Transplant trays – does cell size matter?

Vegetable transplant producers have trended toward transplant trays with smaller cells to lower production costs, but is there a hidden cost that will only show up later? How might cell size affect yield, the real bottom line?

While production costs continue to increase, vegetable producers have little control over raising the price of their product to recover these increases. Therefore, growers are left with finding ways to continue lowering production costs wherever they can. One way to lower costs for transplanted crops is to use transplant trays with higher cell count. However, higher cell count means lower media and root volume. How might this influence total yield and financial returns?

To help answer this question for peppers, a trial was designed in 2013 by Michigan State University Extension personnel at the Southwest Michigan Research and Extension Center (SWMREC) in Benton Harbor, Mich. ‘Aristotle’ pepper seed was planted into trays having 72, 98, 128 and 200 cells in a 10.5-inch by 21-inch tray. Seed was planted April 1 in the greenhouse and plants set to the field May 22. Plants were raised using commercial practices and harvested three times. Plants were also destructively harvested on four dates and the above-ground portion weighed.

Data indicated early differences in plant weight (Table 1), but by first fruit harvest on Aug. 14, no differences were noted. There were few differences in fruit yield and quality and no differences in total yield and average number one fruit weight (Table 2). These findings are in agreement with other research trials on transplant cell size.

Table 1. Above ground weight in grams of four ‘Aristotle’ pepper plants from four transplant tray cell sizes at four dates in 2013. Plants were grown at SWMREC.

Cells/Tray

Weigh date

5/22

7/9

7/30

8/14

72

4.9

474

2,638.5

4,143.8

98

3.2

654.8

2,582.5

4,499.0

126

3.0

444.3

1,952.5

4,643.3

200

1.9

349.3

1,977.5

4,932.5

lsd .05

0.7

140.2

591.6

ns

Results from this and other trials for peppers and other transplants, including tomatoes, broccoli, cabbage and watermelon, found little differences in total yield, but did find differences in early fruit yield, especially pepper. This indicates producers wanting to save money by growing transplants in smaller-celled trays should not use small cell sizes for those plantings planned for early harvest, but they could use small cell sizes for mid- and late-season plantings.

Care must be taken when using smaller cell sizes since they require greater attention to watering in the greenhouse and especially after removal from the greenhouse and prior to planting. Smaller plant size at transplanting may also require increased attention to fertilizer rates and application between transplanting and first fruit set to be sure plants develop adequate size before plant growth slows.

Table 2. Yield in bushels per acre and size grades of ‘Aristotle’ bell peppers grown at SWMRECin 2013. Plant population was approximately 10,560 plants per acre.

Treatment
(cells/tray)

Total yield

Yield No.1

Avg. No.1 Wt. (gms)

Yield jumbo

Yield extra large

Yield large

Yield medium

Yield No.2

Yield cull

72

1191

928

195

177

265

323

164

79

184

98

1217

931

189

162

244

338

187

100

187

128

1164

911

193

146

221

371

173

58

195

200

1271

1032

203

247

299

321

164

54

185

lsd .05

ns

ns

ns

76

ns

ns

ns

35

ns

 For more information on commercial vegetable production, contact Ron Goldy at 269-944-1477 ext. 207 or .(JavaScript must be enabled to view this email address).

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