performance of paddy grown under saline soils with response to plant nutrition
Saline soils are a major issue for agriculture because salt turns agronomically useful lands into unproductive areas. Salinity affects plant growth and yield in many of crops in varying degreesCrop performance may be adversely affected by salinity-induced nutritional disorders. These disorders may result from the effect of salinity on nutrient availability, competitive uptake, transport or partitioning within the plant. For example, salinity reduces phosphate uptake and accumulation in crops grown in soils primarily by reducing phosphate availability but in solution cultures ion imbalances may primarily result from competitive interactions. Salinity dominated by Na salts not only reduces Ca2 availability but reduces Ca2 transport and mobility to growing regions of the plant, which affects the quality of both vegetative and reproductive organs. Salinity can directly affect nutrient uptake, such as Na reducing K uptake or by Clÿ reducing NOÿ 3 uptake. Salinity can also cause a combination of complex interactions that affect plant metabolism, susceptibility to injury or internal nutrient requirement.
It is well known that the environments of plant rhizospheres are more favourable microhabitats for microorganisms compared to surrounding bulk soils, and these microbes directly or indirectly influence plant growth and development. In addition, as the availability of nutrients for plants is regulated by the rhizospheric microbial activity, any factor affecting this community and its functions influences the availability of nutrients and growth of the plants. Enhanced microbial biomass and activities by rhizosphere effects are important to ecosystem functioning and pollutant degradation in natural ecosystems, plant health as well as in contaminated environments. Exposure of microorganisms to high-osmolality environments triggers rapid fluxes of cell water along the osmotic gradient out of the cell, thus causing a reduction in turgor and dehydration of the cytoplasm. Microbes have developed various adaptations to counteract the outflow of water. The cytoplasm is exposed to high ionic strength to achieve osmotic equilibrium by maintaining a cytoplasmic salt concentration similar to that of the surrounding media.
Soil management for rice cultivation
• Application of gypsum is the handiest method to reclaim sodic soils when the pH is more than 10.
• Shallow rooted rice crop may require 12-15 t ha-1 depending on the soil texture and sodic status.
• Application of organic amendments such as FYM, compost and green manure incorporation, releases abundant Co2, organic acids, lowers pH and releases
• Using resistant varieties, increased seedling hill-1, use of aged seedlings (30-40 days), split application of nitrogen, use of slow release nitrogenous fertilizers (sulphur coated urea, urea super granules), leaching in summer season and raising green manure crops are some of the crop management strategies for better production of rice in sodic soils.
• Saline soils are those soils contains sufficient soluble salts to interfere with crop growth.
• Saline soils remain flocculated and the hydraulic conductivity is more or equal to non saline soils.
• Soil pH is < 8.5, electrical conductivity is > 4.0 dSm-1 at 25oC and Exchangeable sodium percentage is < 15 Cmol(P+) kg-1.
• These soils are with low physiologically available water due to high osmotic potential, poor aeration and toxic effect of sodium carbonate, sodium chloride and sodium sulphate.
• Though rice crop is considered as salt tolerant crop, no rice variety can withstand the adverse effect of high salinity throughout its life cycle. Due to submergence in most of rice soils, imparts tolerance to salinity.
Deep ploughing before submergence, heavy pre-sowing irrigation, high seed rate, closer spacing, green manuring with Dhaincha (Sesbania aculiata), use of organic amendments, placement of N fertilizer below soil surface, split application of N
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under paddy salt soils plant cells under high pressur coming mainly from chloride that disturb organelles membrane and inhibits the cytochrome system then energy for survival becomes problem
Please find enclosed two interesting PDFs for further reference ..
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