This is the VOA SpecialEnglish AGRICULTURE REPORT.
Increasing levels of carbon dioxide gas in Earth’s atmospherehave been linked to warming of the Earth. Now, American scientistssay the rising carbon dioxide levels can interfere with the abilityof plants to use some forms of the important element nitrogen. Theysay the higher levels of carbon dioxide have affected plantseverywhere and are forcing changes in the use of agriculturalfertilizer.
The Proceedings of the National Academy of Sciences reported thefindings.
Carbon dioxide levels in Earth’s atmosphere have increased morethan thirty percent during the past two centuries. For years,scientists believed that rising levels of the industrial gas wouldhelp plants. Carbon dioxide is necessary for photosynthesis, theprocess in which green plants use sunlight to make energy.
However, recent studies found that plants cannot support theincreased amounts of carbon dioxide. In experiments, scientistsincreased carbon dioxide levels by as much as two-hundred percent.At first, the plants used thirty percent more carbon. Yet a shorttime later, the rate of carbon processing dropped to just twelvepercent greater than normal.
Scientists at the University of California at Davis are studyinghow plants react to fertilizer products made with nitrate andammonium. Nitrate and ammonium are different forms of nitrogen.Nitrogen is necessary for production of proteins and nucleic acidsin plants. Many farmers add nitrogen-rich fertilizers to theircrops.
In the new study, the scientists found that ammonium fertilizeris more effective than nitrate fertilizer when carbon dioxide levelsin the atmosphere are unusually high. The scientists grew wheatseedlings with either nitrate or ammonium under different levels ofcarbon dioxide. They found that increased carbon dioxide levelslimited the processing of nitrate in the plants.
The scientists also found that the kind of nitrogen did notaffect wheat growth when carbon dioxide was at a normal level.However, this changed when they increased the gas to almost twotimes the normal atmospheric level. The seedlings treated withammonium grew at a faster rate than those treated with nitrate.
The scientists say they had similar results using tomato plants.
This VOA Special English AGRICULTURE REPORT was written by GeorgeGrow.