Robert Grisso

A Stress State Transducer for Soil

ABSTRACT Atransducer was developed that measured normal pressures in six predetermined directions to provide data for mathematically determining the complete stress state in soil. The stress state transducer was evaluated under hydrostatic loading in both a sand and a clay. All six sensing elements registered within 6% of the applied pressure.

A Soil-Tool Model Based on Limit Equilibrium Analysis

ABSTRACT A mathematical model for predicting the behavior of narrow tillage tools in soils is based on a limit equilibrium analysis. Pertinent soil, tool and interface parameters influencing the tool performance have been identified and incorporated in the model. A comparison of predicted and experimental results is also included. Mathematical models based on emperical as well as semi-emperical methods have been developed to describe the soil-tillage tool interaction (Payne, 1956; Hettiaratchi and Reece, 1967; Hettiaratchi et al., 1966; Osman, 1964; Godwin and Spoor, 1977; McKyes, 1978; Desai et al., 1981). Even though the soil-tool interaction problem is three dimensional in nature, a majority of the models available are based on two-dimensional consideration (Hettiaratchi et al., 1966; Osman, 1964; Payne, 1956). In recent years some progress has been made toward the development of three dimensional models (Hettiaratchi and Reece, 1967; Godwin and Spoor, 1977; McKyes, 1978). However, most of these models are complex, and a sound mathematical background is essential to utilize them. Thus the need exists for more general and less complex models capable of predicting tillage-tool behavior in soils. Unlike costly experimental procedures, availability of such models would permit designers as well as researchers to develop with minimum effort a clear understanding of soil-tool interaction through parametric studies. Therefore, the overall objective of this study was to develop a generalized mathematical model and to examine its validity for predicting the tillage tool performance in soils..

Tillage Implement Forces Operating in Silty Clay Loam

Regression equations for draft forces of a tandem disk, chisel plow, and field cultivator were developed based upon travel speed and tillage depth. The effect of tillage depth on the draft of the tandem disk, chisel plow and field cultivator was observed to have more influence than travel speed.

ANALYSIS OF TRAFFIC PATTERNS AND YIELD MONITOR DATA FOR FIELD EFFICIENCY DETERMINATION

Field efficiency is an important criterion for determining the expected field capacity and, indirectly, for making important machinery management decisions. The data gathered with a yield monitor during harvest and a DGPS monitor during planting were used to provide time–motion studies of equipment and operator productivity. This study used spatial data gathered by a farmer to determine field performance of a combine and a planter. Five fields were used to compare results from soybean and corn production. Fields that are relatively flat with straight rows were contrasted with contoured fields with slopes up to 3 to 5%. Field efficiency, travel speeds, and unproductive time lapses were compared. When contour patterns were compared with the straight rows, field efficiency dropped on the contours by 10 and 20% for planting and harvesting, respectively. Average travel speeds were slower for contour patterns than straight rows by more than 1.6 km/h (1 mph). Although the histograms of the time lapses were very similar for contour and straight patterns, almost twice the number of time lapses was found with the contour pattern.

Tractor performance spreadsheet for radial tires

Abstract Lotus-compatible templates were revised from the Zoz (1987) spreadsheets. Performance of two-wheel-drive (2WD) and four-wheel-drive/mechanical-front-wheel-drive (4WD/MFWD) tractors were predicted on agricultural soils for radial tractor tires. Comparisons between the predicted and experimental results of 41 tractors using radial tractor tires showed fair agreement. The performance parameters used in the comparisons were wheel slip, drawbar pull and tractive efficiency. The percentage differences were calculated and the acceptable range was set at 20% difference. For wheel slip, 22 out of 41 tractors had percentage differences that fell within the acceptable range. The drawbar pull comparison showed that 35 out of the 41 tractors had percent differences within the acceptable range. The tractive efficiency comparison showed that 27 out of 33 tractors had percentage differences that fell within the 20% range. The predicted drawbar pull and tractive efficiency were higher than the experimental values in most cases of MFWD tractors. Because some input values for the spreadsheet such as available power, cone index and travel speed were not given in the source of data, the predicted results of tractor performance were not in close agreement to experimental results.

NORMALIZING CONE RESISTANCE VALUES BY CovARiANCE ANALYSIS

Measured cone index values were adjusted for soil water content and bulk density by normalizing their effects using a covariance analysis as described by Christensen et al. (1989). Cone indices adjusted by covariance analysis allowed the testing of tillage differences at a given depth and across depths. The procedure showed that double disking a Sharpsburg silty clay loam soil reduced the cone penetration resistance to 152 mm depth. The penetration resistance was similar in the deeper undisturbed zones. Unadjusted field measured cone indices showed differences in the deeper zones though no tillage was performed.

FIELD EFFICIENCY DETERMINATION USING TRAFFIC PATTERN INDICES

Field efficiency is an important criterion for determining field capacity during field operations and, indirectly, for making important machinery management decisions. Geographic location data gathered with a yield monitor during harvest and a data logger during planting were used to provide time-motion studies of equipment and operator productivity. This study used these spatial and temporal data to quantify field performance of a combine and a planter. Seven Nebraska fields were used to compare results from soybean and corn production systems. Fields that were relatively flat with straight rows were contrasted with contoured fields with slopes of 3% to 5%. Two unique traffic patterns in fields with a center pivot were compared. Four traffic pattern indices were developed and averaged across each field to indicate the steering behavior (or adjustments) made during field operations. Geo-referenced data were used to predict field efficiency for various traffic patterns. Of the four indices compared, the average steering angle (.) and its standard deviation had the strongest association with field efficiency with Pearson correlation coefficients of -0.654 and -0.664, respectively. The average steering angle for contoured traffic patterns were two to four times in magnitude that of straight- and gently curved-row traffic patterns. The steering angle index gave valuable information about field operating conditions but differences in data recording methods and operational characteristics imposed limitations on statistically appropriate comparison analyses.

Fuel Prediction for Specific Tractor Models

Generalized models for fuel consumption are useful for budget and management scenarios, but may not have the ability to compare fuel consumption for several potential tractor configurations such as turbocharging and air densification models. The objective of this article is to develop a method that uses the Nebraska Tractor Test Lab (NTTL) data for a specific tractor model to predict fuel consumption for full and partial loads and for reduced throttle conditions. Using these equations, the fuel savings can be predicted for different operating and loading conditions. This method is compared with the generalized model and actual NTTL fuel consumption data. The results showed that 88% of tractors had an improved prediction with the new methodology.

YIELD MONITOR ACCURACY: SUCCESSFUL FARMING MAGAZINE CASE STUDY

A joint project of the University of Nebraska and Successful Farming magazine observed the harvest operations of three corn farmers using yield–monitoring technology. Two farmers with level fields of high–yielding corn were asked to operate their combines at under–capacity (20–30% reduction in travel speed), over–capacity (20–30% increase in travel speed), and their typical travel speed. The other farmer was observed going up and down a 5–10% slope. The weight of harvested corn measured by the yield monitor was compared to a weigh wagon after each pass. The results showed that yield monitor calibration and combine operational characteristics play an important role in accurate yield monitor response.

Review of Models for Predicting Performance of Narrow Tillage Tool

ABSTRACT FOUR narrow tillage tool models are reviewed. Assumptions, capabilities and limitations associated with each model are discussed. Tillage tool performance under two different soil conditions have been predicted using the four models. Simulated results are compared with the experimental results.