Soil Fertility PDF

1. Most soils are not naturally “fertile” 2. Employee green manure programs as a means of maintaining soil organic levels as well as providing a means for recirculating essential plant nutrient elements 3. Planting of a cover crop between growing seasons will minimize soil erosion and...

1. Most soils are not naturally “fertile” 2. Employee green manure programs as a means of maintaining soil organic levels as well as providing a means for recirculating essential plant nutrient elements 3. Planting of a cover crop between growing seasons will minimize soil erosion and the potential loss of essential plant nutrient elements by profiled leaching 4. Turning under a cover crop will provide a source of absorbed essential plant nutrient elements when decomposition occurs Characteristics of an Ideal Soil 1. A loamy in texture for ease of air and water movement into the soil 2. An organic matter content sufficient to sustain microganisms population 3. Good textural and organic matter characteristics that contribute to soil tilth 4. Sufficient clay colloids to hold reserved essential plant nutrient elements in soil moisture 5. A soil structure that promotes proliferation of plant roots into the soil mass and ease of water drainage and air exchange at the soil surface 6. A deep soil profile with a permeable subsoil allowing for root penetration and normal soil water drainage 7. A subsoil fertility that promotes root growth Significant effect of soil fertility in crop production 1. There is leaching and wash of the topsoil once the vegetative cover is removed 2. At the beginning of cultivation, all the nutrients are at their peaks, but as cultivation continues the nutrient elements tend to leach out 3. The use of heavy equipment's accelerated soil erosion, destroys soil structure and accelerates decline of soil organic matter 4. Soil organic matter functions as the principal source of nutrients and its decline affects both the yield and soil nutrients 5. In the tropics, organic matter decomposes four times a faster than under the temperate conditions 6. Under continuous land use, addition of fertilizers results in a great decline in total nitrogen and soil pH 7. The use of inorganic fertilizer alone has not been effective as a farming practice, which employs both organic and inorganic manures with fallow Importance of Soil Fertility 1. The impacts of soil fertility are reflected in most of the SGDs, as they contain economic, social, and environmental aspects 2. A fertile soil also provides essential nutrients for plant growth, to produce healthy food with all the necessary nutrients needed for human health  3. Good management of soil fertility can help reduce soil, water and air pollution, regulate water resources availability, support a diverse and active biotic community, increase vegetation cover and allows for carbon neutral footprint Nearly 90 elements are taken up by plants but all are not essential Macronutrients or major nutrients are found and required in plants in relatively higher amounts than micronutrients. Micronutrients are required by plants in relatively small quantities but are as essential as the macronutrients The movement of nutrients in soil varies greatly and largely influences their availability to the plants The appearance of deficiency symptoms in plants chiefly depends upon the extent and the rate of re-translocation of nutrients from older to younger issues within plants Sufficient is independent of the environment since increased root growth will expand into areas where contact exchange uptake is the same pH is the common logarithm of the reciprocal of the hydrogen ion concentration of a solution Each nutrient is taken up in an "ionic" or charged form Nutrient uptake by roots is dependent on: 1. Root growth and soil exploration 2. The ability to absorb nutrients 3. The nutrient concentration at the root surface Plants feed mainly by taking nutrients from the soil through their roots. Leaf stomata can also absorb the nutrients The pineapple plants are noted for absorbing fertilizer nutrients from the leaf bases Important Aspects Of The Influence Of Nutrient Supply On Plant Growth 1. Plants need certain concentrations of nutrient in their tissue for active growth 2. Nutrient requirement comes somewhat in advance of plant growth 3. Insufficient nutrient uptake results in slight to severe deficiencies 4. Slight deficiencies are not visible and denotes "hidden hunger" 5. Deficiency symptoms indicate a severe shortage of the nutrient in question 6. High yields are only obtained where all nutrients are in the optimal supply range 7. The nutrient with the lowest supply determines the yield level  8. Many mistakes in fertilization can be attributed to disregarding the law of the minimum 9. It is easier to correct nutrient deficiencies than to eliminate nutrient toxicities In order to produce high yields, plant nutrition requires a continuous effort to eliminate minimum factors and provide balanced nutrition in the optimal range An optimal nutrient supply requires: 1. Sufficient available nutrients in the rootzone of the soil 2. Rapid transport of nutrients in the soil solution towards the root surface 3. Satisfactory root growth to access available nutrients 4. Unimpeded nutrient uptake, especially with sufficient oxygen present 5. Satisfactory mobility and activity of nutrients within the plant 6. Law of Minimum and Law Diminishing Returns Ammonium is abundant in a reduced layer of paddy soils Nitrate is more abundant in aerobic soils and most absorbed by plants NO3- is often the predominant form of N NH4+ is easily oxidized by bacteria in aerobic soil to NO3- as soon as NH4+ appears NO3- uptake occurs against as electrochemical gradient or energy requiring NH4+ uptake is optimum at neutral pH and decreases as pH decreases NO3- uptake increases with decreasing pH and decreases with increasing pH probably due to competition with OH NO3 is toxic to plants The fertilizer urea which is converted to NH4+ by urease in soil can be taken directly by plants, though at slower rate than NO3- The fixed potassium cannot be replaced by ordinary exchange methods and consequently is referred to as non-exchangeable potassium