress due to high vapor pressure deficit or imperfect irrigation? Early insect damage? Subtle yield losses from undetected diseases?

    50. Growth and Development

    51. Average Daily Temperature

    52. Simulated Daily Crop Maintenance Respiration Rate

    53. Nitrogen Use Efficiency: 1999

    54. Nitrogen Use Efficiencies: 2000

    55. Nitrogen Use Efficiency: Corn 1999

    56. Nitrogen Use Efficiency: 2000

    58. Crop Residue C After 2000 Harvest

    59. Soil CO2 flux for 37,000 plants per acre

    61. Conclusions

    62. Some Challenges Plant physiology & crop modeling: better understanding of processes governing fluctuation of yield potential in relation to climate and management. Role of non-structural carbohydrates for grain filling? Quantitative estimates of root biomass and exudates. High N2O losses: how to improve N management in combination with water management? Optimal timing and form of N? Use real-time N management? Disease control at high yield levels. Hypothesis: maximum profit and enhanced environmental quality are not mutually exclusive in high yield systems.

    63. Key References Broadbent, F.E., and A.B. Carlton. 1978. Field trials with isotopically labeled nitrogen fertilizer. p. 1-41. In Nitrogen in the environment. Vol. 1. Academic Press, New York. Cassman, K.G. 1999. Ecological intensification of cereal production systems: Yield potential, soil quality, and precision agriculture. Proc. Natl. Academy of Science 96:5952-5959. de Witt, C.T. 1992. Resource use efficiency in Agriculture. Agric. Systems 40:125-151. Duvick, D.N., and K.G. Cassman. 1999. Post-green revolution trends in yield potential of temperate maize in the North-Central United States. Crop Sci. 39:1622-1630. Gifford, R.M. and L.T. Evans. 1981. Photosynthesis, carbon partitioning, and yield. Ann. Res. Plant Physiol. 32:485-509. Greenwood, D.J., G. Lemaire, G. Gosse, P. Cruz, A. Draycott, and J.J. Neetson. 1990. Decline in percentage N of C3 and C4 crops with increasing plant mass. Ann. Bot. 66:425-436. Loomis, R.S., and J.S. Amthor. 1999. Yield potential, plant assimilatory capacity, and metabolic efficiencies. Crop Sci. 39:1584-1596. Specht, J.E., D.J. Hume, and S.V. Kumudini. 1999. Soybean yield potential - a genetic and physiological perspective. Crop Sci. 39:1560-1570. Sinclair, T.R., and T. Horie. 1989. Leaf nitrogen, photosynthesis, and crop radiation use efficiency: a review. Crop Sci. 29:90-98.

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