Contact Info, Current Projects, and Recent Publications

Education:

1970-1974      B.A. Biology, SUNY at Buffalo, NY

1980-1981      Post graduate studies at Univ. of Tennessee, Knoxville, TN 

1981-1987      M.S. and PhD/Soils and Soil Physics. Cornell University, Ithaca, NY

Professional Experience:

2000-present  Soil Scientist USDA-ARS, Alternate Crops and Systems Laboratory, Beltsville, MD.

1996-2000      Soil Scientist USDA-ARS, Remote Sensing and Modeling Laboratory, Beltsville, MD. 

1991-1997      Soil Scientist USDA-ARS, Systems Research Laboratory, Beltsville, MD.

1989-1991      Post-Doctoral Research Associate. USDA-ARS Water Quality Management Lab, Durant.

1987-1989      Post-Doctoral Research Associate with Utah State Univ and Senior Research Associate with Cornell University. Work location was in Nepal as a visiting scientist at the Institute of Agriculture and Animal Science and consultant in an irrigation management project.

1981-1987      Graduate Research Assistant. Dept. of Agronomy, Cornell University, Ithaca, NY

1974-1978      Peace Corps Volunteer - Nepal

1996-present Associate editor, Agronomy Journal. 

Research Interests:

The CRIS project I work in is titled "Integrated Crop Simulators for Resource Management," and I provide leadership for research directed toward understanding the fundamentals of physical and biological soil processes and their interaction over a range of scales, from the plant to the field. By training I am a soil physicist and a biologist which leads to my interest in biophysics. I am interested in how plants and their environment interact and how to quantify that interaction using mathematical relationships. I am interested in plant-soil relationships at both the plant and field scale. Much of my work is directed toward developing plant and soil simulation models that growers can use to assist in management decisions. Another aspect of my work is it study spatial relationships among soil and landscape properties such as soil texture and soil surface curvature, and crop growth and yield. I am interested in learning how one can use crop models and spatial statistics to better map soil hydraulic properties from sparse measurements.

Publications 1992-present.

1.    Timlin, D.J., G.C. Heathman, and L.R. Ahuja. 1992. Solute leaching in crop row vs. interrow zones. Soil Sci. Soc. Am. J. 56:384-392 

2.    Pachepsky, Ya., D. Timlin, B. Acock, H. Lemmon, and A. Trent. 1992. 2DSOIL A new simulator of soil and root processes. (version 02), Systems Research Laboratory Publication #2, Beltsville, MD.

3.    Timlin, D.J., L.R. Ahuja, G.C. Heathman. 1993. Preferential transport of a non-adsorbed solute: Field measurements. p 386-387 In Agricultural Research to Protect Water Quality, Minneapolis, MN, 21-24 February, 1993. Soil and Water Conservation Soc.

4.    Pachepsky, Ya., B. Acock, H. Lemmon, D. Timlin, A. Trent. 1993. 2DSOIL- A new soil-plant simulator to assess the influence of management practices on water quality. p 388-389 In Agricultural Research to Protect Water Quality, Minneapolis, MN, 21-24 February, 1993. Soil and Water Conservation Soc.

5.    Lemmon, H.E., N. Chuk, V. ,Reddy, B., Acock, Y. Pachepsky, D., Timlin, M. Van Venuchten, J, Simunek, T., Vogel. 1994. Sigma+ An advanced cotton management system. Proceedings of the Cotton Beltway Conference, Meeting held January 5?8. Pp. 589. - conference proceedings.

6.    Timlin, D.J., L.R. Ahuja and M.D. Ankeny. 1994. A comparison of three field methods to calculate apparent macropore conductivity. Soil Sci. Soc. Am. J. 58:278-284.

7.    Heathman, G.C., L.R. Ahuja, D.J. Timlin. 1994. Surface aggregates and macropore effects on chemical transport in soil under rainfall. Soil Sci. Soc. Am. J. 59:990-997.

8.    Timlin, D.J., Pachepsky. Ya, Acock, B., Lemon, H. and Tent, A. 1995. 2DSOIL - A Two-Dimensional Modular Simulator of Soil and Root Processes. In: Proceedings of the 1995 Workshop on Computer Applications in Water Management. 23 to 25 May, 1995. Colorado Water Resources Research Institute Information Series No. 79. Pg 174-178.

9.    Reddy, V.R., B. Acock, and D. J. Timlin. 1995. Role of crop models in technology transfer and input optimization. In V.R. Reddy and T.Y. Reddy (ed.) Modular Crop Growth Models, Kalyani publishers, New Delhi, India.

10.  Timlin, D. J. and Ya. Pachepsky. 1996. Comparison of three methods to obtain the apparent dielectric constant from time domain reflectometry wave traces. Sci. Soc. Am. J. 60:970-977

11.  Pachepsky, Y., D.J. Timlin, and G. Varallyay. 1996. Artificial neural networks to estimate soil water retention from readily available soil data. Soil Sci. Soc. Am. J. 60:727-733.

12.  Timlin, D.J., Ya. Pachepsky, and B. Acock. 1996. A design for a modular, generic soil simulator to interface with plant models. Agronomy J. 88:162-169.

13.  Timlin, D.J., Ya. Pachepsky, B. Acock, and F. Whisler. 1996. Indirect estimation of soil hydraulic properties to predict soybean yield using GLYCIM. Agric. Sys. 52:331-353.

14.  Caldwell, R.M., Y. Pachepsky, and D. Timlin. 1996. Current research status on growth modeling in intercropping. Pg. 617-635. In O. Ito et al. (ed) Roots and Nitrogen in Cropping Systems of the semi-arid tropics. Proceedings of the International Workshop: Dynamics of Roots and Nitrogen in Cropping Systems of the Semi-Arid Tropics. 21-25 Nov 1994. International Crops Research Institute of the Semi-Arid Tropics, Patancheru, Andhra Pradesh, India.

15.  Pachepsky, Ya. and D.J. Timlin. 1996. Infiltration into layered soil covered with a depositional seal. J. Agrophysics. 10:21-30

16.  Timlin, D. J., R.D. Williams and L.R. Ahuja. 1996. Methods to estimate soil hydraulic parameters for regional-scale applications of mechanistic models. p.185-203. In D. Corwin and K. Loage (ed.) Applications of GIS to the modeling of non-point source pollutants in the vadose zone. ASA Special publication ASA, CSSA, and SSSA, Madison, WI.

17.  Timlin, D.j., Ya. Pachepsky, And V.R. Reddy. 1996. Infiltration and water uptake in row and interrow positions in soybean (Glycine Max L.) p.335-343. In Proc. of the International Agricultural Engineering Conference, Pune, India, 9-12 December, 1996.

18.  Timlin, D.J. and Ya. Pachepsky. 1997. A modular soil and root process simulator. Ecological Modeling. 94:67-80.

19.  Timlin, D. J. L.R. Ahuja, and G.C. Heathman. 1998. Preferential transport of a bromide tracer applied in a pulse of ponded water. J. Env. Qual. 27:505-514  

20.  Timlin, D. J., Ya. Pachepsky, V. A. Snyder, and R.B. Bryant. 1998. Spatial and temporal variability of corn grain yield on a hill slope. Soil Sci. Soc. Am. J. 62:764-773

21.  Pachepsky, Ya. and D. Timlin. 1998. Water transport in soils as a fractal media. J. of Hydr. 204:98-107.

22.  Pachepsky, Ya. And D. Timlin. 1998. Generating spatially correlated fields with a genetic algorithm. Computers and Geosciences 24(8):765-769. 

23.  Timlin, D.J. and Ya. Pachepsky. 1998. Measurement of unsaturated soil hydraulic conductivities using a ceramic cup tensiometer. Soil Sci. 163(8):625-635

24.  Timlin, D.J., Ya. Pachepsky, V.A. Snyder, and R.B. Bryant. 1998. Soil surface curvature and the spatial and temporal variability of corn grain yield on a hillslope. In P.C. Robert, R.H. Rust, and W.E. Larson (eds). Precision Agriculture: Proceedings of the 4th International Conference. Pp.203-214. St. Paul, Minnesota, July 19-22.

25.  Timlin, D.J., L.R. Ahuja, Ya Pachepsky, R.D. Williams, D. Gimenez, and W. J. Rawls. Use of Brooks-corey Pore Size Distribution Index to Improve Estimates of Saturated Conductivity from Effective Porosity. Characterization and Measurement of the hydraulic properties of unsaturated porous media. Univ. of Calif. Riverside. 1999. v. 2. p 1029-1036.

26.  Timlin, D.J., L.R. Ahuja, Ya. Pachepsky, R.D. Williams, D. Gimenez, and W. Rawls. 1999. Use of Brooks-Corey parameters to improve estimates of saturated hydraulic conductivity from effective porosity. Soil Sci. Soc. Am. J. 63:1086-1092.

27.  Reddy, V.R., D.J. Timlin, Ya. Pachepsky. 1999. Quantitative description of plant density effects on branching and light interception in soybean. Biotronics 28:73-85.

28.  Pachepsky, YA; Rawls, WJ; Timlin, DJ. 1999. The current status of pedotransfer functions: Their accuracy, reliability, and utility in field- and regional-scale modeling. In: Assessment of Non-point Source Pollution in the Vadose Zone, 108: 223-234 1999.

29.  Pachepsky, Ya, D.J. Timlin, and L.R. Ahuja. 1999. Estimating saturated hydraulic conductivity using soil retention data and neural networks. Soil Science. 164:552-560

30.  Timlin, D.J., J.L. Starr, R.E. Cady, and T.J. Nicholson. 2000. Comparison of Estimated Ground-Water Recharge Using Different Temporal Scales of Field Data. NUREG/CR-6653, U.S. Nuclear Regulatory Commission, Washington, DC

31.  Pachepsky, Ya., D. Benson, and D.J. Timlin. 2001. Transport of water and solutes in soil as in porous fractal media. p 51-75. In H.M. Selim and D.L. Sparks (ed.) Physical and Chemical Processes of Water and Solute Transport/Retention in Soil. ASA Spec. Pub. 56. ASA, CSSA, and SSSA, Madison, WI.

32.  Pachepsky, Ya, W.J. Rawls, and D.J. Timlin. 2000. A one-parameter relationship between unsaturated hydraulic conductivity and water retention. Soil Science. 165:911-919.

33.  Timlin, D.J., Ya. Pachepsky, F.D. Whisler and V.R. Reddy. 2000. Automated parameter estimation for the soybean crop model GLYCIM. Remote Sensing and Modeling Lab Special Publication #11.

34.  Timlin, D.J. Ya. Pachepsky, and M.Th. van Genuchten. 2001. 2DSOIL, A modular simulator of soil and root processes. Ver 0.3. USDA-ARS Alternate Crops and Systems Laboratory Special Publication #1.

35.  Timlin, D.J., Ya. Pachepsky, C.L. Walthall, and S.E. Loechel. 2001. The use of a water budget model and yield maps to characterize water availability in a landscape. Soil and Tillage 58:219-231

36.  Timlin, D.J., Ya. Pachepsky, V. A. Snyder, and R. B. Bryant. 2001. Water budget approach to quantify corn grain yields under variable rooting depths. Soil Sci. Soc. Am. J. 65:1219-1226.

37.  Timlin, D.J., Ya. Pachepsky, B.A. Acock, J. Šimunek, G. Flerchinger, and F. Whisler. 2001. Error analysis of soil temperature simulations using measured and estimated hourly weather data with 2DSOIL. (Agric. Sys. In publication, accepted Jun, 2001)

38.  Timlin, D.J., Ya Pachepsky, and V.R. Reddy. 2001. Soil water dynamics in row and interrow positions in soybean (Glycine max L.) (Accepted Aug. 2001).

39.  Pachepsky, Ya, D.J. Timlin, W.J. Rawls. 2001 Soil water retention as related to topographic variables. Soil Sci. Soc. of Am. J. (Soil Sci. Soc. Am. J. 65:In press).

40.  Timlin, D.J. and Ya. Pachepsky. 2001. Infiltration Measurement Using a Vertical Time-Domain Reflectometry Probe and a Reflection Simulation Model. Soil Science. (Accepted Sept. 2001 )

41.  Timlin, D.J., Ya. Pachepsky, F.D. Whisler, and V.R. Reddy. 2001. Experience with on-farm applications of GLYCIM/GUICS. In. Agricultural System Models in Field Research and Technology Transfer (accepted Sept, 2001).

42.  Timlin, D.J., J.L. Starr. R. Cady, T.J. Nicholson. 2001. Field Studies for Estimating Uncertainties in Ground-Water Recharge Using Near-Continuous Piezometer Data.NUREG/CR-6729, U.S. Nuclear Regulatory Commission, Washington, DC.

43.  Walthall, C. L., Y. Pachepsky, W. P. Dulaney, D. J. Timlin, and C. S. T. Daughtry. 2001. Using spatial variance information from remotely sensed imagery to map crop foliage density. In: Proceedings of the Third International Conference on Geospatial Information in Ariculture and Forestry, Denver, Colorado, 5 -7 November 2001. - conference proceedings.

44.  Starr, J.L., and D.J. Timlin. 2001. Estimating Preferential Infiltration and Redistribution from Real-time Measurements of Soil Water Content. P. 97-100. In Preferential Flow - Water Movement and Chemical Transport in The Environment. Proc. Int. Symp., 2nd, Honolulu, HA. 3-5 Jan. 2001. ASAE, St. Joseph, MI.

45.  Timlin, D.J., Walthall, C. L., Y. Pachepsky, W. P. Dulaney, and C. S. T. Daughtry. 2001. Spatial Regression of Crop Parameters with Airborne Spectral Imagery In: Proceedings of the Third International Conference on Geospatial Information in Ariculture and Forestry, Denver, Colorado, 5 -7 November 2001. - conference proceedings.