Plant tissue analysis is a nutrient management tool that has been around for a few years, but as more farmers and agronomists realize the valuable insights it can provide, its use is growing among both these groups.
Why it matters: More farmers and agronomists are using multiple in-season tissue test results to optimize fertility programs.
“Tissue testing is not new, but interest in it is increasing as another way for producers to make sure they’re optimizing inputs to get their highest yield possible,” explains Nevin McDougall, president and chief commercial officer at A&L Canada Laboratories in London, Ont.
“In addition to other tools, tissue testing adds a further dimension for farmers to make the best decisions about in-season fertility. Most crop farmers are moving past the point where they plant seeds in the spring and only look out for disease and pest issues during the growing season. There is a lot of opportunity to also better manage fertility during the summer to ensure maximized profits.”
The other tools used to make in-season fertility decisions are generally field scouting and results of soil tests done the spring or fall before. McDougall says some progressive farmers in Canada and around the globe also use normalized difference vegetation index (NDVI), which measures plant health based on how the plant reflects different wavelengths of light, measurements from UAVs and satellite imagery. On large-acre farms, he says, there is a place for NDVI to show where a crop is achieving higher and lower productivity, and this narrows down the areas of the farm where tissue testing is most effective.
However, for any amount of acreage, a crop with high-yield potential may run out of certain nutrients — or may be approaching that critical line — faster than farmers had anticipated, due to new genetics, exceptional growing conditions or a combination of both. That’s why several years ago, laboratories started offering programs that help farmers check their plant nutrient levels at critical crop growth stages. Tissue testing at those stages can identify both existing fertility problems and potential fertility problems before physical symptoms of deficiency are present (at which point yield can already be affected). Tissue testing can also validate recommendations made by agronomists, giving them the assurance that they are providing accurate guidance.
When, where and how often
McDougall recommends starting with one sample per 25 acres, but the appropriate number of samples is dependent on field size and degree of variability across the field. When to sample is also dependent on several factors, such as geography, field size and yield goals. Some growers may be aiming to compare different fertility programs or drive a crop to its highest achievable yield and quality by top dressing or adding foliar nutrition.
“Even one sample tested in late June is valuable, but if you take samples at three points in the season, you can really see how nutrient uptake is happening and because you get your test results back very quickly, with us within 24 hours of sample receipt, and you can take action immediately with a foliar application. When the results don’t indicate immediate action is required, you or you with your agronomist have the opportunity to accurately look at the costs of fuel and fertilizer versus potential yield/profit gains of various levels of applications of various nutrients,” says McDougall.
McDougall believes that multiple in-season tissue tests will become standard very soon. “If you look at innovation that is being brought into agriculture, the genetic advances, seed treatments, seed placement and so on, things are continuing to advance and improve,” he says. “Management of fertility must keep up.”