Introduction. Material and Methods

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1 STAKE, RACK, AND GROUND CULTURAL SYSTEMS INFLUENCE FRESH MARKET TOMATO YIELD, FRUIT QUALITY, AND POSTHARVEST ATTRIBUTES P. J. Nitzsche and W. H. Tietjen Rutgers Cooperative Extension of Morris County P.O. Box 900, Morristown, NJ , U.S.A. Abstract: New Jersey fresh market tomato growers have adopted stake culture over ground culture to improve yields and fruit quality. Stake culture, however, requires large inputs of labor. Rack culture may offer a compromise for small scale growers, requiring minimal labor while still producing high yields of quality fruit. Field trials in 1995 and 1996 compared ground unpruned, ground pruned, stake pruned, and rack pruned cultural treatments. Marketable yield was reduced in all treatments which were pruned. Plants in the ground unpruned treatment produced fruit with the lowest average fruit weight. In 1995 fruit from the ground unpruned plants were characterized by an undesirable flattened shape. Fruit quality was excellent in all treatments and there was little postharvest fruit loss in any treatment after storage. Keywords: tomato, staking, rack, pruning, culture Introduction The number of New Jersey tomato growers utilizing stake culture over ground culture has grown rapidly over the past five years (S.A. Garrison personal communication). Stake culture is utilized to decrease disease incidence, improve spray coverage, for ease of harvest, increased fruit size, to improve fruit quality, and postharvest attributes (Maletta et al,.1995; Scott, 1993; Tietjen et al.,1995). Stake culture, however, has higher costs of production than ground culture due to higher levels of labor and management (Scott, 1993). Rack culture is a system practiced by some small scale growers in Northern New Jersey. Wooden racks are utilized to support tomato plants and keep them upright. Rack culture has not been studied, however, it may offer growers a compromise between the two cultural systems. Rack culture should require less labor and management and may produce the quality and postharvest attributes of fruit grown under stake culture. The objectives of this experiment were to compare the influence of ground, stake, and rack cultural systems on fresh market tomato yields, fruit quality, size, and postharvest attributes and to examine the influence of pruning on fruit size, and shape of fresh market tomatoes grown under ground culture. Material and Methods Field studies in 1995 and 1996 were conducted on Quakertown silt loam (fine-loamy, mixed mesic, Typic Hapludults) in Pittstown, N.J. Limestone, P, K, based on soil test results (Garrison, 1995), and 501bs N/A, were broadcast-applied and incorporated. 'Mountain Spring' tomatoes were seeded April 24, 1995 and April 29, 1996 and transplanted into the field June 1, 1995 and June 4, Plants 247

2 were spaced 18" apart on raised beds spaced six feet apart and covered with black plastic mulch. All beds were supplied with trickle irrigation. In bs/A N, P, K was applied one week after transplanting and lolbs/a N, P, K applied eight weeks after transplanting through the irrigation system. In 1996, 2001bs/A N, P, K was applied one week after transplanting and 51bs/A N, P, K applied five weeks after transplanting through the irrigation system. Chlorothalonil (Tetrachloroisophthalonitrile) at 1.92oz/A was applied to control fungal diseases on a schedule determined by the TOM-CAST disease forecasting system with DSV accumulations (Pitblado, 1992). Recommended weed, and insect controls were applied as needed (Garrison, 1995). The four cultural treatments consisted of the following: ground culture unpruned, ground culture pruned to the "fork" (all lateral shoots removed from the base of the plant up to, but not including the shoot immediately below the first flower cluster on the main stem), stake culture pruned to the "fork," and rack culture pruned to the "fork." Plants in the rack culture treatment were trained to grow through A-frame racks constructed of 1"X 2" lumber as illustrated in Figure 1. Plots consisted of 10 plants and each plot was replicated four times in a randomized complete block design. Fruit exhibiting any pink color were harvested weekly from the middle eight plants in a plot. The marketable fruit was graded into four size categories (small <2.5", medium ", large 3-3.5", and extra large > 3.5") and weighed. Culls were examined and weighed separately. Samples of marketable fruit (10 medium fruit / plot) were removed from the August 23, 1995, and August 28, 1996 harvests and measured to determine diameter and height. These values were then divided to calculate a fruit height / diameter ratio. Marketable fruit samples were also removed at these harvest dates and placed in storage at 60 degrees F for one week, and then examined to determine postharvest losses. 248

3 Results and Discussion Marketable yield was reduced in all cultural treatment plots which were pruned (Table 1.). This reduction is consistent with past studies which have shown that pruning can reduce the total yield of tomato plants (Olson, 1996; Davis, 1993). Tomato yield has also been shown to vary according the level of pruning practiced (Olson, 1996). The large yield reduction in this study may indicate that this cultivar should be pruned less severely to achieve higher yields. Plants in the pruned treatments yielded less cull fruit. The cull yield consisted of fruit misshapen from being wedged deep in the crop canopy, and very small fruit < 2.0" in diameter. There were very few fruit culled due to ground rots in 1995 an extremely dry growing season, or in 1996 a cold wet growing season. The stake, rack and ground cultural treatments had no significant effect on marketable or cull yield from pruned plants. Karlen and Robbins (1983) also found that staking alone did not significantly affect tomato yield. In another study, however, Maletta et al. (1995) found that staking significantly increased marketable yield due to a reduction in foliar disease incidence. There was little to no foliar disease found in any of the cultural treatments in this study. Yield differences due to the cultural treatments might only appear when disease pressure is heavier. Pruning significantly influenced average fruit weight (Table 2.). In both years, plants in the pruned treatments produced significantly heavier fruits than those in the unpruned ground treatment. Many researchers have found that the removal of axillary shoots increases tomato fruit size (Aung and Kelly, 1976; Leopold and Lam, 1960; and Davis and Estes,1993). In 1996 plants grown in the stake treatment had the greatest average fruit weight. Fruit shape was influenced significantly in 1995 only. Fruits from the ground unpruned treatment were more flattened, less globular in shape as indicated by height/diameter measurements. It is unclear whether this shape change was a cultivar response to pruning, specific weather conditions, or some other factor. Fruit size distribution was influenced by the cultural treatments (Table 3.). Plants in the ground unpruned treatment produced the most fruit in the medium category while plants in the ground pruned, stake, and rack cultural treatments produced more fruit in the large and extra large categories. Davis and Estes (1993), showed pruning caused similar shifts toward larger fruit size categories in their study. In both years there was little to no postharvest loss in any of the treatments after one week in storage (data not shown). Tietjen et al. (1995) found that staking only influenced postharvest decay in a wet year. The lack of postharvest decay in this study may have been due to the excellent air drainage, pest control practices, and weather conditions at the field location. Postharvest losses are likely to increase under commercial growing and handling conditions and may be more heavily influenced by the different cultural systems. Further studies are needed to determine the influence of these cultural systems under less than optimal disease control situations. 249

4 Table 1. Marketable and cull yield of tomatos as influenced by cultural system. Marketable Cull Yield Yield Cultural System (lbs/acre) (lbs/acre) 1995 Ground, Unpruned 64,390 a z 14,641 a Ground, Pruned 43,675 b 12,475 ab Stake, Pruned 49,229 b 9,837 b Rack, Pruned 45,460 b 9,541 b 1996 Ground, Unpruned 69,157 a 17,267 a Ground, Pruned 49,755 b 12,741 b Stake, Pruned 48,860 b 12,033 b Rack, Pruned 49,356 b 11,332 b z Mean separation in rows by Duncan's Multiple Range Test (P=0.05) Table 2. Fruit size and shape as influenced by cultural system. Cultural System Average Marketable Fruit wt (oz) Height/Diameter Ratio 1995 Ground, Unpruned 6.9 b z b Ground, Pruned 9.4 a a Stake, Pruned 9.4 a a Rack, Pruned 9.8 a a 1996 Ground, Unpruned 9.28 c a Ground, Pruned b a Stake, Pruned a a Rack, Pruned b a z Mean separation in rows by Duncan's Multiple Range Test (P=0.05) 250

5 Table 3. Tomato fruit size distribution as influenced by cultural system. Marketable fruit size distribution (% of marketable yield by weight) Small Medium Large Extra Large Cultural System <2.5" " 3-3.5" >3.5" 1995 Ground, Unpruned 0.0 a z 26 a 68 be 6.0 b Ground, Primed 0.6 a 17b 62 c 20 a Stake, Pruned 0.3 a 7.2 c 77 a 15a Rack, Pruned 0.5 a 9.0 c 72 ab 18a 1996 Ground, Unpruned a 81 a 10c Ground, Pruned b 80 a 17 be Stake, Pruned be 71 b 28 a Rack, Pruned c 78 a 19b z Mean separation in rows by Duncan's Multiple Range Test (P=0.05) Conclusions Marketable yield, fruit weight, fruit shape, and fruit size distribution can all be manipulated by pruning practices. If markets demand larger fruit size, pruning should be utilized and the degree of pruning matched to the growth habit of the cultivar. If high marketable yields are desired, plants can be left unpruned on the ground under low foliar disease pressure. Stake and rack cultural systems should be considered if less than optimal conditions exist for fungal disease control and according to the availability of labor and management. Literature Cited Aung, L.H. and W.C. Kelly Influence of defoliation on vegetative, floral and fruit development in tomatoes (Lycopersicon esculentum Mill.). Proc. Amer. Soc. Hort. Sci. 89: Davis, J.M. and E. A. Estes Spacing and pruning affect growth, yield and economic returns of staked fresh-market tomatoes. J. Amer. Soc. Hort. Sci. 118(6): Garrison, S.A Commercial vegetable production recommendations. NJ Exp. Station Bulletin E001M. 164 pp. 251

6 Karlen, D.L. and M.L. Robbins Management practices for fresh-market tomato production in the southeastern coastal plain. HortSci. 18(5): Leopold, A.C. and S.L. Lam A leaf factor influencing tomato earliness. Proc. Amer. Soc. Hort. Sci. 76: Maletta, M.H., W.P.Cowgill, Jr., W.H. Tietjen, P.J. Nitzsche, and S.A. Johnston Comparison of disease forecasting for early blight control on stake culture versus ground culture fresh-market tomatoes in New Jersey. HortSci. 30(4)882. Olson, S.M Interaction of in-row spacing and degree of pruning on yield of 'Agriset 761' tomato. HortSci. 31(4)572. Pitblado, R.E TOM-CAST, a weather-timed fungicide spray program for field tomatoes. Mnistry of Agriculture and Food-Ontario. 18 pp. Scott, W.D It pay to stake and cage. Amer. Veg. Grower. August p Tietjen, W.H., M. Maletta, W.P. Cowgill, Jr., P.J. Nitzsche, and S.A. Johnston The efect of staking vs. Ground culture on tomato postharvest losses. HortSci. 30(4)