It’s time to review your pepper fertilization program

Adequate plant growth prior to fruit set is important for economic pepper production. If you’re fertilizing to maintain plant growth and good size fruit, you will also have to stake and tie to maintain quality.

Double row, staked and tied peppers. Photo by Ben Phillips, MSU Extension.

Double row, staked and tied peppers. Photo by Ben Phillips, MSU Extension.

There are probably as many pepper fertilization programs as there are pepper growers, and that’s OK. However, there are some things to remember no matter who designs the program. According to Michigan State University Extension, most fresh market peppers are currently grown using plasticulture techniques, including fertilizing through the drip system. There are two basic aspects that should be followed when fertilizing peppers: staking and tying, and nitrogen.

Staking and tying

Unlike their relative the tomato, peppers will respond to more nitrogen by producing more fruit – at least to a point. Peppers can be over-fertilized, which can delay flowering and fruiting. However, with good rates and timing, more nitrogen can translate to more fruit and thus, higher yields. The problem with more fruit is the pepper plant is not capable of staying erect with the extra fruit load. The plant will fall over, potentially exposing fruit to sunburn and placing it in contact with the ground or plastic, reducing quality.

If growers increase fertilizer rates, especially nitrogen, it is important they stake and tie so plants stay erect. Peppers on plastic are generally planted in two row beds. Some growers stake and tie each row, similar to a single row of staked tomatoes (see photo). Other growers will place stakes in each row, but only put the string around the outside of the two rows, keeping the peppers from falling into the walkway but allowing them to support each other between the two rows. Either way keeps the plant fairly erect – protecting the fruit.

Front load nitrogen

What I mean by front load nitrogen is that it is important to apply most of your nitrogen prior to first fruit set. Many annual fruiting plants like peppers will slow vegetative growth once they set fruit. The plant’s main goal is to make fruit and once that fruit is set it gets the idea that its job is done and shifts energy from plant growth to fruit growth. That may be good for that one fruit, but as a grower you need to have more than one marketable fruit per plant.

I’m sure you have seen pepper plants that look like sticks with a dozen leaves and two or three fruit. To avoid this, enough fertilizer has to be applied prior to fruit set so sufficient plant growth is produced prior to adding a fruit load. Once a larger plant is produced, it has enough leaf area (energy producing area) to carry a fruit load and continue vegetative growth.

I am sure many pepper growers have noticed their pepper plants put on new growth after first harvest. That’s because an energy sink (fruit) has been removed and freed up energy to allow the plant to shift it to making new vegetative growth. The goal is to get enough plant growth initially so these growth starts and stops are minimized.

Actual nutrient amounts vary from site to site and plant population, but for most situations all phosphorus (P) and potassium (K) can be broadcast prior to bed formation and planting. Nitrogen (N) should be split with part applied as a broadcast and the rest through the drip system. With this approach for N, I recommend applying 30 percent pre-plant as a broadcast, and then beginning two weeks after planting apply 45 percent of the N through the drip system spread out over the four or five weeks until the first fruit begin to swell. The final 25 percent is a maintenance level and should be spread out and applied on a weekly basis through the drip system until two weeks prior to last harvest. This approach will develop enough plant prior to fruit set that will allow the plant to continue to flower and size fruit.

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