Starter Fertilization…In-furrow or 2×2?? (Collins & Edmisten)
Due to the widespread use of Admire Pro in-furrow for thrips control, there has been a noticeable and increasing interest in applying starter fertilizers in-furrow as well.
There are a multitude of starter fertilizer products available to growers, many of which supply both macro and micronutrients, and therefore it is nearly impossible to evaluate or discuss each one. Generally speaking, starter fertilizers applied in a 2×2 placement (2 inches to the side of the furrow and 2 inches down into the soil) can be an effective way of supplying partial nutrition to a cotton crop to suffice plant needs until sidedressing, with potential benefits including: occasional improved seedling vigor, occasional minor yield increases, and the ability to supply some nutrients more economically. General recommendations for starter fertilizer applied in a 2×2 placement, or dribbling in a narrow band 2 inches to the side of the furrow, include limiting rates to 10 to 15 lbs/A of N (10 to 13 gallons/A of 10-34-0 for example). Rates exceeding these recommendations could increase the risk of burning seedlings. It is critical that growers ensure accurate 2×2 placement and avoiding high application pressures that could cause splashing close to the furrow.
If starter fertilizers are applied in-furrow however, there are serious risks involved. These risks include salt injury and ammonia toxicity. There have been several cases in which growers applied starter fertilizer in-furrow and did not observe any adverse effects from such. However, there have also been other cases in which growers and researchers encountered serious problems with seedling death and therefore poor stands. Predicting if and when salt injury or ammonia toxicity will occur is very difficult, but the implications are serious when they do occur, often necessitating replanting of entire fields.
Growers using Admire Pro in-furrow should realize that the boost in seedling vigor resulting from the Admire is likely greater than that from the starter fertilizer anyway. If their equipment can support both Admire applied in-furrow and starter fertilizer in a 2×2 formation, then the aforementioned risks can be avoided. However, if a grower’s planting equipment only allows for in-furrow application, and can not support additional tanks for 2×2 starter placement, then they are encouraged to only use the Admire Pro in-furrow and making a separate pre-plant broadcast application of 20 to 30 percent of their total required N as determined by soil test recommendations.