The early-planted Mississippi corn crop is approaching tassel, which signifies the beginning of the important reproductive stages. Additionally, the weather has been fluctuating widely over the past several weeks, presenting challenges to producers attempting to complete management practices. Therefore, how may these factors affect mid-season application of various inputs, including nitrogen fertilizer, foliar fungicide, or other products? The realistic corn response to specific application timing may vary considerably depending on the current crop status and corn growth stage.
Corn physiological sensitivity to stress, photosynthetic capability and plant response to other limitations certainly varies with growth stage. Early reproductive growth stages, particularly during and shortly following pollination are the most sensitive to limitations, and as plants mature, they generally become much more tolerant. Does this mean tassel stage is the best timing for various inputs intending to improve plant health? Not necessarily, if your corn crop is currently very healthy and there are no impending limitations threatening, you shouldn’t expect the crop to be any more responsive to management timing at this specific time or growth stage.
For example, ours and other Universities’ research overwhelmingly show automatic fungicide application at tassel stage is rarely going to improve corn yield or other plant attributes in the absence of foliar disease. The extensive data set from Mississippi is based on eight solid years of fungicide trials conducted at numerous locations in both small and large plot scenarios (with and without alleys) in the absence of measurable disease and in situations where yield was thought to be threatened by foliar disease. The larger university data set from both northern and southern universities suggests that fungicides are best used in a situation where a yield-limiting disease could potentially reduce yield. Therefore, based on years of conducting foliar fungicide trials in Mississippi, our suggestion is to use routine field scouting to monitor the corn crop for yield-limiting diseases (e.g., gray leaf spot, northern corn leaf blight, southern corn rust), and better justify fungicide use when there is a reasonable opportunity of generating a profitable response. In addition, stay tuned to regular crop updates on this blog, and monitor the movement of southern rust at: Southern Rust Observations.
The most popular topic regarding this subject is supplemental nitrogen application near tassel. Most of our early-planted corn crop will be tasseling shortly and we’ve had relatively extreme conditions leading up to tassel – earlier little rainfall, and recently frequent rainfall. These adverse weather conditions can certainly hinder the success of broadcast nitrogen application for different reasons. So should you be concerned about missing the opportunity for best response, or do you have some leeway for N application and effective incorporation of your “tassel shot?” The answer depends on the condition of your crop and what has transpired until this point. These two scenarios generally address most situations we are likely to encounter:
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