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Fluid Journal : Fluid Journal 1999-2001
1 Fluid Journal Spring 2001 Summary: With the advent of prescription application of nutrients and the potential to use biotechnology to engineer efficient root systems, research efforts directed toward the "hidden half" of the crop are now more important than ever. The first step in improving effectiveness of nutrient management practices is understanding how plant root systems interact with the soil. Basic knowledge will ensure that maximum soil productivity and profitability are sustained, and that the environmental impact of nutrient use is minimized. Due to the complexity of the plant-soil system, much of the research addressing fertilizer responses by crop plants has taken somewhat of a "black box" approach--- where crop responses to several increments of a soil amendment are measured. This approach is not without merit in that fertilizer recommendations have been developed for a range of crops grown under varying climatic conditions on many types of soil. However, if data are closely examined, significant scatter is readily apparent. The scatter can be attributed to variation in the growth and distribution of plant root systems. Nutrient uptake by plants growing in soil involves both soil and plant processes. Soil tests provide a measure of soil nutrient supply. If calibrated for individual crop species, soil tests can to some degree account for differences in the ability of plants to absorb nutrients. Nevertheless, we cannot expect a perfect fit because changes in root growth and function cause changes in crop response to fertilizer, even when Dr. J. L. Kovar The Role Of Roots In Maximum Soil Productivity A significant amount of production capital and labor are expended in an effort to provide an environment conducive to plant root growth. Don't ig- nore your investment, researcher advises. the soil supply of nutrients remains at a constant level. With the advent of prescription application of nutrients and the potential to use biotechnology to engineer efficient root systems, research efforts directed toward the "hidden half" of the crop are now more important than ever. The purpose of this discussion is to 1) provide a brief overview of environmental factors affecting root growth and development, and 2) discuss the relationship of root growth to nutrient availability and uptake. What affects root growth Since most of the elements essential for plants are absorbed by roots, an understanding of root system characteristics is important in determining the most effective method of nutrient management. Root systems of crops species are classified as being fibrous or taprooted, with each type occurring in annual and perennial species. The ability of the root system to extract nutrients and water from the soil depends on its morphological and physiological characteristics. Soil physical and chemical properties can affect root growth rate, root morphology, and ultimately, nutrient uptake. Mechanical impedance, soil water content, and soil temperature often interact to affect root growth. When soils are compacted, bulk density increases and the number of larger pores decreases, leading to increased resistance (soil strength) to root growth. Roots growing into compacted soil must displace soil particles, so that the rate of root elongation decreases as soil strength increases. In soil without significant compaction, roots will grow
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