VTechWorks staff will be away for the Thanksgiving holiday beginning at noon on Wednesday, November 27, through Friday, November 29. We will resume normal operations on Monday, December 2. Thank you for your patience.

Browsing by Author "Lillard, James H."

Now showing 1 - 6 of 6
  • Thumbnail Image
    Annual Report – Research in Soil and Water Conservation
    Lillard, James H. (1937)
    Second annual report for the soil and water conservation research project.
  • Thumbnail Image
    Design factors and operational requirements of irrigating burley tobacco
    Jones, J. Nick (Virginia Tech, 1954-12-05)
    This investigation of design factors and operational requirements for irrigating burley tobacco was conducted on a system of irrigation control plots located on the Smithfield farm of the Virginia Agricultural Experiment Station.
  • Thumbnail Image
    Hydrologic aspects of no-tillage versus conventional tillage systems for corn production
    Shanholtz, Vernon O.; Lillard, James H. (Water Resources Research Center, Virginia Polytechnic Institute, 1968)
    For many years one of the goals of tillage research at Virginia Polytechnic Institute has been to develop a system which (a) reduces the amount of tillage required, (b) maintains an open-sail structure conducive to good rainfall intake and storage, and ( c) makes more beneficial use of the residues of preceding crops for minimizing evaporation, soil erosion and runoff losses. From these investigations evolved the no-tillage system. With this system the crop is planted directly into a chemically killed sod or crop residue with no prior mechanical seedbed preparation, thereby utilizing vegetation from the preceding crop for surface mulch.
  • Thumbnail Image
    Progress Report – Soil and Water Conservation Investigations
    Lillard, James H.; Rogers, Howard T. (1939)
    Summary report of the scope and progress of cooperative investigations in soil and water conservation.
  • Thumbnail Image
    The relation of subsoiling, deep lime and deep phosphate application to the yields of corn, peanuts, and alfalfa in Virginia
    Stivers, Russell K.; Lillard, James H.; Jones, G. D.; Allison, Allen H. (Virginia Agricultural Experiment Station, 1956-03)
    Subsoiling has been practiced to a limited extent in some areas for many years. The practice may have promise of raising yields on certain Virginia soils
  • Thumbnail Image
    A soil water model for two contrasting tillage systems
    Shanholtz, Vernon O.; Lillard, James H. (Water Resources Research Center, Virginia Polytechnic Institute, 1970)
    Techniques were developed to simulate the soil-plant environment as a semi-dynamic hydrologic system. Exponential expressions were found to give reasonable estimates of soil evaporation prior to corn plant emergence. A family of non-linear curves were used to estimate evapotranspiration after corn plant emergence. These curves assumed that pan evaporation was the integrated result of atmospheric demands and was therefore defined as the potential condition. Precipitation excess was estimated from an exponential expression that was developed by Holtan45 from the 'total water storage capacity in the Ap or A soil horizon. Corn plant heights were simulated with a 2-part non-dimensional exponential relationship. Rainfall interception by the corn plant canopy was assumed to be a function of rainfall, plant height, and density of cover with the maximum allowable quantity at full tassel limited to 0.03 inch per storm per 15,000 plants. Vertical water movement through the soil was assumed to be related to its saturated hydraulic conductivity. The soil profile was subdivided into seven zones with the first zone terminating at the bottom of the Ap or A horizon and the seventh zone terminating at maximum root depth. Intermediate zones· were arbitrarily spaced at 6 and 12 inch intervals. The potential water holding capacity of each zone was further categorized as free water and plant available water. All recharge of the system took place in zone one. Subsequent recharge of lower depths or zones were allowed when free water existed in the zone immediately above. All aspects of the model were programmed in the Fortran language for an IBM 360 Computer. Each logical segment of the model was sub-routined to allow minimum effort for changes and/or modification. A comparison of simulated with observed data indicates very good agreement. With few exceptions, the simulated results were well within sampling variation.