Effect of cold stress on photosynthesis in barley Essay
Concentrated animal-feeding operations import large amounts of plant nutrients in purchased grain, forage, and bedding. They are generally net nutrient importers, because purchased inputs exceed nutrient losses from milk, meat, or egg sales. These excess nutrients accumulate in animal wastes that often create storage or disposal problems. High-density livestock operations frequently have an inadequate land base to efficiently use all the manure they generate, so there is the potential for increased risk of water contamination. As livestock operations have become larger, they have also tended to concentrate regionally, resulting in increased geographic separation between feed-grain producers and consumers. Manures are bulky products that are difficult and costly to apply and transport long distances. In some locations it currently is not economical to recycle the nutrients in animal waste, so long-term storage rather than re-use has become the solution to the waste problem. The net result is increasing transfer of nutrients from one part of the country to another and increased dependence on purchased fertilizer inputs in grain production areas (see text boxes on phosphorus flows).
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Soil pH has strong effects on the availability of most nutrients. This is because pH affects both the chemical forms and solubility of nutrient elements. Trace metals such as Fe, Zn, and Mn are more available at lower pH than most nutrients, while Mo and Mg are more available at higher pH than many other nutrients. The ideal soil pH for many crops is slightly acid, between about 5.8 and 7.0, because in that range there is well-balanced availability for all nutrients. This pH range also promotes an active and diverse soil microbial population and is a healthy range for earthworms and other soil organisms. Alkaline soil conditions reduce Fe availability, resulting in Fe chlorosis ("lime-induced chlorosis") on crops like soybeans when soil pH is above 7.2.
Use chemical fertilizers only after accounting for all organic nutrient sources to avoid overloading the system and losing soluble nutrients . For many farming systems,inorganic fertilizer will still be the largest nutrient input, but even then it is useful to think of chemical fertilizers as supplementary nutrients. When used to supplement biological nutrient sources, inorganic fertilizers can help make more efficient use of other available plant-growth resources, such as water and sunlight, by eliminating nutrient supply as the limiting factor in crop growth and yield. Chemical processes should be managed so they work together with biological processes for a productive agriculture and healthy environment.
Water is an essential factor in photosynthesis
The first step in maintaining soil fertility is to know current nutrient levels. This is accomplished by soil testing, which is an important soil management tool and effective basis for nutrient and lime recommendations. The goal of soil testing is no longer simply to find out whether the soil contains adequate plant nutrients for optimum growth. It also is a tool for determining whether nutrient levels are excessive and prone to move off-site. Soil fertility today is a social issue as well as a crop production concern.
Easy Science for Kids Photosynthesis: How Plants Make Food and Energy
While individual efforts to reduce carbon emissions are vital, large-scale changes in government policy and international cooperation are also required to effect meaningful reductions in atmospheric carbon. To varying degrees, governments around the globe have taken measures to promote greater energy efficiency, reduce use of fossil fuels, and support sustainable energy development. Some efforts are also being made, in many cases with the support of nongovernmental organizations, to curb deforestation by preserving forests and planting more trees.
Glossary of Terms: P - Physical Geography
Ca amendments can improve soil structure, but their usefulness probably has to be evaluated on a case-by-case basis. This may mean testing their effectiveness on strips in a field before making a large investment to treat the entire area. On a practical basis, it is important to remember that the formation of stable soil aggregates requires organic matter, and the presence and activity of a variety of soil organisms, not just Ca binding of clay particles. In addition, maintaining good soil structure requires soil management that avoids mechanical compaction, avoids physical destruction of soil aggregates by excessive tillage, and uses crop residue management to reduce surface crusting. Good soil structure results from the interaction of many physical, chemical, and biological factors.
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Applying gypsum, high-Ca lime, or other Ca amendments is sometimes recommended to add Ca, increase Ca:Mg ratios, and improve soil structure. Ca ions with multiple positive charges help build good soil structure by acting as "bridges" that bind negatively charged clay particles together. These "flocculated" clays are basic building blocks in the formation of stable soil aggregates. The cation sodium (Na), with a single charge, does not promote aggregation and has adverse effects on soil structure (see below). Mg ions are similar to Ca with two positive charges, but some believe that too much Mg relative to Ca forms "tight" soils due to differences in size between Ca and Mg. However, within the ranges of these the two ions commonly found in soil, there is no clear evidence for a Ca:Mg ratio effect on soil structure.