The rate of conversion increases as the soil temperature increases. Once the soil sample is collected its temperature is greatly influenced by the surrounding air temperature. The purpose of the PSNT is to determine the available nitrogen status at the time the soil sample is collected. It is therefore desirable to minimize the amount of microbial activity after the soil sample is collected. Keep the soil sample in as cool an environment as possible until it can be rapidly air dried.
Researchers store samples in a cooler containing ice.
Laying the samples on the ground in the shade helps keep the samples near soil temperature. Do not leave the samples in direct sun while in a container. The worst situation is to have samples in plastic bags in the hot cab of a pickup or trunk of a car on a sunny day. Soil samples for nitrate testing should be dried as quickly as possible. After thoroughly mixing a sample spread out about a pint of the soil in a thin layer to dry.