Thursday, June 12, 2014

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





Cantina Purple




Monday, May 12, 2014

Dealing with a Rexless Summer?

Dealing with a Rexless Summer?
2013 data to the rescue
by: Dr. Natalie Bumgarner


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 (
•Time to harvest was varied through the season to produce marketable heads under changing light regimes


Run 4
Run 1


Run 4


Run 1
Run 4


Run 4
Run 1

Tuesday, April 8, 2014

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


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 ┬Ámol/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.

Tuesday, February 4, 2014

Summer to Fall Mixed Leafy Trial

Summer to Fall Mixed Leafy Trial
Kale, endive, and cress in NFT production in Ohio
By: Dr. Natalie Bumgarner


While lettuce fills a large majority of the spaces in most greenhouse nutrient film technique (NFT) systems in the US, there are many other crops that can be profitable for growers in these systems. In addition to herbs, other leafy crops, such as kale, cress and endive are currently being investigated by growers to address specialty markets. In recent years, more growers are experimenting with these varied leafy crops. However, less is known about crop productivity and timing in relation to both cultivar and seasonal impacts. It is also important to note that unlike bibb and some other lettuce types, most kale, endive and cress are not specifically bred and developed for controlled environment production. So, there is a potential for greater seasonal variability in production than is seen in some of the common bibb lettuce crops. This trial was designed to evaluate a selection of kale and other leafy crops through a range of summer to fall conditions to evaluate their potential for greenhouse growers in the Midwest and Northeast. This trial obviously only used a portion of the cultivars available, but was intended to provide information for future more extensive trials.  

Methods and Management

Seeding was done by hand into pre-moistened 1” x 1” x 1 ½” cubes. 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 1.6 to 1.9 (lower light levels = higher EC) by the addition of concentrated fertilizer solution and source water.

* It is important to note that these trials were carried out across a range of seasonal conditions, so transplanting and harvesting were completed at slightly different plant ages in different runs as detailed in the next slides. Additionally, this trial measured single harvest yields to produce the most accurate and comparable yield totals. However, some growers will take multiple harvests from a single kale or cress plant, which would likely increase the total yield per plant but require additional time in the channel.

Timing and Conditions

Biomass Yield

* Watercress was seeded with multiple seeds per cube as is typical in production, but this increased the yield variability. Additionally the multiple plants grew together and created difficulty in accurately assessing yield per cube, so those comprised data are not presented, and a more upright cultivar was chosen for the next two runs of the trial.

Daily Biomass Accumulation

Some thoughts on the trial

After reviewing these data, there are a few items that are important to consider and understand about this trial.

• An important trend to note in these data is that the leafy crop cultivars in the trial did not always respond similarly to changes in seasonal conditions. Red Russian kale, which had the largest leaves and plant stature, tended to be the highest yielding kale cultivar and the yields across the first three runs were consistent. Under lower light conditions in run 4, the yield dropped to near half even with the longer production cycle. That same trend was also true for the smaller leaved Toscano cultivar. Starbor kale yields were more variable across the three first runs. In run 4, Starbor seeds could not be obtained, so Winterbor kale replaced Starbor. In future trials, it would be a good comparison to trial both Starbor and Winterbor across changing seasons.

• Seedling production was a key factor in this trial. One important note about using seeds and species not specifically bred and adapted for greenhouse conditions is that germination and early growth may be more variable than growers may be accustomed to with bibb seeds. For example, the variation between endive yield in run 2 and 3 was more likely due to germination and seedling size than to environmental conditions. The photo on the left is a close up of some of the endive seedlings in that run, and it is apparent that germination was uneven. This difference in early growth and size at transplant has a direct influence on yield in a short cycle leafy crop. The more even seedlings from another run are shown in the image on the right.

• My final comments are based on both data and observations and discussions with growers. When growing alternative leafy crops, like kale, endive, and cress, it is essential to know your market and select cultivars based on the needs of your buyers and your productivity. The cress is an example of that fact in that the highest biomass producing cultivars may have been less marketable due to their difficult to manage size. In the kale, there were large differences in cultivar biomass production and appearance. It may well be that the most desirable cultivars for buyers may not be the most productive. So, growers need to be aware of the production capacity so that prices can be properly established. This knowledge and preparation will enable growers to best capitalize on the demand for these less common leafy crops.

Plant Images

Red Russian Kale- 20 days after seeding

Red Russian Kale- At harvest (38 days after seeding)

Starbor Kale- 20 days after seeding

Starbor Kale- 38 days after seeding

Toscano- 20 days after seeding
Toscano- 38 days after seeding

Cress 38 days after seeding

Cress- 20 days after seeding

Endive- 38 days after seeding
Endive- 20 days after seeding