Branching out with Brassicas - Summer trial in NFT production in Ohio

Branching out with Brassicas

Summer trial in NFT production in Ohio

Natalie Bumgarner, PHD

Introduction

In the greenhouses that I visit and crops I discuss with growers, it is clear that lettuce still fills a majority of plant spaces in the NFT system. However, we field an increasing number of questions about the many other leafy crop possibilities. Many of the other leafy options are in the Brassica family - cabbage cousins, essentially. These include kale, mustard, mizuna, and pac choi most commonly.


These options present growers a chance to diversify to attract new customers as well as provide more product to existing customers. One of the challenges with any new crop is understanding its production capacity to assist in pricing and tailoring production to anticipated demand. Also, there is the potential for higher light and temperature to negatively impact quality in the summer as is the case for some lettuce and other leafy crops. This trial was designed to evaluate a selection of Brassica crops as well as amaranth (not a Brassica, by the way) under summer conditions. Rather than extensively trialing multiple cultivars of the same crop, the goal was to evaluate production capacity and crop quality of a selection of alternative leafy crop
options to lay a broad foundation for future work.

Methods and Management
Seeding was done by hand into pre-moistened cubes. Three media were compared in this trial- rockwool (25 x 40 mm), Oasis (162 count Horticube XL), and a peat media (162 count, Grow-Tech). Seeds were germinated in clear water in seeding trays, and were transferred to the nursery and nutrient solution 3 to 5 days after seeding. Seedlings were produced in flowing nutrient solution in the nursery for an additional week to two weeks before transplanting (no supplemental lighting was provided during the seedling phase). After transplanting, plants were grown out in the channel until harvest. The nutrient solution was continually cycled through the Fertroller where automatic pH and EC adjustments met programmed solution set points. The pH was maintained at 5.8 by the addition of dilute sulfuric acid. EC was maintained at 1.7 to 1.8 by the addition of concentrated fertilizer solution and source water.

* This trial measured single harvest yields to produce the most accurate and comparable yield totals. However, some growers may harvest single leaves or leaflets from kale or amaranth plants. This could increase the total yield per plant but require additional time in the channel and quite honestly make comparisons much more challenging.

Timing and Conditions

Biomass Yield

* Amaranth was seeded with multiple seeds per cube as is typical in production, but this increased the yield variability.

Some thoughts on the trial

After considering these trials, there are a few things that I would like to bring up for discussion.

• First, I should report that there were very few quality issues with any of these crops in these trials. They grew through the OH spring and summer conditions quite well with no losses or issues to speak of.
• Second, and most clear in the data, we can see that the yield potential of these crops is wide ranging. That is really an understatement. In fact, we had to use two different scales to weigh these trials. Besides our scale challenge, there are two key grower impacts. One is the fact that timing of transplanting and harvest really should be varied. The kale maybe could have been grown a bit longer and the WinWin Choi should have been harvested earlier for highest quality. The other important point is that it will be important for any grower going into sales with such crops to do a few trials before setting prices. We can often count on bibb lettuce to finish out at predictable weights at predictable times, so prices can be set and costs calculated simply. When selling and pricing kale, pac choi and the like, be aware that yields and therefore input costs per weight of produce vary. Don’t undersell yourself early in the process of growing a new crop.
• Thirdly, the impact of our different growing media was not clear in these trials. This is certainly my least favorite point as unclear results frustrate every researcher. In looking at the yield trends between the two runs, the differences (or lack thereof) between rockwool, oasis, and the Grow-Tech cubes were not consistent. In run 1, the peat cubes tended to perform better while that was not seen in run 2. Environmental conditions were reasonably consistent in these two trials, so that is unlikely to be the primary cause for these inconsistencies. I am hesitant to draw too strong a conclusion about this on early trials, but I will say that it may be differences in germination speed, moisture content (and therefore fertility), temperature and the like early in crop growth that led to these variations. We generally deal with pelleted lettuce seed that produces very consistent germination and early growth. Because these Brassica crops are not bred for controlled environment production, their response to small differences in conditions may not be as well understood at this point in time. More focus on the seedling aspect may well be needed.

Notice the difference in germination rate and seedling size between the five crops in this trial. Tiny amaranth seedlings are in the back of the tray.

Plant Images from Run 1

Toscano Kale- At harvest (44 days after seeding)

Red Giant Mustard- 44 days after seeding

Red Choi- 44 days after seeding

WinWin Choi- 44 days after seeding

Red Leaf Amaranth- 44 days after seeding

2014 Tomato Trials- Summer Sneak Peak

2014 Tomato Trials- Summer Sneak Peak

Natalie Bumgarner, PHD

Trial Overview

For many of the producers that we serve, beefsteak tomatoes are a large majority of their production. However, trends in consumption and competition are increasing interest in specialty cultivars. From demand for farm to school salad bar items to farmers market mixed baskets, there are a range of options for small fruited and colored tomatoes. While visual interest and taste are critical in these cultivars, it is essential that production be adequate and relatively consistent over the season. These two questions are the reason behind this trial. Exhaustive yield data is not possible on the scale that we trial in our test greenhouse, but early evaluation is essential to begin to make suggestions for growers. So, this evaluation was carried out on small plots of fifteen cultivars to assess plant production throughout the season. These are preliminary trials to determine what cultivars to trial more extensively in the future.

Plant Management

•All ungrafted seedlings transplanted from 1.5” rockwool cubes into perlite filled Bato buckets
•Plant density was 4 ft2 per plant or 2.7 plants/m2
•Began feeding seedlings at 1.5 mS/cm EC and increased feed to 2.2-2.4 mS/cm as mature plants
•Target leach ECs were 0.4-0.6 above feed ECs (2.6 to 3.0 mS/cm)

Italia- Roma

Itaca- Roma

Prunus- Roma

Colored Plums

tiger plum

small pink

Dasher

0603

72-163RZ

Zebrino

Cantina Purple

Vacetto

Orange

DRC-564

Dealing with a Rexless Summer?

Dealing with a Rexless Summer?

2013 data to the rescue

by: Dr. Natalie Bumgarner

Introduction

For growers, there exists something of a codependent relationship between them and their cultivar of choice. Due to uncertainties in seed production and demand, there is always the possibility of seed shortages or movement by the industry away from the ‘old faithfuls’. For bibb growers, the popular cultivar Rex is likely going to be less available this summer and early fall and so the questions of what other options to grow certainly are coming to our attention. While it is never possible to guarantee other cultivars will seamlessly replace current ones, CropKing’s trialing and research program is carried out to assist decision making in these areas. So, the best way for me to help growers decide what to grow is to show you what I have observed and measured in our greenhouses here in Lodi.

Data from Fall 2013 Bibb Trial

•Trials were carried out to test four similar green bibb cultivars in three different growing media
1) 1”x1”x1.5” Grodan rockwool , 2) 162 count Oasis XL, 3) 128 count trays of Grow-Tech peat- based media (http://www.grow-tech.com/)
•Time to harvest was varied through the season to produce marketable heads under changing light regimes

Alexandria

Run 4

Run 1

Flandria

Run 4

Run1

Gardia

Run 1

Run 4

Natalia

Run 4

Run 1

Investigating impacts of Electrical Conductivity in Nutrient Solutions

Investigating impacts of Electrical Conductivity in Nutrient Solutions

Lettuce and Brassica winter production in NFT systems in Ohio 

By: Dr. Natalie Bumgarner

Introduction

In recirculating systems producing leafy crops, one of the main factors in the control of the grower is the nutrient solution electrical conductivity (EC). In many systems, total EC, rather than single elements are controlled due to economics. In most commercial systems using electronic controllers and dosing pumps, concentrated fertilizer solution is added to the nutrient solution any time the solution goes below target EC. So, maintaining consistent EC levels is fairly straightforward, the main question becomes: What is the best EC? The answer to this question is based on two separate factors. The first relates to maintaining needed nutrients in solution. Essentially, the important question is how close to calculated nutrient levels does the solution remain over time. If there are large amounts of ions already in the source water (sodium, sulfate, or calcium for instance), this can cause the nutrient solution to become out of balance more rapidly meaning that ideal ratios of nutrients are not maintained. The second factor involves the movement of water through the plant. At lower EC, it is easier for plants to take up and transpire water. Therefore, under high light and temperature, and low humidity, lower solution EC levels makes it easier for the plant to move water. So, the EC that we use in our systems needs to address these two issues: 1) Maintain adequate levels of plant nutrients, and 2) not stress the plant too much in terms of taking up water needed for transpiration.

Plant Management

Seeding was done by hand into pre-moistened 1” x 1” x 1 ½” cubes. Seeds were germinated in 9” nursery channels that were receiving a continuous flow of nutrient solutions set at experimental levels. After 15 to 17 days, seedlings were transplanted to the production NFT channels at a spacing of 8” on centers. After transplanting, plants were grown in 4 ¾” channels until harvest. The nutrient solution was automatically and continually adjusted to maintain a target pH of 6.0. Electrical conductivity was maintained by hand additions of nutrient concentrate as 

needed based on daily measurements of EC. These trials were carried out in a system designed to pull from four different 40 gallon nutrient tanks so that differing solution could be tested in a randomized block design. At harvest, shoot fresh weight was recorded individually for each head.

Timing and Conditions

* 400W metal halide lights were used to add approximately 30-40 µmol/m2/sec of supplemental light from 4 to 11 am during the lettuce experiment, but power usage constraints prevented lights from being used during the Brassica trial.

Biomass Yield by EC Treatment

Letters signify differences between EC treatments across all three cultivars. Treatments are only significantly different if followed by different letters.

EC x Cultivar Biomass Yield

Discussion on the two trials

These two runs of a fairly straightforward nutrient concentration test reveal some interesting results and, as useful tests should, provide some additional questions for future work.

1) Under the conditions of these trials, it is quite possible that nutrition was not always the most limiting factor. Yields were statistically similar in the lettuce trial for treatments where 1.3, 1.8, and 2.3 EC was maintained. This would suggest that all three of those EC treatments provided adequate nutrition and that the generally low yields in the trial, may have been due to low light conditions. Many times growers increase EC during the winter to push growth. Certainly under some conditions, that can be a valid technique, but it is also possible that the plants may not be able to parlay those available nutrients into increased yield. It should also be stated that our nutrient targets for recirculating systems are purposefully determined in excess of minimum nutrient levels to provide buffer in our systems and prevent yield reductions.

2) For some cultivars, quality impacts can be as large a determining factor in nutrient solution adjustment as yield. For any grower who has tip-burned romaine lettuce (and that includes a high percentage of those who have grown it), it comes as no surprise that quality issues are often more prevalent than in bibb lettuce. For some of our crops, then it may be maintaining crop quality rather than growth rate that is the determining management factor. So, if tipburn increases to a costly level, we may run lower EC even if slightly higher levels would lead to increased biomass accumulation. We also need to investigate other aspects of our management (air circulation, lighting, cultivar selection, etc.) to make sure that it really is a nutrient issue causing our decreased quality. This leads into many separate areas of research, but it is important to remember that only one of the lettuce cultivars and none of the Brassicas sustained tipburn in these trials.

3) For leafy crops other than lettuce, there still is likely room for improvement in our plant nutrition and crop management. Earlier in the discussion, I mentioned the fact that the clearer separation between EC treatments in the Brassica trial may have been due to less frequent tank changes and more opportunity for nutrient limitation in the 1.3 and 0.8 EC treatments. That is possible, but it is also quite possible that kale, arugula, and pac choi may have different optimum nutrient levels than lettuce (or each other for that matter). For the past several decades, bibb lettuce has been the focus of most hydroponic research and with an increase in the number of profitable crops that can be grown in greenhouses, it is quite possible that we still have a bit to learn about these other crops.

So, what are the questions for follow up trials??

1)How do seasonal conditions impact tests such as these?

As discussed earlier, both of these trials were carried out in low light, winter conditions. It is quite likely that when light is less limiting that more nutrition impacts will be present. Likewise, quality impacts (tipburn) may be more of a factor in summer trials.

2)What about the impact of the frequency of tank changes?

In most of our recirculating systems, our goal is to manage solutions to prevent nutrients from becoming limiting. Tank changes at specific intervals are often how we accomplish this goal (without purchasing specific ion probes). Only through nutrient testing and trials will we know for sure what the optimum EC and intervals between solution changes will be. While it stands to reason that tank changes may need to be less frequent at higher EC levels and/or higher light conditions, we need data to back up our practices and theories.