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The alkaline permanganate digestion method has been widely used for assessing the available nitrogen pool in soils. We report that simple laboratory experiments have shown that the standard method does not include nitrate and nitrite, but that a simple modification, involving the use of Devarda's alloy, allows inclusion of nitrate and nitrite. This modification is desirable if the method is to be used for assessing available nitrogen in tropical upland soils that experience pronounced wet and dry seasons. Results with soil on our experimental farm showed that the nitrate content of the soil contributed 10 to 40 percent of the available nitrogen assessed by the modified method.
Sahrawat et al. (Fri,) studied this question.