Critical Review

The purpose of this section is to provide a critical review of Regional Project S-252, Engineering Principles for Conservation Cropping Systems, which closes in September, 1997. The new regional project on precision farming described in this document is a significant departure from S-252, in objectives, procedures, and participants. In S-252, the majority of the project participants were agricultural engineers; this new project rightfully has participants from several important disciplines, including crop and soil science, engineering, and economics. The following review of S-252 is written by objective, and includes a list of referred journal articles published as a part of the project.
 
Objective 1: Determine the principles which govern the functional performance of machinery systems for conservation cropping.
 
Two locations (NC and AL-ARS) have developed instrumentation and field procedures for tractor mounted penetrometers to develop soil strength maps. NC developed a sensor to measure soil mechanical impedance on-the-go and performed laboratory tests with the sensor. The results indicate that this sensor can determine the depth at which soil mechanical impedance limits root growth to enable tillage decisions on-the-go. A multi-probe cone penetrometer with a GPS receiver was developed at by AL-ARS, and has been used in cooperative research with TN. This research was aimed at determination of the existence, depth, and strength of a fragipan as determined both from the multi-probe cone penetrometer and a ground-penetrating radar (GPS) system. The studies with the GPR system indicate the potential to non-intrusively determine the existence of soil layers which may limit plant growth, particularly in conservation cropping systems. A rapid root measurement system has been developed by VA to enable extensive studies of the effect of conservation cropping systems on root development and growth.
 
KY has adapted a video system and frame grabber to acquire images and identify weeds in crops. Images were collected with six types of ground cover, and a 93.33 classification accuracy was realized to identify each type of ground cover. The ground covers consisted of crab grass, foxtail, lambs quarter, morning glory, velvetleaf, and soil.
 
GA has adapted new GPS technologies to the development of high-accuracy topographic maps using a GPS receiver mounted on a vehicle. The results from these studies have indicated that this equipment can enable the user to rapidly collect sufficient data on large fields in a short time period from which topographic maps with maximum elevation error in the 2-9 cm range can be developed. The topographic map is considered to be an important aspect of conservation cropping systems as it can depict how surface water flows on the field in relationship to the tillage system, and can be related to crop yield.
 
Vehicle traction is an important aspect of the machinery system in conservation cropping systems; AL-ARS has been working on the development of a finite element model of the soil-tire interaction. The model was used to examine rutting behind a wheel, and agreed rather well with data collected in soil bins. KY has developed a three-dimensional finite element model of the soil-tire interaction using a novel system of buried grid marker elements.
 
Objective 2: Integrate fundamental principles necessary to develop design criteria for conservation cropping machinery systems.
 
The influence of the aspect ratio of radial-ply tractor tires on soil compaction and rut depth was investigated in a sandy loam and a clay loam soil, each with loose soil above a hardpan by AL-ARS. For a given tire dynamic load, decreases in the inflation pressure tended to decrease the bulk density and cone penetration resistance in soil beneath the tire tracks, and to decrease tire rut depths.
 
The spatial variation of bulk density and soil cone index was assessed by KY. Cone penetrometer and ground penetrating radar measurements were made to indicate yield-limiting soil compaction. The results indicated the potential to provide 50% fuel savings my using site-specific deep tillage procedures, rather than deep tillage for the entire field. The work at KY also included extensive grid soil sampling for selected fertilizer levels. This data was used to assess the economics of site-specific versus field-average nutrient management approaches.
 
Objective 3: Integrate machinery and agronomic/horticultural principles to improve conservation cropping production systems from the standpoint of environmental quality, productivity, profitability, crop quality, and long-term sustainability.
 
SC and FL worked on the utilization of waste material as soil amendments. SC developed equipment to broadcast and for band application of municipal solid waste compost at selected rates for cotton production. They found a yield increase which was directly proportional to the application rate. In Florida, the influence of yard waste compost on plant-parasitic nematode densities and corn forage yield were determined over three seasons at two sited. Selected types of nematodes were reduced by compost treatments, but the effect usually did not occur until the third season. Corn forage yield was increased by compost treatment, with increases ranging from 10 to 212%.
 
Narrow-row and wide-row cotton production systems were compared in terms of yield and crop response for conventional and conservation cropping methods under coastal plain soil conditions in SC. No significant difference in yield due to row spacing in 1996 was observed and there was no significant difference in yield between cotton interseeded into standing wheat two weeks before harvest. There was a significant difference in the height of the low boll between the mono-crop and interseeded cotton. Yield losses due to the inability of the cotton picker to pick low bolls was greater for the mono-cropped treatments.
 
Conventional, no-till and one-pass wheat was planted in SC soybean stubble residue using a one-pass planting system. Wheat yields from the one-pass system were 7% higher than those for conventional and 64% higher than those for a no-till system. Soybeans following one pass wheat yielded 13% higher than a chisel plow treatment and 29% higher than no-till plots. The narrow row soybeans yield was 437 kg/ha higher than the wide row.
 
Experiments in Virginia were conducted for a fifth year using a mechanically-killed rye cover crop with a commercially available conservation till planting system instead of a prototype used preciously. Crop stands and yields in the sustainable plots were not as good as the previous three years, although there was no significant difference between the conventional and sustainable yields. Analyses showed an energy savings of 27% per dollar of return for the sustainable system. Virginia also conducted an energy and cost benefit analysis for a precision farming system used on 13 fields on 11 farms. Seven of the 13 fields showed a net dollar benefit from the precision farming system.
 
Summary:
 
The use of winter cover crops and machinery systems to reduce soil erosion and nitrogen crop requirements continues to be important for sustainability of agriculture. The yield of corn planted into the cover crops has been shown to be as good or better than corn yield with conventional tillage yields. One-pass interseeding research has indicated that field operations can be more efficient to increase profit margins, and with less environmental impact.
 
Soil and plant sensor development in this project has improved our ability to provide data for tillage and planting decisions to optimize field operations. These sensors are being developed to locate hardpans, compacted trafficked areas, weeds, soil moisture, and plant residue.
 
It has been shown that adopting a sustainable conservation tillage system may not be as simple as eliminating tillage. Several studies have indicated the necessity of deep tillage to alleviate soil compaction. It has also been shown that the use of cover crops will enhance moisture retention and reduce purchased-nitrogen inputs. The work has also indicated that the use of precision farming technologies may also minimize crop inputs, and allow the farmer to manage small land units to minimize inputs and provide environmental benefits.
 
In recent years, it has been realized that all agricultural technologies can perhaps be included under the umbrella of an overall agricultural system which has been given the name "Precision Farming". Conservation cropping systems are considered to be a part of precision farming, which may or may not be utilized for specific farming operations, depending upon many factors. The development of soil and plant sensors in S-252, as well as various types of conservation cropping systems, has naturally brought the S-252 research team into the precision farming arena, where much work remains to develop appropriate management techniques which can enable the farmer to properly manage every part of each field to optimize profit and to minimize the environmental impact of farming practices.
 
Refereed Journal Articles- 1993
 
Clark, R. L. and G. VandeLinde. 1993. A rapid automatic tractor ballast system. TRANS. of the ASAE 36(5):1261-1266.
 
Clark, R. L., D. E. Radcliffe, G. W. Langdale, and R. R. Bruce. 1993. Soil strength and water infiltration as affected by paratillage frequency. TRANS. Of the ASAE 36(5):1301-1305.
 
Gallaher, R. N. And R. McSorley. 1993. Population densities of Meloidogyne Incognita and other nematodes following seven cultivars of cowpea. Nematropica 23(1):21-26.
 
Lilly, D. P., D. L. Wright, I. D. Teare, R. N. Gallaher, and R. L. Stanley. 1993. Tropical corn as affected by planting date, nitrogen, and water. Soil and Crop Sci. Soc. Of Florida 52:21-27.
 
McSorley, R., and R. N. Gallaher. 1993. Population dynamics of plant-parasitic nematodes on cover crops of corn and sorghum. J. Of Nematology 25(3):446-453.
 
Morrison, J. E., Jr., C. H. Huang, D. L. Lightle, and C.S.T. Daughtry. 1993. Residue measurement techniques. JSWC 48(6) 479-483.
 
Schafer, R. L., C. E. Johnson, A. J. Koolen, S. C. Gupta, and R. Horn. 1992. Future research needs in soil compaction. TRANS. Of the ASAE 35(6):1761-1770.
 
Refereed Journal Articles- 1994
 
Burt, E. C., D. W. Reeves and R. L. Raper. 1994. Energy utilization as affected by traffic in conservation and conventional tillage systems. TRANS. Of the ASAE 37(3):759-762.
 
McSorley, R. And R. N. Gallaher. 1994. Effect of liming on soil nematode populations under soybean. Soil and Crop Sci. Soc. Fla. Proc. 53:22-25.
 
McSorley, R. And R. N. Gallaher. 1994. Effect of tillage and cover crop management on nematode densities on corn. Supplement of Journal of nematology 26:669-674.
 
Morrison, J. E., Jr. and F. W. Chichester. 1994. Tillage system effects on soil and plant nutrient distributions on vertisols. J. Prod. Agric. 7(3):364-373.
 
Morrison, J. E., Jr., and K. N. Potter. 1994. Fertilizer solution placement with a coulter-nozzle applicator. Appl. Engr. Agric. 10(1):7-11.
 
Mullins, G. L., D. W. Reeves, C. H. Burmester and J. H. Bryant. 1994. Effects of in-row subsoiling and deep placement of K on root growth and K uptake of cotton. Agron. J. 86:136-139.
 
Raper, R. L., C. E. Johnson and A. C. Bailey. 1994. Coupling normal and shearing stresses to use in finite-element analysis of soil compaction. TRANS. Of the ASAE 37(5):1417-1422.
 
Raper, R. L., D. W. Reeves, E. C. Burt, and H. A Torbert. 1994. Conservation tillage and reduced traffic effects on soil condition. TRANS. Of the ASAE 37(3):763-768.
 
Torbert, H. A. And D. W. Reeves. 1994. Fertilizer N requirements for cotton production as affected by tillage and traffic. Soil Sci. Soc. Am. J. 58:1416-1423.
 
Refereed Journal Articles 1995
 
Bailey, A. C., R. L. Raper and C. E. Johnson. 1995. An integrated approach to soil compaction prediction. Journal of Ag. Eng. Res. 61:73-80.
 
Clark, R. L. And D. Zhang. 1995. Ballast and traction modeling of a wide span tractor. TRANS. Of the ASAE 38(6):1613-1620.
 
Liang, P., C. G. Bowers, Jr., and H. D. Bowen. 1995. Finite element model to determine the shape factor for soil air permeability measurements. TRANS. Of the ASAE 38(4):997.
 
McSorley, R. And R. N. Gallaher. 1995. Cultural practices improve crop tolerance to nematodes. Nematropica 25:53-60.
 
McSorley, R. and R. N. Gallaher. 1995. Effect of yard waste compost on nematode densities in vegetable crops. Supplement to Journal of Nematology 27:554-549.
 
Morrison, J. E., Jr., J. Lemunyon, and H.C. Bogusch. 1995. Sources of variation and performance of nine devices when measuring percent residue cover. TRANS. Of the ASAE 38(2)521-529.
 
Porter, P. M. And A. Khalilian. 1995. Wheat response to row spacing in relay intercropping systems. Agronomic Journal 87(5):999-1003.
 
Potter, K. N., H. A. Torbert, and J. E. Morrison, Jr. 1995. Tillage and residue effects on infiltration and sediment losses on vertisols. TRANS. Of the ASAE 38(5):1413-1419.
 
Raper, R. L., A. C. Bailey, E. C. Burt, T. R. Way, and P. Liberati. 1995. Inflation pressure and dynamic load effects on soil deformation and soil-tire interface stresses. TRANS. Of the ASAE 38(3): 685-689.
 
Raper, R. L., A. C. Bailey, E. C. Burt, T. R. Way, and P. Liberati. 1995. The effects of reduced inflation pressure on soil-tire interface stresses and soil strength. Journal of Terramechanics 32(1):43-52.
 
Reeves, D. W. And G. L. Mullins. 1995. Subsoiling and potassium placement effects on water relations and yield of cotton. Agronomy Journal 87:847-852.
 
Reeves, D. W., D. D. Tyler, and W. L. Hargrove. 1995. Winter cover crops. IN: Crop Residue Management to Reduce Erosion and Improve Soil Quality. USDA-ARS Conservation Research Report No. 39:27-29.
 
Torbert, H. A. And D. W. Reeves. 1995. Traffic and residue management systems: effects of fate of fertilizer N in corn. Soil & Tillage Research 33:197-214.
 
Torbert, H. A. And D. W. Reeves. 1995. Interactions of traffic and tillage applied to cotton on N movement below the root zone of a subsequent wheat crop. Soil & Tillage Research 33:3-16.
 
Refereed Journal Articles 1996
 
Bailey, A. C., R. L. Raper, T. R. Way, E. C. Burt and C. E. Johnson. 1996. Soil stresses under a tractor tire at various loads and inflation pressures. J. Terramechanics 33(11):1-11.
 
Entry, J. A., D. W. Reeves, C. B. Backman and R. L. Raper. 1996. Influence of wheel traffic and tillage on microbial biomass, residue decomposition and extractable nutrients in a Coastal Plain Soil. Plant & soil 180:129-137.
 
Entry, J. A., D. W. Reeves, E. Mudd, W. J. Lee, E. Guertal and R. L. Raper. 1996. Influence of compaction from wheel traffic and tillage on arbuscular mycorrhizae infection and nutrient uptake by Zea mays. Plant & Soil 180:139-146.
 
McSorley, R. And R. N. Gallaher. 1996. Effect of yard waste compost on nematode densities and corn yield. Supplement to Journal of Nematology 28:655-660.

Pearman, B. K., T. R. Way, C. E. Johnson, E. C. Burt, A. C. Bailey and R. L. Raper. 1996. Soil stresses and rut depths from tires of a mechanical front wheel drive tractor. TRANS. Of the ASAE 39(4):1249-1257.

Ping, L., C. G. Bower, Jr. and H. D. Bowen. 1996. Effects of insert edge design and insertion and sealing techniques on soil air permeability measurements. TRANS. Of the ASAE 39(4):1269-1273.