Cultivar Report 12.1- Butterhead Trial

Variety Trial Report- Summer/Fall 2012 

CropKing Research Greenhouse- Lodi, OH Cultivar Report 12.1

Cultivar Report 12.1- Butterhead Trial Report

Dr. Natalie Bumgarner

Objective

Hydroponic lettuce production in the United States now encompasses a wide spectrum of lettuce types and cultivars. Producers desire both attractive and distinctive crop cultivars to meet consumer demand, but consistency in both productivity and timing is still a key in the industry. Many facets of hydroponic lettuce production are impacted by seasonal conditions. One of the most important environmental impact of season is the growth rate of the plant. Growth rate is the driver of productivity and determines crop timing and the number of crops a grower can produce each year. Additionally, crop quality aspects, such as coloration and physiological defects (tipburn) are often influenced by seasonal conditions. Therefore, trialing of available varieties under differing environmental conditions as influenced by seasons are important in informing grower decisions. The goal of this set of trials was to evaluate a selection of bibb lettuce cultivars through a range of late summer to mid-winter conditions to evaluate their potential for growers producing fall to winter. Cultivars were obtained from a variety of seed suppliers to represent a broad selection of bibb cultivars available to US lettuce producers.

Materials and Methods

Plant Management-

All plants were grown for the entirety of the crop in the CropKing research greenhouse in Lodi, OH. Primed and pelleted seeds were seeded by hand in pre-moistened (with pH adjusted water) 1” x 1” x 1 ½” rockwool cubes. Seeds were germinated uncovered in clear water in seeding trays in the CropKing nursery area. Nutrient solution was added in the nursery 7 days after seeding. Seedlings were produced in flowing nutrient solution as described below for an additional week prior to transplanting. Transplanting occurred two weeks after seeding. After transplanting, lettuce plants were grown out in the channel for four weeks prior to harvest. Total production time was six weeks.

Growing System-

After transplanting, lettuce was produced to harvest in CropKing NFT channels. These 4” wide growing channels are food-grade, UV resistant PVC with matching top caps punched to fit rockwool or other similar growing mediums. Spacing for plant production is 8” within and across channels. All channels are fed by nutrient feed lines supplied a continually recirculating nutrient solution. Each channel drains into a completely closed drain line which returns the nutrient solution to the reservoir. Galvanized steel frames support the channels and the drain line. Solution is also continually cycled through the CropKing Fertroller where automatic pH and EC adjustment is carried out to meet programmed solution setpoints. The pH was maintained at 5.8 by the addition of dilute sulfuric acid. EC was maintained at 1.8 by the addition of concentrated fertilizer solution and source water.

Greenhouse Conditions-

	Air temp. average (°F)	Relative Humidity average (%)	Solar radiation average (W/m2)*	Carbon dioxide (ppm)
8/8 to 9/20 trial	70.1	81.9	141.9	461.4
9/12 to 10/23 trial	68.6	70.7	131.2	445.4

*40% white shade cloth was in place from 8/8 through 9/14 when it was removed. Thus solar radiation averages reflect reductions in light transmission provided by the shade cloth.

Nutrient Solution Formulation-

Nutrient solution was supplied by the Fertroller system discussed above. Stock solutions #1 and #2 were prepared using greenhouse grade calcium nitrate, potassium nitrate, magnesium sulfate, monopotassium phosphate, DTPA iron chelate, and CropKing MicroMix. Nutrient solution formulation was based on laboratory results from on-site samples of source was and were intended to reach macro and micronutrient targets specific for leafy crops in NFT systems.

Results

Cultivar Individual Head Wt. (g) Seeded 8/8 Harvested 9/20 Seeded 9/12 Harvested 10/23 Adriana 181±20 119±20 Alexandria 129±25 103±14 Australe 109±18 93±13 Flandria 118±17 101±8 Gardia 137±36 122±21 Hungarina 158±35 124±30 Nancy 141±20 109±15 Natalia 109±21 94±16 Red Cross 144±23 82±11 Rex 116±13 81±10 Santoro 153±18 104±13 Skyphos 74±23 58±10 Teodore 89±16 53±10

Discussion

These two lettuce crops were produced on the same production cycle with consistent days to transplant and harvest. The yield data illustrate potential seasonal effects of decreasing light as the light intensity and day length tend to decline during fall in this northern latitude. Temperature differences, even of a few degrees, in these two runs of the trial could also have influenced final harvest yields. Additionally, it should be noted that reduced biomass was more pronounced in some cultivars than other indicating that some cultivars may be suitable for year-round production while others have seasons when production is optimized.