An article in the Winter 2017 Newsletter explained the importance of obtaining a good quality soil sample (1st step). An article in the Spring 2018 Newsletter explained the 2nd step, which is building a crop nutrition program. The 3rd step is discussed below.
The 3rd Step: Tissue Sampling
Carlos Palavicini, Sales Account Manager
After soil testing, the nutritional plant analysis is the most important tool to understand what is happening in the plant regarding the nutritional effects on its physiology. Therefore, it is critical to improving crop nutrition and yield. Only the plant analysis can identify the actual nutrient status of a plant.
The best way to take advantage of a tissue analysis is to use it to decide the next steps of a nutritional program. It's also a great tool to help us identify hidden deficiencies in the crop. Sometimes, the plant analysis is also the best way to get an accurate diagnosis of what we are seeing in the plant, since it isn't always easy to identify the real cause of a problem we have found in our crop. This is especially true when we need to be sure we are identifying a disease or a nutritional deficiency - or both.
It is important to keep in mind that the plant analysis is just a snapshot, a certain point in time, of the nutritional status of the plant. Then, depending on the crop that we are evaluating, we need to set our goal by doing the tissue test.
Because plant physiology is dynamic, it is necessary to compare your plant analysis results with what you expect to see on a plant at the same growth stage. Of course, how dynamic the physiology of the crop correlates with the type of crop, so what the plant analysis can tell us differs from one crop to another. A plant analysis is almost like a mid-year report card. how does your crop nutrition plan look, graded against the best in the class?
For intensive crops with a long season, such as greenhouse tomatoes or peppers, or open field chilies, eggplants or papayas, some growers prefer to do a plant analysis every month to ensure the plants are in shape to keep up the production.
In tree crops, we can take one to three plant analysis per year. A tissue analysis made before starting the season, in conjunction with a soil test, is the best way to determine the fertilizer program for the oncoming season. Sometimes a plant analysis before blossom can help us decide if we should do foliar application to assure the best yield, and a final analysis that will tell us how well prepared the tree is for the dormant period and the sprout time.
Row crops may only need one tissue analysis before the reproduction stage, in order to determine if our fertilizer program is in need of a correction. In this case it is very important to do it on time before our next opportunity to apply fertilizer.
If you are interested in making a full review of your crop's nutrient trends throughout the season, you may want to pull a tissue sample weekly. If you intend to establish this type of sampling, pull tissue samples from the same places in the field, at the same time each week. Nutrient levels will vary dependent on growth stage of the crop, weather patterns, and other variables. Regardless of crop type or analysis schedule, it is very important to make a plan of how many tests will be done during the season - with both plant and soil analysis.
For the results of the tissue analysis to be useful, it is necessary to use a sampling standard methodology. The sampling procedure includes the following aspects:
1. Selection of the tissue to sample
2. Sampling and
3. Preparation of samples for shipment to the laboratory
An important note: when there is an abnormal area in the field, it is necessary to take plant tissue samples and have an analysis from this area separate from the remainder of the field. It is also highly recommended to do a soil test of the same abnormal spot, in order to have as much information as possible. Having analysis of the normal and abnormal areas will help determine the origin of what is happening, and concentrate efforts to solve the problem.
Plant analysis is the best way for the crop or plant to tell us what nutrients it needs. When sampling a field, it is critical that the correct plant part and stage of growth be sampled, and of course that the lab be clearly informed of this. The lab will calibrate their testing to those conditions, thus the correct identification of which nutrients are low or high depends on accurate information provided to the lab.
It only takes about five minutes to properly pull plant tissues to send for analysis. A plant nutrient analysis typically costs about $20. The time and overall investment involved in acquiring this important mid-season snapshot of your crop is small, compared to the potential opportunity gained. Tweaking applications, finding unseen deficiencies, or pinpointing nutrient uptake trends can help dial in your crop nutrient management strategy for a better return on your fertilizer dollar.
*This article was in AgroLiquid's 2018 Summer Quarterly Newsletter.