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Acidity distribution within any given soil profile is dependent on mineralogical make-up of the parent material as well as environmental conditions prevalent during the weathering history of the soil. An experiment was designed to study the distribution pattern of exchange acidity, exchangeable aluminum, exchangeable manganese and pH of six acid soils of Western Oregon. 1N KCl extracts of four depths of each soil were obtained and the levels of the parameters mentioned above were measured. It was found that various soil series had different acidity distribution patterns within their profiles. Also, a highly significant linear correlation was observed between exchange acidity and exchangeable aluminum of each soil. Liming acid soils raises pH of the soil extract and improves its fertility status. The rise in pH is due to neutralization of acid groups or acid-producing species present in various forms and on various sites in the soil system. One group of these acid producing species is the exchangeable form of various hydrolyzable cations, especially Al3, H3O+, Mn+2, also perhaps Fe+3, and others. These cations are extracted with solutions of 1N neutral salts such as KC1 and are neutralized by hydroxyls of the applied lime. A second experiment was designed to study the effect of liming, using an incubation procedure, on exchange acidity, exchangeable aluminum, exchangeable manganese and pH of these soils. It was observed that additions of increments of Ca(OH)2 to soil resulted in progressive increase in pH of the soil extract and the relationship between pH and amounts of lime applied was curvilinear with the titration curves approximating linear patterns. As lime rates increase, there was a drop in both Al+3 and exchange acidity content of the soil extract as well as the amount of Mn+2 extracted. For all these three parameters the initial drop was much sharper than the subsequent reductions occurring due to further additions of lime. Point of zero acidity or zero exchangeable aluminum did not necessarily coincide with pH of neutrality. Applications of lime to acid soils improves their crop raising ability, especially with regard to legumes. A third experiment was set up to study the response pattern of alfalfa (Medicago sativa L. var. Du Puits) to lime and phosphorous applications and the effect of such applications on aluminum, manganese, phosphorous, and calcium concentrations of plant tops. Significant yield responses were obtained in some cases but not in others. Phosphorous concentration of the tops was not significantly affected, but aluminum, manganese, and calcium concentrations were affected to varying degrees.
Two soils representative of the coast and three representing the Willamette Valley have been studied for their general chemical characteristics. Exchange capacity and exchangeable cations were determined by the ammonium acetate and the BaCl2-triethanolamine buffer methods. Exchange capacity was also obtained from conductimetric titrations which were run on each soil before and after destroying the organic matter. Potentiometric titrations were run before and after leaching each soil with HCl. Lime requirement was determined by Woodruff's method and also obtained from the pH-lime curves. The two coastal soils, Astoria and Clatsop, have lower pH and base saturation and higher organic matter content and exchange capacity than the Melbourne, Olympic, and Willamette soils from the valley. The Melbourne soil had the highest base saturation percentage and Astoria had the lowest. The amount of exchangeable aluminum was also higher in the coastal soils. The amount of exchange capacity contributed to the organic fraction was 65 per cent in the Olympic and Willamette soils and 50 per cent in the other three. The value for exchange capacity by the different methods was in good agreement in the three valley soils before and after the organic matter was destroyed. In the coastal soils there was no agreement between methods in any case. This would indicate that in the latter two soils, type of clay mineral present may be more of an influence than in the former soils. The potentiometric titration curves showed that the two coastal soils were well buffered and the valley soils were only slightly buffered. After the soils were leached with HCl the Melbourne soil was the only one which indicated a strong acid property. The exchange properties of the soils as affected by additions of lime were studied by incubating the soils for four weeks with added increments of lime. With each added increment of lime the pH increased and exchangeable acidity decreased in each soil. The amount of lime to bring the soils to any given degree of base saturation appeared to be proportional to the magnitude of the exchange capacity and inversely proportional to the degree of base saturation. At any given pH value there was a considerable difference in the degree of base saturation for these soils. This might well be a reflection of the type of minerals present in the different soils. More lime was required to bring the two coastal soils up to pH 6.5 as indicated by the pH-lime relationship curve than that estimated by the Woodruff method. Consistent results were observed in the three valley soils. This suggests that the buffer solution at pH 7 as recommended by Woodruff was not strong enough to neutralize the acidity in the coastal soils. There was good agreement between the two methods in the determination of the exchangeable bases. The BaCl2-buffer method gave much higher values of exchangeable acidity than did the ammonium acetate method. These values, when converted to tons of calcium carbonate, agree fairly closely with the amount of lime required to bring the soils to pH 7 when added directly to the soil. When lime was added above the saturation point the amount of exchangeable calcium as determined by the ammonium acetate method increased but remained relatively constant for the BaCl2-buffer method. The various analysis seem to indicate that the Astoria and Clatsop soils contain predominantly 2:1 type clay minerals while the Olympic and Willamette soils contain predominantly the 1:1 type. The Melbourne soil exhibits properties more closely associated with the coastal soils.
The burgeoning demand on the world food supply, coupled with concern over the use of chemical fertilizers, has led to an accelerated interest in the practice of precision agriculture. This practice involves the careful control and monitoring of plant nutrition to maximize the rate of growth and yield of crops, as well as their nutritional value.
Put Theory into Practice Scarcity of natural resources, higher costs, higher demand, and concerns about environmental pollution- under these circumstances, improving food supply worldwide with adequate quantity and quality is fundamental. Based on the author's more than forty years of experience, The Use of Nutrients in Crop Plants
Co-utilization or blending of residuals offers a unique opportunity to develop products with particular characteristics that are able to target specific customer needs. The very notion of deliberately blending by-products suggests that the recycling and beneficial reuse industries are taking a quantitative step forward towards developing products rather than simply reusing residuals. At the same time that this step provides unique opportunities, it also presents unique challenges. The science associated with the beneficial use of one product may not apply when that product is mixed with another residual. Blending of materials may alter the chemistry of the components of the mixture. This may offer additional benefits, as in the case of disease suppression in composts, or present unexpected problems, as the use of lime-stabilized biosolids has done in Maryland. This book consists of the proceedings of the Beltsville Symposium. The organizers of the Symposium attempted to structure a meeting that would outline both the potential benefits of co-utilization as well as concerns. The editors have divided the proceedings into sections that describe the practical basis for co-utilization of residuals as well as the potential benefits. Specific considerations are described. Finally, case studies include descriptions of successful operations and data that detail results of research involving co-utilization materials. Blending of materials for specific objectives needs to be the focus of any successful co-utilization effort. The scientific implications of the mix need to be determined before a product can be used properly.
Mycorrhizal fungi are microbial engines which improve plant vigor and soil quality. They play a crucial role in plant nutrient uptake, water relations, ecosystem establishment, plant diversity, and the productivity of plants. Scientific research involves multidisciplinary approaches to understand the adaptation of mycorrhizae to the rhizosphere, mechanism of root colonization, effect on plant physiology and growth, biofertilization, plant resistance and biocontrol of plant pathogens. This book discusses and goes into detail on a number of topics: the molecular basis of nutrient exchange between arbuscular mycorrhizal (AM) fungi and host plants; the role of AM fungi in disease protection, alleviation of soil stresses and increasing grain production; interactions of AM fungi and beneficial saprophytic mycoflora in terms of plant growth promotion; the role of AM fungi in the restoration of native ecosystems; indirect contributions of AM fungi and soil aggregation to plant growth and mycorrhizosphere effect of multitrophic interaction; the mechanisms by which mycorrhizas change a disturbed ecosystem into productive land; the importance of reinstallation of mycorrhizal systems in the rhizosphere is emphasized and their impact on landscape regeneration, and in bioremediation of contaminated soils; Ectomycorrhizae (ECM) and their importance in forest ecosystems and associations of ECM in tropical rain forests function to maintain tropical monodominance; in vitro mycorrhization of micro-propagated plants, and visualizing and quantifying endorhizal fungi; the use of mycorrhizae, mainly AM and ECM, for sustainable agriculture and forestry.
In large parts of the developed and developing worlds soil tillage by plough or hoe is the main cause of land degradation leading to stagnating or even declining production levels and increasing production cost. It causes the soil to become more dense and compacted, the organic matter content to be reduced and water runoff and soil erosion to increase. It also leads to droughts becoming more severe and the soil becoming less fertile and less responsive to fertiliser. This book brings together the key notes lectures and other outstanding contributions of the I World Congress on Conservation Agriculture and provides an updated view of the environment and economic advantages of CA and of its implementation in diferent areas of the World.
For Introduction to Soils or Fundamentals of Soil Science courses. Also for courses in Soil Fertility, Forest Soils, Soil Management, Land Resources, Earth Science, and Soil Geography. Developed for Introduction to Soils or Soil Science courses, The Nature and Properties of Soils, 14e can be used in courses such as Soil Fertility, Land Resources, Earth Science and Soil Geography. Now in its 14th edition, this text is designed to help make students study of soils a fascinating and intellectually satisfying experience. Written for both majors and non-majors, this text highlights the many interactions between the soil and other components of forest, range, agricultural, wetland and constructed ecosystems.