Storage of Soil Samples and Its Effect upon the Subsequent Accumulation of Nitrate Nitrogen during Controlled Incubation
1958
Harpstead, M. I. | Brage, B. L.
Ten South Dakota soils were investigated to determine the effect of prolonged storage under air-dry conditions on the accumulation of nitrate nitrogen during subsequent laboratory incubation. Each soil was sieved and spread out in a drying cabinet where there was forced air circulation at room temperature. While the soils were still moist, as they occurred in the field, a sample of each soil was leached free of nitrate and incubated in a humid chamber for 14 days. Nitrate nitrogen which accumulated during the incubation period was determined. Similar incubations were made after soils had been stored at room temperature for 3, 6, 9, 18, 24, 34, and 50 weeks. Results showed the nitrification rate of freshly-collected soil was high compared to that after air-drying and 3 weeks of storage prior to incubation. Subsequent incubations showed a progressive increase in the nitrification level. The precision of results among replicates improved with the length of storage. Prior to 18 weeks of storage the amount of nitrate nitrogen accumulated during incubations was not correlated with oat yield responses to nitrogen fertilization. Incubations made after 18 weeks of storage, however, yielded results which correlated with the response of oats to nitrogen fertilization.
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