SPADA Draft Documents

Composite samples are those that are comprised of a number of smaller samples 361 mixed together in order to reduce the cost of analyzing each sample individually. For 362 example, random samples collected within a sub-area can be composited and analyzed to 363 produce a single result for that sub-area. Once prepared, the composite sample can no 364 longer provide any information on the variation among the individual samples. In order 365 for results from composited samples to be valid, certain conditions must be met. First, all 366 composite samples should be comprised of an equal number and mass of individual 367 samples; second, there must be no interactions between the individual samples as these 368 interactions could skew the results; and third, the study’s objectives must include 369 obtaining an unbiased estimate of the mean (8). 373 analyses, the typical protocol is to air dry the soil for several days or place the sample in a 374 drying oven at 105°C overnight. After removing rocks and plant debris, the dried sample 375 is then crushed with a mortar and pestle and passed through an American Society for 376 Testing and Materials (ASTM)-compliant 2 mm standard sieve to remove gravel. This 377 protocol is not appropriate, however, for maintaining the microbiological integrity of the 378 sample. 379 If a soil sample is collected in order to retain the soil fauna, then it is recommended 380 that the soil be stored on ice immediately after collection and analyzed as soon as 381 possible. Evidence suggests that drying of the soil or long-term storage, even at 4°C, can 382 result in changes to the soil fauna (8). The soil moisture level should be measured at the 383 370 371 372 8.5 Soil Processing Soil processing is experiment-dependent. When a soil is collected for chemical

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