Sampling & Preparation:
Representative sample is essential if analytical data are to be meaningful. The samples must be also homogeneous. The necessity for consideration of homogeneity increases as sample size for analytical procedure decreases. To assure homogeneity samples are usually dried and ground prior to analysis. In case of liquid samples, samples are collected in new or acid washed glass polythene bottles. They should be analysed as quickly as possible. If immediate analysis is not possible samples can be preserved for Kjeldhal digestion by acidifying to PH 1.5 to 2.0 with concentrated sulphuric acid and storing at 4°C. For analysis of Nutrients in plant materials previous wet digestion of sample is recommended. Rapid changes in the nitrate and ammonia contents of soil samples occur after removal of the samples from field or pot, because of the increased aeration and rise in temperature. It is, therefore, desirable that the extraction of nitrates and ammonium follow the collection of the samples closely.