It's Time for an Annual Plant Tissue Exam
 

You can't tell what your cholesterol levels are by looking in the mirror. Visual observations can offer some hints of overall physical fitness, but the only way to really know your cholesterol levels requires blood work at the doctor's office. Your crops all need the same type of attention in order to remain healthy until harvest. Get the results you need using tissue testing.

Spend time walking through different areas of your field. Nutritional deficiencies or toxicities exhibit signs you cannot see from the window of your truck, while driving on the road, so get out and look closely. Often, by the time you see a problem the crop has already been affected. Many nutrient problems look similar to disease or insect problems. 

Tissue testing is a very useful laboratory test that can be used to determine nutrient status. Tissue testing for any type of plant can be done at AgSource Laboratories in Bonduel, Wis. Corn, soybeans, alfalfa and potatoes are the most common plants analyzed, but virtually any plant tissue can be tested. A pictorial plant sample guide can be found at plant-tissue.agsource.com.

A tissue analysis provides you with the concentrations of individual nutrients found in the growing crop sample. You can determine what nutrients are low even before the plant shows visual symptoms and decide if additional fertilizer is needed. Save money on fertilizer by focusing applications where they are needed most.

Typical plant tissue analysis will test concentrations of nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, manganese, zinc, copper, iron, sodium, aluminum, and boron.

When to Sample: Proper sampling is a key to reliable test results. To monitor plant nutrient status most effectively sample during the recommended growth stage (see chart). Make sure to take additional samples weekly or biweekly during critical periods. It is also important to sample the proper plant part.

Crop Sampling Chart

Crop	Time	Method of Sampling	# Of Plants to Sample
Corn	Prior to 4th leaf stage	Collect whole plants, cutting at ground level	30
Corn	Prior to tasseling	Gather the whole leaf immediately below the whorl, removing at the stalk	20
Corn	At silk when silks are still green	Gather the entire ear leaf, removing at the stalk	20
Soybeans	Prior to 8" tall	Collect all above ground portion	25
Soybeans	At initial bloom	Collect trifoliate leaves, one trifoliate set per plant. Remove the leaf petiole	25
Small Grains	Prior to heading	Remove upper 6" of the plant, leaves only	35
Cotton	At full bloom	Select youngest recently matured leaves on the male stem, collecting 2 leaves per plant	25
Alfalfa	Prior to or at bloom	Collect top 6" of plant	30
Forage-Grasses	For maximum quality hay	Remove top 6" of plant.	50
Tobacco	Prior to or at bloom	Take the entire 4th leaf from the top of the plant	15
Grain-Sorghum	Prior to or at heading	Submit second leaf from the top of the plant	25

Size of Sample: The proper amount of plant material to collect depends on the crop. It is better to send too much material rather than not enough. Use a zigzag pattern to get a random and representative sample. Do not collect insect or disease damaged plant parts. Often it is helpful to submit plants from a healthy looking area and compare them to a sample of plants from an area of concern. Analyzing a soil sample from each area is also helpful for troubleshooting.

Clean off any dirt from the sample and put in into a clearly labeled paper bag. Include the field identification, type of crop, plant part collected, number of samples, and appearance of the plant. Do not use any plastic as this will promote molding. Collect and mail or deliver samples to the lab early in the week. 

Results: The AgSource Laboratories report will indicate if nutrients in the tissue are deficient, sufficient or high. To best understand your tissue results, review results of tissue and soil together.

Conclusion: If you think tissue analysis might benefit your crops this year, contact your cooperative or crop consultant, extension expert or AgSource Laboratories to request sampling supplies. Professional laboratory analysis of plant tissue can help you utilize resources more wisely and enjoy a more fruitful harvest.

AgSource is a leader in agricultural and environmental laboratory analysis and information management services. A subsidiary of Cooperative Resources International, AgSource provides services to clients in the United States and across the globe. Learn more at www.agsource.com.