Wednesday, April 04, 2007

From Seed to Salad: the Path of Specialty Lettuce

Our Specialty Lettuce greenhouse functions much the same way as our Boston Lettuce operation, except that right now it will take forty days to go from seed to salad, using the Controlled Environment Agriculture model.

This tried-and-true system was designed by a professor at Cornell University—in upstate New York—in order to be able to bring crisp, crunchy lettuce to your table year round.

The Cornell model produces 1,000 heads of lettuce per day. Our more modest operation on a slightly smaller scale will have an output of 600 heads of specialty lettuce each and every day, 365 days a year.

A special area of our 5500 square foot greenhouse is dedicated to seed germination. An automatic seeding machine places one seed each into 10 plug trays of 100 plugs each. (The reason we start off with 1,000 potential plants, instead of 600, is to allow for attrition and the selection process that takes place later.)

The trays are misted with water to soak the media thoroughly then they are placed in the ebb and flow bench. Here they are periodically flooded with a very mild solution of Advanced Nutrients Scorpion Juice (to impart induced systemic resistance to pathogens and pests), as well as Organic B, which gives them a boost of B vitamins for stress relief.

This sub-irrigation is only for a quarter of an hour, every 12 hours. It is important not to over-water the trays at this point, but the plugs should not be allowed to dry out completely either, since that will also kill the seeds.

Lighting is provided by fluorescent tubes and is on 24 hours, at the strength of 50 micromoles per square meter. The temperature of the germination room is set at 20º C (68º F) and the seed trays are equipped with plastic humidity covers to maintain the high level of humidity required for germination.

A half-strength solution of our base fertilizers (Grow and Micro) is added to the sub-irrigation water 24 hours after sowing. The EC of the water is set at 1.71, or 1200 ppm. The pH is adjusted to 5.8 pH, with the possible addition of Advanced Nutrients pH Up or pH Down.

Since the day of sowing is considered Day 0, this is actually Day 1. The temperature is raised to 25º C (77º F) and the lighting is increased to 250 micromoles per square meter. Sub-irrigation continues for 15 minutes every 12 hours, for the first six days.

The humidity covers are removed on Day 2. The seeds have germinated (hopefully) and the radicle root has started to penetrate the soil of the plug. The high humidity levels for the first two days of seeding were maintained to ensure that the seeds would not dry up. This is also why low light levels were maintained during day 0.

No matter how accurate the seeding machine is, double seedlings are sure to happen, so on Day 3 these are removed to guarantee a uniform crop. Consistent environmental conditions are absolutely essential at this stage.

Seedling selection takes place on Day 5, and this is a labor intensive process. Seedling are judged by the size of their first leaves. Those inordinately large, as well as those too small, are discarded. We are prepared to discard 20-30% of the seedlings at this time.

On Day 6 the seedlings have grown to a sufficient size to require more frequent feeding/watering. The ebb and flow sub-irrigation system is set to flood the trays for 15 minutes, every 6 hours (four times per day).

From Day 6 to Day 11 the seedlings are allowed to grow in the trays, with the roots coming out the bottom of the plugs. The leaves eventually start overlapping, which is a sign that it’s time for transplanting.

At this time, our seedlings are treated with No Shock and Jump Start, which are Advanced Nutrients products specifically designed to reduce the shock of transplanting and give a boost to the young plants so that they are able to thrive in a new setting.

Transplanting normally takes place right after a sub-irrigation interval, to ensure that the seedlings to not get desiccated during transfer. Also, one has to be very careful with the exposed roots.

The seedling plugs are placed into pre-cut squares in Styrofoam floaters and placed on the Nutrient Pond. The Pond contains a pre-mixed solution of our base fertilizers, Micro and Grow, as well as vitamin and growth supplements and root colonizers, that are designed to nourish each seedling so that it can grow into the healthiest, crispiest head of lettuce possible.

The ingredients in our nutrient solution include Sensi Cal Mg Mix Grow, since research has indicated that lettuce plants not only require extra Calcium to ensure that crunchy texture, but also Magnesium to facilitate the absorption of the Calcium. The synergistic effects of these two elements play a vital role in plant growth.

At this point our specialty lettuce seedlings are introduced to Piranha, Tarantula, and Voodoo Juice. No, we’re not shooting a horror movie, these are very effective root colonizers made by Advanced Nutrients.

Used at half-strength in a hydroponic situation, these phenomenally effective products permeate the roots of our lettuce with beneficial fungi, bacteria, and microbes respectively. Their presence not only ensures root growth, but it also wards off harmful fungi, bacteria, and microbes, as well as facilitates nutrient absorption.

It’s all right to use Piranha, Tarantula, and Voodoo Juice at full strength in soil, but in a hydro grow it is advisable to cut back to half the suggested strength. The living organisms in these products do their job so enthusiastically, that they might multiply so fast that your roots are overwhelmed.

We had this happen with our Boston Lettuce crop. I noticed that the roots became slick and slimy, showing symptoms of root rot. I alerted my partner, Chuck, who phoned the Advanced Nutrients tech guys immediately.

They advised us to stop adding the three root colonizers and flush to system with a weak solution of HyOx, which killed off about half of the enthusiastic microorganisms. Then we re-introduced Piranha, Tarantula, and Voodoo Juice at half the suggested strength and we had no problems ever since.

In fact, a larger healthier root system has ensured that our Boston Lettuce is consistently of high quality. We are hoping to produce our Red Sails and Green Ice specialty lettuce crops to the same high standards.

posted by silvio @ 9:03 PM   0 comments


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