Guidelines for field soil quick test

1. Collect a composite soil sample representative of the main active root zone of the crop. Don't include the top 2 inches of soil, since it may be high in nitrogen but too dry for active root growth. Blend soil thoroughly in a container.

2. Fill a volumetrically marked tube or cylinder to the 30 milliliter level with 0.01 M calcium chloride solution (about 1/4 ounce per gallon of water). The calcium will help the soil settle to the bottom of the tube.

3. Add field-moist soil to the tube until the liquid level rises to 40 ml. Cap tightly and shake vigorously until soil is thoroughly dispersed. Let the tube sit until soil settles.

4. When the soil solution is reasonably clear, dip a nitrate test strip (i.e., EM Quant nitrate test strips for 0-500 ppm range) into the solution, shake off excess solution and wait 60 seconds. Estimate the nitrate concentration using the color chart provided with the strips. The test strip chart gives the parts per million of nitrate nitrogen in the solution. To convert to ppm nitrate for dry field soils, divide by the appropriate correction factor (see chart below). Correction factors for container soils have not been determined.

Soil nitrogen requirements for field-grown cut flowers should not be much different than the nitrogen needs of many field vegetable crops. For vegetables 10 ppm nitrate is low. Levels above 20 ppm nitrate are adequate to meet immediate crop needs. A low soil nitrate level late in the production cycle may not indicate insufficient nitrogen, rather it may indicate highly efficient plant uptake. Use tissue testing to confirm low nitrogen status. Tests should be conducted every two weeks for fast-growing crops and every four weeks for slow-growing crops.

Soil texture	Moist soil	Dry soil
Sand	2.3	2.6
Loam	2.0	2.4
Clay	1.7	2.2

© 2001 Branch-Smith Publishing