Fertilizers application rates

A recent review of research on phosphorus input to surface waters from agriculture highlights the variability of particulate and dissolved phosphorus contributions to catchments. The input varies with rainfall, fertilizer application rates, the history of the application of the fertilizer, land use, soil type, and between surface and sub-surface water. The balance struck between export of nutrients from the catchment and recipient-water productivity is the primary factor which controls its quality. 

Fertilizer application rates of, 77 124-126 techniques for, 77 124 Fertilizer coating, ionomers as, 74 483 Fertilizer industry growth of, 23 789... 

Improve fertilizer application rates (reducing Nitrogen while increasing Phosphate and Potassium) ... 

Various mathematical models or algebraic equations can be used to estimate fertilizer response curves such as those shown in Figures 2.10 and 2.11, Mathematical models selected for this purpose are equations that properly represent agricultural production-fertilizer relationships that can be estimated using statistical methods. A quadratic function model is commonly used to estimate fertilizer response functions that properly represent agricultural output increasing at a decreasing rate as a result of increased fertilizer application rates. A quadratic response function model may be written as ... 

Consequently, the most revealing way to compare the intensity of fertilization is to use averages for individual crops, but few countries regularly publish such data. The best available global breakdown of nitrogen fertilizer use by individual crops comes from worldwide surveys organized by the IF A, FAO, and IFDC. Fertilizer application rates based on informed estimates, rather than on actual field surveys, are now available for more than ninety countries. ... 

Source Harris, G. 1998. An Analysis of Global Fertilizer Application Rates for Major Crops. Paris IFA (http //www.fertilizer.org). 

The sorption and degradation characteristics listed for most pesticide compounds in terms of partition coefficients and half-lives relate only to a (standard) fertile, organic clayey soil and must not to be taken as representative of the permeable sandy soils widely developed on aquifer outcrops. Thus leaching of 1% of original application rates, and perhaps significantly higher, could easily occur for certain compounds on permeable soils. 

In the same regard, PPCP introductions through manure and biosolids that are applied to arable land is enhanced by the typically high application rates of these forms of crop fertilizers rates that are usually higher than the crop needs (Kumar et al., 2005). It is recommended that manure and biosolids application rates be based on the nutrient requirements of the intended crop so as to minimize the unintended introduction of these micropollutants into the food chain at levels that can be avoided. 

Increasing the rate of nitrogen fertilizer application affected the relative proportions of some of the essential oil components (Martin et al., 1985). At higher N rates, limonene and other monoterpene concentrations decreased to very low values, while those of sedanolide and phthalides increased to above 75% (D Antuono et al., 2002). 

Chemical fertilizers are used in most parts of the world, although less so in developing countries because of the high cost. The nitrogen content in chemical fertilizers is known, and application rates can be determined accurately, These may vary depending on the cropping system used. Nutrients are more immediately available for plant uptake in chemical fertilizers than in manure however, they may be more easily leached into groundwater if used in excess. Slow-release fertilizers reduce this loss,... 

Few papers have been published on the effects of radioactivity in P fertilizers on agricultural crops. Winter wheat grain and straw were analyzed for Ra after plots were fertilized annually with P fertilizers for 11 years in Belgium (Kirchmann et al., 1980). Total P application rates for this 11-year period were 153 and 597 kg ha" which could provide mean annual rates of 14 and 54 kg P ha", respectively. They reported no... 

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