David P. Shelton

Tillage, Residue and Erosion on Moderately Sloping Soils

ABSTRACT TILLAGE treatments leaving 20% or more of the soil surface covered with residue reduced soil erosion by at least 50% of that which occurred from a moldboard plow system. No-till had the least erosion and tended to have the lowest cumulative runoff. These results were based on rainfall simulation tests on six tillage treatments used on both 5 and 10% slopes in continuous corn production.

Soil Erosion from Tillage Systems Used in Soybean and Corn Residues

ABSTRACT RAINFALL simulation techniques were used to compare soil losses from various tillage systems used on plots where corn and soybeans had been grown the previous season. The two year study was conducted on a silty clay loam soil with a 5% slope and on a silt loam soil with a 10% slope. Five tillage treatments, ranging from a moldboard plow system to no-till, were evaluated for each residue at each site. Tillage and planting operations were conducted up-and-down hill on replicated plots. Total soil loss following 63.5 mm of rainfall applied during a 60 min period averaged more than 40% greater from the soybean residue plots than from the corn residue plots for equivalent tillage treatments on the 5% slope. For the 10% slope, the soil loss ranged from 50% to about 12 times greater for the soybean residue. Equivalent tillage treatments in soybean residue had about 40% less surface cover relative to corn residue, which contributed to the difference in soil erosion. Relationships between residue cover and soil loss showed that a 20% cover of either soybean or corn residue generally reduced soil loss by at least 50% of that which occurred from cleanly-tilled soils. Several tillage systems left more than a 20% cover in corn residue. Only no-till consistently left more than a 20% residue cover following soybeans..

Electronic Image Analysis of Crop Residue Cover on Soil

ABSTRACT CLASSIFICATION procedures for using both black-and-white and color imaging systems were developed and tested for determination of percent residue cover on the soil surface from video and slide images. A spectral analysis of the image components was used for determining applicable wavelengths and filters. Color imagery provided an acceptable replacement for manual visual procedures. Black-and-white imagery also worked when appropriate blocking filters were used.

Soil Erosion from Tillage and Planting SystemsUsed in Soybean Residue:Part II - Influences of Row Direction

A rainfall simulator was used to compare soil losses from various tillage and planting systems used in residue from soybeans which had been grown in both wide and narrow spaced rows the previous season. Upand-down hill tillage and planting treatments ranging from a double disk system to no-till planting were evaluated using replicated plots on a silt loam soil in the Nora Series having a 10% slope. Tillage and planting systems used in soybean residue from narrow spaced rows had soil erosion and soil erosion rates that were reduced by approximately SO% compared to the same systems used in residue from wide spaced soybeans. However, the reductions were significant only for the double disk tillage system. There was a trend for the start of runoff to be delayed and for residue cover, accumulated runoff, runoff rate, and sediment concentration to be reduced for tillage systems used in narrow row soybean residue compared to the same systems used in residue from wide spaced rows.

Development of a Storm Runoff Simulator: Part 2 – Water Output Control Device

Few studies have evaluated conservation buffers at field to buffer area ratios of 30:1 or greater. A storm runoff simulator is needed to better evaluate flow hydraulics, sediment trapping, and water quality benefits of field-scale conservation buffers. Based on an engineering analysis using MUSLE and the SCS Curve Number Method, it was determined that a simulator could be developed for a 1- × 9-m buffer plot, with input constraints of 7580-L stored water and 0.71 metric tons of soil. The objective of this study was to design, build, and test a prototype runoff simulator water output control device operating under gravity flow conditions. The control device regulates flow using a gear motor mounted on a rotary gate valve, and a feedback control system between a flow meter and the rotary valve. A time-compressed 10-yr, 2-h SCS design hydrograph with a 7.3-L s-1 peak flow rate was used to calibrate the flow control device for optimal performance with large changes in flow rate, and for repeatability with a variety of hydrograph shapes. When reproducing the compressed SCS hydrograph, the control device maintained comparable efficiencies among repetitions; with a 2% error between root mean square error and the total flow range. Hydrographs with step changes in flow rate, flow rate plateaus, multiple peaks, and flow rates up to 9.8 L s-1 could be simulated with comparable efficiencies and 4% to 6% error.

Development Of A Storm Runoff Simulator: Part 1 – Design Considerations

Evaluation of conservation buffers has relied primarily on small-scale plot (30 to 50 m2) studies with a limited range of buffer widths and field to buffer area ratios (BARs). Most studies used simulated runoff at steady flow rates. There is a need to evaluate conservation buffers installed at NRCS design widths and BARs to assess how well in-field buffers reduce nonpoint source pollution, especially for unsteady flow. The goal of this project is to develop a storm runoff simulator to distribute variable flow rates and contaminant concentrations across the upslope end of a buffer in a reproducible fashion. The simulator design should allow for easy transportation and adaptability to terrain and resource constraints found in the field. The SCS CN Method and the MUSLE were used to evaluate eight alternative combinations of BAR and buffer size. Buffer size ranged from 30 to 67.5 m2. Given the design constraints of less than 1 metric ton of soil per simulation, only a 1- × 9-m plot size met the design criteria. Based on realistic constraints of a 7580-L available water supply, the final design constraints included a 7.3-L s-1 peak flow rate and 0.71 tons of soil, for a 1- × 9-m plot, which allowed for BARs up to 49:1.

IMPROVED SOIL MIXING AND DELIVERY SYSTEM FOR A STORM RUNOFF SIMULATOR

An earlier version of a storm runoff simulator to test conservation buffers reproduced target hydrographs and sedigraphs using uniform, fine sand; however, it was unable to uniformly mix and deliver native sediment. The objectives of this work reported were to create a method to process native agricultural sediment, mix a uniform sediment slurry at a target concentration, and create a control system that will deliver the slurry in varying flow rates corresponding to a target sedigraph. Eroded silty clay (14% sand) was scraped, dried, and processed with a hammer mill. A sand (93% sand) and loam (44% sand) were dried and screened for organic debris and large clods. Each soil type was mixed by an axial flow impeller in an 1890-L cone-bottom tank. Recirculation through a trash pump was used to further break down aggregates and maintain a uniform sediment concentration in the tank. A V-Port ball valve under pressurized flow was used to achieve outflow control. The sediment mixing system was capable of producing concentrations within 3.3% of the target concentration with a maximum test concentration of 0.294 kg L -1 with the silty clay soil. Simulated hydrographs had a Nash Sutcliffe Efficiency of 0.998, a Root Mean Square Error of 0.06 L s -1 , and a peak flow rate within 1% of the target flow. Simulated sedigraphs with silty clay had similar performance. Neither the sandy soil, nor the loam, were successfully delivered through the system to match target sedigraphs. The sand could not be uniformly mixed in the tank, but the loam was uniformly mixed to the target concentration.

Development of a Storm Runoff Simulator: Part 3 – Sediment Mixing Device

Runoff simulators used in plot research have not effectively represented a natural hydrograph and sediment graph. Therefore, an improved runoff simulator is needed to better evaluate the performance of conservation buffers and similar practices. The objective of this study was to design, build, and test a prototype sediment mixing device that could be incorporated into the final design of a storm runoff simulator. Based on an engineering analysis, the simulator design constraints were a maximum water volume of 7580 L, a peak flow rate of 7.3 L s-1, a maximum sediment load of 882 kg, and peak sediment rate of 1.15 kg s-1. The sediment mixing device consists of an impeller agitated mixing tank to create a homogeneous slurry of fine silica sand and water. Slurry outflow is measured and controlled by an output control system operating under gravity flow conditions. A time-compressed 5-yr, 2-h SCS design storm with an eroded sediment mass of 442 kg and a peak sediment rate of 1.3 kg s-1 was used to verify performance. When reproducing the design sediment graph using a slurry concentration of 0.30 kg L-1 comparable efficiencies among repetitions were maintained; with root mean square error (RMSE) representing less than 4% error between the RMSE and the peak flow or sediment rate. Peak sediment rates were within 7% of the target rate. The prototype sediment delivery system uses fine silica sand to represent clay and silt sized particles, and is capable of producing varying sediment rates that match a design sediment graph.

Reduced Nocturnal Temperatures in a Swine Nursery—A Modified Regimen

ABSTRACT THE influences on energy utilization and animal performance of a modified reduced nocturnal room air temperature management regimen in a swine nursery building were evaluated with four cold-weather trials using pigs weaned at three to four weeks of age. Reducing nighttime room air temperatures by as much as 5.9 C° beginning one week post-weaning resulted in a total energy savings of 41 MJ per weaned pig and utility cost savings of over 15% compared to a control temperature treatment which followed current recommendations. Nursery pigs subjected to reduced nocturnal temperatures consumed more feed per day (P<0.001) and gained more mass per day (P<0.06), with similar feed conversion efficiencies and mortality rates.

Variable Base Heating Degree-Day Data

ABSTRACT HEATING degree-day (HDD) data are often used to estimate annual fuel energy requirements for heating buildings. Commonly, a base temperature of 18.3°C (65°F) is used for calculating HDD. This fixed-base data is generally not appropriate for structures housing livestock since the balance or base temperature of the structure can vary significantly from 18.3°C. A simplified technique, using fitted-curve equations, has been developed to estimate average annual heating degree-days as a function of base temperature and location. This paper presents the method of calculation and specific equations for 70 cities in the United States. In addition, generalized heating degree-day equations for 25 states are presented and discussed.