Soil nutrition

Clearly, the concentration of exudates and rhizodeposits depends on soil nutritional status and on plant species this may affect the microbial utilization and subsequent turnover of rhizodeposits in soil. 

By predicting PbB levels, a determination can be made about what health impacts may be occurring at a given site. This will assist health assessment personnel in deciding whether further action is needed. A site-specific evaluation must be made before reaching any conclusions (e.g., pica children, ground cover over contaminated soil, nutritional status and age of the population, etc.). Issues relevant to children are explicitly discussed in Sections 2.6, Children s Susceptibility, and 5.6, Exposures of Children. 

Baumann, T. W. Gabriel, H. Plant Cell Phvsiol. 1984, 25, 1431-36. Suzuki, T. Waller, G. R. Proc. Int. Conf. Soils Nutrition Perennial Crops 1986, 259-66. 

The provision of photosynthetic organisms with elements of soil nutrition is related to the inner part of soil s biogeochemical structure and is connected to two major soil components. The first of these is the dead organic matter and the second is the soil s... 

While a number of variables are outside of the control of the plant grower, some are within his control. The grower should consider the influence of plant genetics, soil nutrition, and water regime in determining the flavor of his crop. It seems that appearance and yield per acre are the two major criteria of success in growing produce. Flavor should become a more significant consideration. 

Rehfuess, K.E. (1989). Acidic deposition - extent and impact on forest soils, nutrition, growth and disease phenomena in central Europe a review, fater. Air, and Soil Pollution 48, 1-20. 1987 5... 

Soils should contain 0.13 to 0.30 ppm of cobalt for proper animal nutrition. 

Calcium. Soil minerals are a main source of calcium for plants, thus nutrient deficiency of this element in plants is rare. Calcium, in the form of pulverized limestone [1317-65-3] or dolomite [17069-72-6] frequendy is appHed to acidic soils to counteract the acidity and thus improve crop growth. Such liming incidentally ensures an adequate supply of available calcium for plant nutrition. Although pH correction is important for agriculture, and liming agents often are sold by fertilizer distributors, this function is not one of fertilizer manufacture. 

In 1956 selenium was identified (123) as an essential micronutrient iu nutrition. In conjunction with vitamin E, selenium is effective iu the prevention of muscular dystrophy iu animals. Sodium selenite is adrninistered to prevent exudative diathesis iu chicks, a condition iu which fluid leaks out of the tissues white muscle disease iu sheep and infertility iu ewes (see Eeed ADDITIVES). Selenium lessens the iacidence of pneumonia iu lambs and of premature, weak, and stillborn calves controls hepatosis dietetica iu pigs and decreases muscular inflammation iu horses. White muscle disease, widespread iu sheep and cattle of the selenium-deficient areas of New Zealand and the United States, is insignificant iu high selenium soil areas. The supplementation of animal feeds with selenium was approved by the U.S. EDA iu 1974 (see Eeed additives). Much of selenium s metaboHc activity results from its involvement iu the selenoproteia enzyme, glutathione peroxidase. 

In paints, zinc oxide serves as a mildewstat and acid buffer as well as a pigment. The oxide also is a starting material for many zinc chemicals. The oxide supphes zinc in animal feeds and is a fertilizer supplement used in zinc-deficient soils. Its chemical action in cosmetics (qv) and dmgs is varied and complex but, based upon its fungicidal activity, it promotes wound healing. It is also essential in nutrition. Zinc oxide is used to prepare dental cements in combination with eugenol and phosphoric and poly(acrylic acid)s (48) (see Dental materials). 

New cocoa hybrids and selections have been developed in Malaysia and other countries that produce significantly higher yields in select soil and climate conditions. In addition, high density plantings have demonstrated higher and earlier yield in Malaysia and the Philippines. Low or no shade cocoa has also proven to increase yields. However, both high density and reduced shade cocoa production requires additional inputs of management and nutrition. Additional inputs to control pests and diseases also maybe required. 

The magnitude and composition of root exudates are a reflection of the physiological condition of the plant imposed by factors related to light (intensity, duration, and quality), temperature, soil pH, anaerobiosis, soil moisture, soil type, and nutritional status. The in-... 

The nutrition needs of the future will be met with more limitations than in the past on the use of energy and restrictions on contamination of the environment. The maintenance of natural resources will receive much more attention than in the past. Concerns will increase regarding desertification, deforestation, urbanization, salinification, soil and water degradation, and atmospheric pollution. There is considerable difficulty in delineating these limitations, particularly as one considers the responsibilities and interests of developed and developing countries. The role of economics offers an additional challenge in working out these relationships. 

The reservoir representing the land (2) is defined as the amount of P contained in the upper 60 cm of the soil. This rather narrow definition of the land reservoir is made because it is through the upper portions of the soil system that the major interactions with the other P reservoirs occur. Specifically, most plants receive their nutritive P needs from the upper soil horizons and the return of P to the soil system by the decomposition of plant matter is also concentrated in this upper soil zone. Similarly, the major interactions with the atmosphere, ground waters, and rivers occur near the... 

Photosynthesis and gas exchange of leaves are affected by many stresses including drought, flooding, salinity, chilling, high temperature, soil compaction and inadequate nutrition. Many, but not all, of these stresses have symptoms in common. For example, stomatal conductance and the rate of assimilation of CO2 per unit leaf area often decrease when stress occurs. Further, it is possible that several of the stresses may exert their effects, in part, by increasing the levels of the hormone abscisic acid (ABA) in the leaf epidermis. This hormone is known to close stomata when applied to leaves. 

As mentioned before and in Chaps. 4 and 6, the concentration of rhizode-position decreases as the distance from the rhizoplane increases, whereas the opposite generally occurs for the concentration of any plant nutrient in soil. In this context, the role of rhizospheric soil, rather than that of the bulk soil, is crucial for plant nutrition. It has also to be considered that very different situations can occur depending on the type of nutrient (24) and the nutritional status of plants (see Chap. 3) furthermore, different portions of the root system are characterized by differential nutrient-specific rates of uptake (25). All the above statements point to the necessity of reconsidering the concept of plant nutrient availability giving more importance to the situation occurring in the soil surrounding the root. 

L. BeiBner and W. Romer, Improving the availability of phytate-phosphorus to sugar beet (Beta vulgaris L.) by phytase application to soil, 9th International Kollo-c/uiuin for the Optimization of Plant Nutrition, Prague, Czech Republic, 1996. p. 327. 

S. Tagaki, The iron acquisition system in graminaceous plants and mugineic acids, Niitriophysiology of Metal Related Compounds (Japanese Society of Soil Science and Plant Nutrition, eds.), Hakuyushia, Tokyo, Japan, 1990, p. 6. 

K. Kanazawa, T. Ohata, G. Miha,shi, S. Fushiya, N. Nishizawa, M. Chino, and S. Mori, Inductions of two enzyme activities involved in biosynthesis of mugineic acid in Fe deficient barley roots. Iron Nutrition in Soils and Plants (J. Abadia ed.), Kluwer Academic Publishers, Dordrecht, The Netherlands, 1995, p. 37. 

A. D. Rovira, Root excretions in relation to the rhizosphcre effect IV. Influence of plant species, age of plant, light, temperature and calcium nutrition on exudation. Plant Soil 11 55 (1959). 

Z. G. Cardon, Influence of rhizodeposition under elevated CO, on plant nutrition and soil organic matter. Plant Soil 187 211 (1996). 

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