Larry G. Wells

Crop yield response to precision deep tillage

Experimental precision deep tillage was applied at three sites in central Kentucky with relatively well-drained silt loam soils in no-till crop production. Fields were divided into 0.4 ha (1 ac) grid cells using DGPS mapping. Assessment of soil compaction by machinery traffic was made using multiple soil cone penetrometer measurements and expressed as cone index (CI). Corn, wheat, and soybean yields were depressed in grid cells with CIavg > 1.5 MPa (218 psi) prior to application of tillage treatments at sites 1 and 3, whereas at site 2, where most of the highest average CI values ranged from 1.44 to 1.49 MPa (209 to 216 psi), the opposite was true. In general, deep tillage resulted in yield improvement in compacted grid cells relative to those receiving no deep tillage; however, differences were significant at the 10% level in only two of six instances. Cells tilled to 40 cm generally had higher yields than cells tilled only to the depth at which CIavg > 1.5 MPa (218 psi) (precision deep tillage) at sites 1 and 3. However, the opposite was true for double-crop soybean subjected to limited rainfall. At site 2, tilled cells had higher yields than non-tilled cells, with precision tillage showing the maximum relative yield.

Application and Assessment of Precision Deep Tillage

Several fields have been identified in which detrimental soil compaction is suspected. The fields have been divided into 0.4 ha (1 ac) grid cells for the purpose of variable rate application and yield analysis. Multiple cone penetrometer readings have been collected and recorded in each cells to a depth of 700 mm. Precision deep tillage has been applied to depths up to 400mm in which CI is > 1.5 MPa. Crop yield data is compared with CI and NIR imagery to develop a preferred method of applying deep tillage in order to maximize net return.

Evaluation of Gamma Ray Attenuation for Measuring Soil Bulk Density Part I. Laboratory Investigation

Abstract Gamma ray attenuation was evaluated as a means of determining soil bulk density. Experiments were conducted using clay, silt, and sandy loam soils wherein samples were compacted to uniform densities at various moisture contents. We determined the attenuation characteristics of dry soil to be independent of soil texture while being significantly different from that of water. Comparison of gamma density measurements with known soil sample densities indicated that the gamma gauge provided reliable measurement of soil bulk density, provided that the effect of soil moisture on attenuation was accounted for and the manufacturer-prescribed calibration procedure was followed daily. Further, we determined a relationship whereby correction can be made for deviation from the prescribed separation distance between the gamma source and detector.

Automated harvesting of Burley tobacco I. System development.

ABSTRACT A fully automated system for harvesting and handling mature buriey tobacco has been developed. This article identifies the operations essential to this harvesting concept and describes the development of the mechanisms by which they were accomplished. The system detaches, inverts and places mature plants into portable holders for air curing under waterproof covering without requiring any manual handling of the crop. Manual labor currently required to harvest buriey tobacco would be reduced by 80-85% and the system would eliminate the drudgery associated with manual handling. The harvesting system has an approximate capacity of 1.4 to 2.0 ha/day (3.5 to 5.0 ac/day) and is operated by two workers.

COMPACT – A Reclamation Soil Compaction Model Part I. Model Development

A physically based, event oriented soil compaction model, known as COMPACT, was developed as a management or research tool to evaluate the effect of surface mining systems on compaction of soil material during reclamation. Simulation of compaction throughout the soil profile at a surface mining reclamation site requires information describing how equipment moves on the site. The compaction processes that are caused by vehicles throughout the soil profile are described by applying the pressure distribution of the surface contact area of a tire or track to determine stresses in the soil profile. A virgin compression curve is then used to determine bulk density at any point within the soil profile. COMPACT predicts compaction of reconstructed patterns, type of vehicles, and type of soil material. Development of the simulation model is described in this article.

A Mechanical System for Soil Reconstruction

One of the most perplexing problems associated with reclaiming surface–mined lands is excessive compaction of soil due to the heavy earthmoving equipment used during the reclamation process. Over the years, some innovative material handling schemes have been devised to limit vehicle traffic during reclamation on reconstructed soil. However, final grading operations can often create root–limiting bulk densities, which affect plant growth and yield. The purpose of this article is to describe a mechanism designed at the University of Kentucky whereby mine soil can be reconstructed without introducing compaction caused by surface traffic in order for the soil to sustain desirable plant life. The soil handling process for this prototype mechanism is also described. The prototype soil forming mechanism is mounted on the front of a conventional bulldozer. Soil and other rooting media are placed atop graded spoil in long, narrow windrows by scrapers or trucks. As the bulldozer pushes its blade into the windrow, material rises up onto the blade and an auger grinds and displaces soil perpendicular to the direction of dozer travel. The agitated soil is then deposited and leveled in an adjacent berm by the auger. Successive parallel passes of the mechanism results in the construction of a non–compacted rooting layer. Preliminary testing of the prototype yielded a soil construction rate of 330 m3/h (430 yd3/h), which was 12% of the projected theoretical design capacity [2680 m3/h (3500 yd3/h)]. Though the measured capacity is much lower than anticipated, it is believed the actual capacity of the prototype can be increased to 900 m3/h (1177 yd3/h) which would be an acceptable soil forming capacity at most mine sites.

Evaluation of Gamma Ray Attenuation for Measuring Soil Bulk Density Part II. Field Investigation

Abstract A field investigation was conducted at sites near Lexington and Central City, Kentucky, to evaluate the use of gamma ray attenuation for measuring soil bulk density. Experiments were conducted whereby the gamma gauge was calibrated by various means and compared with volumetric cores collected from the field soils. Calibration by the manufacturer’s recommended procedure was determined to be as accurate as more rigorous laboratory calibration or calibration via regression of soil bulk density data, provided that the effect of soil water on gamma attenuation is correctly considered. We also developed a linear regression equation to correct for the occurrence of deviation from prescribed separation distance between the gamma source and detector [254 mm (10 in.)]. Experiments indicated that soil moisture content and soil depth had no effect on the accuracy of determination of dry soil bulk density by the gamma gauge.

Automated Harvesting of Burley Tobacco II. Evaluation of System Performance

ABSTRACT A prototype system for fully automated harvesting of burley tobacco has been developed and tested. Three years of field testing has shown that mechanical losses associated with the system were only slightly higher than via conventional methods. The system performed reliably at a sustained harvesting rate of approximately 1.4 ha/day (3.4 acre/day), while indicating that a rate of 2 ha/day (5 acre/day) should be easily achievable. The system is operated by two workers and reduces conventional labor requirement by approximately 80-85%.

Evaluation of a Mechanical System for Reconstructing Soil on Surface Mined Land

The existence of excessive soil compaction has hindered the surface mining industry from returning land to pre-mining productivity after reclamation, especially on prime farmland soils. Heavy earthmoving equipment used during reclamation tends to generate root-limiting bulk densities that adversely affect plant growth thereby decreasing yields. Therefore, the purpose of this study was to evaluate a mechanism, called the ‘Soil Regenerator,’ which reconstructs soil media at minimum bulk density during surface mine reclamation. The prototype soil forming mechanism was mounted on the front of a conventional bulldozer. Soil was placed in long narrow windrows by a scraper or bulldozer. As the bulldozer pushed into the windrow, soil rose up the blade and was agitated, transported, and deposited by a helicoid auger in a 0.9-m deep berm adjacent to the bulldozer. The capacity of the prototype ranged from 490 to 804 m3/h while producing bulk densities <1.0 Mg/m3 and penetrometer measurements below 0.7 MPa. These measurements demonstrated the capability of the ‘Soil Regenerator’ to eliminate soil compaction on reclaimed surface mined land and to reconstruct soil more suitable for crop growth.

A REDUCED–COST MECHANIZED SYSTEM FOR HANDLING AND CURING MECHANICALLY–HARVESTED BURLEY TOBACCO

An experimental system was tested in which mechanically harvested burley tobacco plants placed onto steel slotted receivers were retrieved from a field, transported to a field curing structure, and placed onto the structure for air curing by a single worker. The system consisted of a tractor–towed, trailer mechanism that engaged and hoisted loads of approximately 360 burley plants of approximately 1 Mg mass. Ten slotted steel rails, 3.05 m long, holding 36 notched plants were placed onto parallel wooden beams suspended at a height of 2.13 m by wooden posts set in the ground. Burley tobacco was cured in this configuration covered by polyethylene. Time–and–motion experiments showed that the system could retrieve tobacco from the field and place it onto a curing structure adjacent to the field at the rate of 0.1 to 0.18 ha/h. Replicated experiments also showed that the system operated with negligible leaf loss due to handling. Finally, experimental results showed that leaf grade index decreased with time that filled tobacco rails were left lying on the ground after being harvested and prior to being retrieved. This study further indicated that the estimated cost of the proposed harvesting system compares favorably with systems that require several manual laborers.