Advances in Soil Science

1. Front Matter

   Pages i-ix

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2. Physical Fractionation of Soil and Organic Matter in Primary Particle Size and Density Separates

   • Bent T. Christensen

   Pages 1-90

3. Soil Water Repellency

   • M. G. Wallis, D. J. Horne

   Pages 91-146

4. Stem-Nodulating Legume-Rhizobium Symbiosis and Its Agronomic Use in Lowland Rice

   • J. K. Ladha, R. P. Pareek, M. Becker

   Pages 147-192

5. Analysis of Lognormal Data

   • T. B. Parkin, J. A. Robinson

   Pages 193-235

6. Nutrient Transformations in Soils Amended with Green Manures

   • Yandvinder-Singh, Bijay-Singh, C. S. Khind

   Pages 237-309

7. Back Matter

   Pages 311-314

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The key to sustaining the soil resource base is to maintain, or enhance, soil quality. Soil quality cannot be seen or measured directly from the soil alone but is inferred from soil characteristics and soil behavior under defined conditions. In essence, the quality of soils is analogous to the health of humans, and just as there is no single characteristic that can be measured to quantify a person's health, there is no single measurement that can quantify soil quality. However, there are certain characteristics, particularly when considered together, that are good indicators. Soil quality, just as human health, can be maintained or enhanced by good management practices; and seriously degraded-sometimes irrevers­ ibly-with poor practices. Soil quality is also important because it has direct and indirect effects on air quality and water quality. While the enhancement of soil quality does not always assure parallel improvements in the quality of air and, particularly, water resources, this is often the case. However, soil deg­ radation is invariably accompanied by degraded qualities of both air and water resources. The consensus among many scientists is that the greatest challenge is not increasing production, but preventing serious deterioration of the soil and water resource base so that the production level can be sustained.

• Phosphor
• rice
• soil
• soil science
• water

• USDA Conservation & Production Research Laboratory, Bushland, USA

  B. A. Stewart

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