Techniques of Field Sampling and Plant Analysis A field of alfalfa should be divided into two or more segments of not over 20 acres each. Sampling should be done at one-tenth bloom or when one out of 10 plants has some open blossoms. Samples should be taken by walking across the center of the area collecting one complete stem of alfalfa at 35 different locations distributed at equal intervals. The mid-stem tissue is obtained by cutting out the middle third of the stem and stripping the leaves from it. Samples should be air dried or oven dried at 158°F and ground to pass a 40-mesh screen. Analysis for acid soluble phosphorus is made as described on page 49 of California Agricultural Experiment Station Bulletin 766. A free copy of Bulletin 766 may be obtained at the local Farm Advisor's Office or by a request sent to Agricultural Publications, 207 University Hall, University of California, Berkeley 4, California.