AGRONOMIC NEWS ITEMS
From Agronomists of the
Potash & Phosphate Institute
655 Engineering Drive, Suite 110
Norcross, Georgia 30092-2837
Phone (770) 447-0335
Summer 1998, No. 6
There are many other factors besides soil fertility that can influence plant nutrient uptake efficiency of both soil and applied nutrients. Some of them are: Soil compaction, root pruning with tillage, low soil temperature, soil moisture, drought, pathogens, nematodes, insects, tillage, herbicide stress, and unfavorable soil pH. To maximize the probability of reaching the expected yield goal, through balanced fertilization, these other factors must also be considered.
Plant tissue analysis is an excellent way to evaluate the success of the nutrient management program, because the plant integrates all the factors that have interacted to affect growth and development. Plant tissue samples collected during the early season, can be used to diagnose nutrient imbalances in time to take corrective action. Many experienced crop consultants use plant tissue analyses as an in-season guide to monitor plant nutrition and to recommend additional nutrients such as nitrogen, potassium, sulfur, zinc, and boron. If identified early enough, phosphorus fertilization may also be recommended to correct deficiencies.
Proper interpretation of plant tissue analyses depends on appropriate and representative sample collection. Most laboratories can provide specific sampling guidelines for different crops. In addition to giving instructions on how to take the samples, they usually recommend; 1) that samples be free of surface contamination; 2) that samples be placed in paper bags (not plastic); 3) that samples be quickly dried to stop enzymatic reactions and to prevent spoilage in shipment, and 4) that samples be shipped as rapidly as possible after collection.
The goal of plant tissue analysis is to intercept problems or accurately diagnose them in time to correct them in the current crop or before the next crop in rotation. If plants suffer to the point that they exhibit nutrient deficiency symptoms, some yield has probably already been lost. However, if detected in time, corrective fertilization can help avoid economic yield losses.
Arkansas research showed that potassium application prior to early soybean pod development increased yields by more than 8 bushels per acre, after plant tissue and soil analyses confirmed a deficiency. In this particular study, adequate moisture was provided through irrigation for the remainder of the growing season, after corrective potassium fertilization. It should be pointed out, though that final yields would have been much greater if adequate potassium fertilizer been applied pre-plant. In-season fertilizer to correct deficiencies is never as effective as is following recommended practices.
Consider plant tissue analysis in 1998 to better monitor the performance of your nutrient management program. It's a valuable tool that can verify the success of a fertilization program or detect weaknesses for corrective action.