Crops nutrients required

The N/P ratio was increased from 3.9 in raw manure to 5.2 in the bioreactor effluent and to 9.2 in the supernatant fraction of settled effluent. This separation of nutrients increased the agronomic value of manure as it more closely matched crop nutrient requirements. Another advantage of AD manure as fertilizer is reduction in odor, with a high mineralized N content and N P ratio, increases the window in which it can be applied to land to meet nutrient requirements at various stages of crop growth. 

Generation of data on the nutrient content of agricultural products and foods forms the basis for estimating nutrient intakes of populations via dietary surveys, nutritional labelling for consumer protection, nutrition education for consumer food choice, home and institution menu planning and food purchase, and for research in nutrient requirements and metabolism, toxicant chemical composition is used to assess effects of farm management practices, crop culture, and food processing on chemical content and implications for human health. 

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. 

Beneficial and Harmful Effects. At low levels, sulfur dioxide in the atmosphere is not harmful to crops, but damage can occur at excessive levels (305—309). Crops differ gready in their sensitivity. Forest damage attributed to acid rain is often cited but the observed symptoms seem to have multiple causes and the contribution of sulfur acids is unspecified. The sulfur in precipitation is, up to a point, beneficial to plant growth because sulfur is an essential nutrient. Lessening the sulfur content of the atmosphere requires that supplementary sulfur be provided in fertilizer to some crops some crops already require supplementary sulfur. Sulfur dioxide itself has been found useful in drip irrigation systems (310,311) and in calcareous soils (308). Small field generators have been developed for this purpose. 

POME has proven to be a good source of organic fertilizer and is available in large volume (Table 29). Applied at rates corresponding to the nutrient requirement of crops, it will not have detrimental impact on the environment. The beneficial effects of POME apphcation on crop yield and performance have been investigated. Several methods of land application systems are available. 

Byrnes BH and Bumb BL (1998) Population owth, food production and nutrient requirements. In Rengel Z, ed.. Nutrient use in crop production. 

Nutrients required by crops can be divided up into major elements and micro (trace) elements (Table 4.2). Micro (trace) elements include boron, copper, iron, manganese, molybdenum, zinc and cobalt, some of which are dealt with later in this chapter. 

While the trace-element content of guano and, to a lesser extent, of mined mineral salts, could make some contribution to the nutrient requirements of crops, these materials are no longer adequately available. We have now become largely dependent on highly purified compound fertilisers containing only nitrogen, phosphorus and potassium as nutrients, so that the rate of depletion of essential trace elements has been greatly accelerated. The natural cycle... 

It is clear from the data in Table 3 that depletion can be a significant factor which affects the ability of mineral soils to meet the nutrient requirements of plants with respect to molybdenum, boron and copper and that when the total soil levels of these elements are low, crop requirements can only be met for limited periods. For example, an acre of soil containing only 1 ppm boron cannot possibly produce more than 100 tons of crop dry matter with a content of 10 ppm boron. In practice, the boron content is likely to be around 40 ppm in the dry matter and this would limit the total possible yield on such a soil to 25 tons of crop dry matter. Deficiency conditions involving these elements are therefore inevitable within decades on cultivated land, if no steps are taken to replace cropping losses. Deficiency problems involving manganese and cobalt, on the other hand, are more likely to be due to a reduction of availability in the soil than to depletion of the total soil reserves. 

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