Abstract
AbstractDr. Nil Ratan Dhar Memorial Lecture Soil could be perceived as a four dimensional system where a broad three dimensional structural fabric is filled by dynamic and reactive colloidal constituents. There are interconnected relationships between authegenic, neogenic and stable-phase crystallite constituents, most of which are in nano-phase, and the system seldom reaches equilibrium. Also, variations in composition, pH, and other properties make soil unique at each place. Therefore, understanding of soil system helps to develop insight into mobility and reactivity of nano-materials. The origin of nanoscience can be traced to the discovery that clay minerals were crystalline and of micrometer size. The unit cell dimensions of clay minerals are in nanometer scale in all three axes (x, y, and z). Nanoclays played a catalytic role in the synthesis of ribosome in RNA, a process that led to genesis of life on Earth. This fact makes clays the most life-compatible material in nanotechnology. Methods followed in industry (like melting materials at a high temperature) cannot be copied for agricultural nanotechnology. Yet this is no hindrance, because nanoclays obey the laws of ion exchange, adsorption-desorption, aggregation-dispersion and solubility-precipitation, to name a few. The most vital yardstick is that the nanosystem has to be capable of releasing nutrient ions in plant-available forms. Clays have both covalent and ionic bonds; a feature unique for developing passive control systems for nutrient supply mechanisms. There are numerous examples in soils, where bonds are changed from one type to another through isomorphous substitution or insertion of small ions, or by the use of organic compounds. Nanotechnology in clay system does not promise a control system such as we experience in electrical machines, or in satellites, or in chemical reactors. But, it has to be a knowledge based passive system, and for sure, it is going to create millions of rhizospheres in an acre of land to support the growth of millions of plants of a crop; a breakthrough to take agriculture into the new millennium.
Highlights
He propounded importance of OM in soil fertility at a time when fertilizers were considered wonder material, and OM had been virtually discarded
The unit cell dimensions of clay minerals are in nanometer scale in all three axes (x, y, and z) ordered arrangements, large adsorption capacity, shielding against sunlight (UV radiation), ability to concentrate organic chemicals, and ability to serve as polymerization templates
Si replaced by Al - increase of 12.2% ionic character in silicon tetrahedron If Si is replaced by Al in zeolite framework structure, the tunnel diameter changes Organic materials can bridge different bonds
Summary
A TRIBUTE “The roots below the earth claim no rewards for making the branches fruitful”. He propounded importance of OM in soil fertility at a time when fertilizers were considered wonder material, and OM had been virtually discarded. Global Warming was unheard of at that time. He advocated biological management of N, when world could not perceive GHG emission, nor assess its magnitude from farm fields
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