Search

The 'degree of compactness' is a useful parameter to study soil compaction and represents the current bulk density in relation to the bulk density of the same soil in a reference state. The objectives of this study were to: (i) determine the best compression stress to establish the reference bulk density in the uniaxial compression test using undisturbed samples; (a) quantify the effect of texture on degree of compactness, and (Hi) evaluate the influence of degree of compactness on selected soil physical properties and crop yield. Six soils under no-tillage from southern Brazil were used and the reference bulk density was evaluated on soil samples equilibrated to the matric suction of 33 kPa and subjected to uniaxial compression test. Soil macroporosity, mechanical penetration resistance, root growth, and yield of soybean were also evaluated. For undisturbed soil samples, stresses ≥ 800kPa (particularly the stress of 1600kPa) arc appropriate to determine the reference bulk density. Degree of compactness is independent of clay content and is associated with changes in soil physical properties. A degree of compactness ~100% restricted root growth of soybean, whereas the highest soybean yield was obtained with a DC of 82% for Alfisols and Ultisol, and 85% for Oxisols. Additional keywords: reference bulk density, relative compaction, soil compaction, uniaxial compression., Introduction Soil compaction is defined as the process of decreasing total porosity (especially air-filled porosity), with a consequent increase in bulk density and soil penetration resistance and decrease in water [...]

Abstract: Soybean cyst nematode (SCN) (Heterodera glycines Ichinohe; HG) is one of the most destructive pests of soybean (Glycine max (L.) Merr.) in the United States. Over 100 SCN-resistant accessions [...]

A study evidence for the involvement of a new genetic locus that controls soybean cultivar specificity is demonstrated based on the finding from the symbiosis between Sinorhizobium fredii USDA257 and soybean [Glycine max (L.) Merr. Compared to the formerly characterized soybean cultivar specificity locus nolBTUVW, inactivation of the gcv locus had no discernible effect on the secretion of nodulation outer proteins of USDA257.

A study was conducted to determine the effects of red clover, soybean, and barley plant residues and of glucose on denitrifier abundance, denitrification gene mRNA levels, nitrous oxide ([N.sub.2]O) emissions, and denitrification rate quantified in anoxic soil microcosms for 72 h. Denitrification and respiration was found to increase in soil amended with organic carbon, including plant residues, compared to unamended soil.

A multilocus sequence-based analysis of 80 soybean nodule isolates obtained from India, Myanmar, Nepal, and Vietnam is presented. The results based on mapping climate types and geographic origins of the isolates on the species tree showed all species to display epidemic clones and have broad geographic and environmental distribution ranges.

Nutrients attributed to the consumption of soybean-derived foods are found in everyday foods and the requirement of the consumption of high quantities of soy-based foods discussed. The myth surrounding consumption of soy based foods for better nutrition and protection against disease is exposed.

The involvement of nodulation gene regulation and quorum sensing in the restriction of nodulation by Bradyrhizobium japonicum is discussed. Results suggest the usefulness of nodD2 mutant of B. japonicum for enhancing soybean nodulation at high inoculum densities.

The rise in soybean production in Brazil has generated concern among environmental community as they feel that natural tropical environments of the Amazon Basin are being converted to soybean fields. A case study in Vilhena, Rondonia, Brazil, in the southwestern Amazon Basin reveals that the production increase is attributed to slight expansion of already existing fields, and conversion of already deforested land.

WESTERN BLOT ANALYSIS OF DROUGHT TOLERANCE IN SOYBEANS. Shana Benton [*], D. Long, C. Caudle, and E. Lewis Myles, Tennessee State University, Nashville, Tennessee. Stress in any organism can be [...]

Large swathes of the Brazilian Amazon have come to resemble the midwestern United States in recent years, having been planted with soya as far as the eye can see. This [...]