Plant growth problems

Physical foundations of SAH application seem more or less clear and have been confirmed experimentally. As for the biological efficiency in solving plant growth problems and, especially, the economic feasibility of their application, the available... 

Local county Extension offices can explain how to take a soil sample, where to send it for analysis and the nominal fee involved. Testing soil before applying lime is important becanse too much lime creates plant-growth problems very similar in appearance to too little lime. 

The difficulty in allelopathic studies has been to link the allelochemicals directly with the plant growth problems. Before the role of crop residue, soil management, or other practices in allelopathic problems can be evaluated, a direct link must be established between the source or production of the chemicals and plant damage. Plant damage may be caused by the chemicals produced from residue decomposition or from the microorganisms residing in the residues. 

As far as the effects of contamination are concerned, the main problems associated with harm to plant growth... 

Use the following general measures to encourage healthy, problem-free plant growth and reduce the need to use controls. 

Synthesis and Screening. One of the key problems for industry is the question "How does one screen for new plant growth regulants " (8). In the case of herbicides and insecticides, they either work or they don t. The field effects of plant growth regulators are harder to see, predict or test for. 

Another problem or consideration that may interfere with some aspects of allelopathy (especially in field experiments) has arisen over the past fifty years with the introduction and use of a multitude of xenobiotic compounds as insecticides, fungicides, plant growth regulators, harvest aids, and herbicides. A variety of such compounds have been and continue to be used on a world-wide scale. Some of these chemicals and/or their transformation products are persistent in soils and water. Other such chemicals are routinely applied at various times during a year. These xenobiotics may interfere or interact with naturally occurring allelochemics and thus alter or even mask certain natural allelochemical effects. Researchers will have a more difficult time to find natural areas that do not contain xenobiotic... 

At this level, ozone is a pollutant with a harsh odour. In humans and animals, it causes respiratory problems, including coughing, wheezing, and eye irritation. It retards plant growth, reduces the productivity of crops, and damages forests. Concentrations of ozone as low as 0.1 ppm (parts per million) can decrease photosynthesis by 50%. In addition, it damages plastics, breaks down rubber, and corrodes metals. 

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