Comparison of Organic and Inorganic Mulches for Heirloom Tomato Production

 

Elaine M. Grassbaugh, Emilie E. Regnier, Mark A. Bennett and Richard M. Riedel

The Ohio State University, Dept of Horticulture & Crop Science

                                         

Introduction

      Many tomato growers face challenges in producing their crops due to stricter environmental regulations and fewer chemicals available for weed control.  There is a demand for cultural practices that reduce chemical inputs and synthetic materials (Abdul-Baki et al., 1996).  Such production practices need to focus on controlling weeds, reducing soil erosion, and maintaining soil moisture and structure while producing high quality fruit and maintaining profitable yields.  Plastic mulches have been used in vegetable production to increase soil temperatures, reduce weed pressure and increase yields (Lamont, 1991).  However, disposal of this material can be costly, while adding nothing to the soil structure or fertility.  Use of cover crops and living mulches has produced mixed results.  Good cover crop or living mulch management requires a balance between effective weed control and competition with the crop being produced.  Organic mulches may be a feasible option for weed control and can be as effective as herbicides in suppressing weeds (Ozores-Hampton, 1998).  Heirloom varieties, once traditionally grown in backyard gardens, are becoming more popular among commercial tomato growers due to increased demand from consumers. These older varieties are mainly indeterminate in habit, open-pollinated and offer unusual colors, shapes and sizes.  Since most heirloom tomatoes at present are grown on small acreage, the addition of organic mulches may be a feasible practice for growers.

 

Objectives:

      To test organic and inorganic mulches along with a bare-ground control with and without pesticide inputs for an heirloom tomato cultivar ‘Nebraska Wedding’.  Treatments were evaluated for marketable yield, soil temperatures, weed density and biomass, disease ratings, and decomposition rate of organic mulches.

 

Methods and Materials:

The experiment was established at the OSU Waterman Agricultural and Natural Resources Laboratory, Columbus, Ohio on June 1, 2000.  Treatments consisted of 5 mulches (black plastic, shredded newspaper, wheat straw, composted landscape bark and bare ground control) and 2 pesticide input levels:  pre-emergence herbicides (Dual Magnum, Sencor, Treflan) plus fungicide applications (Bravo, Benlate, Quadris) as needed throughout the season or no pre-emergence herbicide or fungicide applications.  Treatments were arranged in a RCB design with 4 replications.  Drip irrigation tape was installed under mulch in all plots.  Rows were 7.6 m long and spaced 1.5 m apart.  Each row contained 5 plants spaced .91 m apart (Fig. 1).  Seven-week-old transplants were hand-planted into plots. Organic mulches were applied, by hand, to the tops of raised beds to a depth of 10 cm.  Soil temperatures were taken every morning at approximately 8 AM from soil thermometers inserted 5 cm into the soil under the mulches. Plants were staked and tied as needed using the Florida-weave method.  Plots were harvested weekly from August 22 to September 22.  Marketable and cull fruit number and weight were recorded.  Weed density and shoot biomass were collected on October 2 from two 0.5 m2 areas from each raised bed.  Weed counts and dry weights were recorded.  Organic mulch decomposition rate was calculated by placing nylon bags filled with 125 g of mulch in the field and collecting bags every three weeks for dry weight measurements.

 

Results and Discussion:

     Marketable yields for the 10 treatments ranged from 3.4 to 50 MT/ha (Table 1).  Highest marketable yields were achieved with shredded newspaper mulch, regardless of pesticide input.  There was no significant mulch x pesticide interaction for yield.  Bare ground control with no pesticide inputs resulted in the lowest yields.  Although newspaper produced the lowest soil temperatures, on average, shredded newspaper produced the highest yields of the organic mulches at low or high pesticide input.

There was a significant mulch x pesticide interaction for weed density and biomass.  Bare ground controls with no pesticide inputs resulted in the highest weed densities and biomass.  Weed densities and biomass were greater in the low vs. high pesticide input plots.  Predominant broadleaf weeds were pigweed (Amaranthus spp.), common lambsquarters (Chenopodium album L.), common purslane (Portulaca oleracea L.) and hairy galinsoga (Galinsoga ciliata (Raf. Blake).

Newspaper suppressed weeds more than any other organic mulch at both low and high pesticide input levels while producing the highest yields.  Newspaper had the lowest decomposition rate (Table 2) and may have formed a better barrier against weed emergence.  Although plastic mulch produced the highest soil temperatures, it produced the lowest yields compared to the organic mulch treatments for low and high input levels.  Previous research has shown that higher tomato yields are attributed, in part, to higher soil temperatures (Abdul-Baki et al., 1992; Ashworth and Harrison, 1983; Decouteau et al., 1989).

Disease ratings were taken on September 15, 2000. Predominant diseases present on foliage and fruit were early blight, septoria leaf spot, canker, rhizoctonia soil rot, and bacterial speck.  Plants in plots with wheat straw mulch had fewer septoria leaf spots compared to landscape bark.  Bare ground controls and shredded newspaper plots showed less early blight symptoms compared to plots with landscape bark mulch and wheat straw.  Early blight is known to be more severe in low N soils. 

In an attempt to reduce chemical inputs for tomato production, the effects of organic mulching materials, especially with reduced chemical inputs may be a viable option for small-acreage vegetable growers.

 


Fig. 1. 


 


Table 1.  Marketable yield and final weed density and biomass; WANRL, Columbus, OH. – 2000.

Mulch/pesticide input

Yield MT/ha

Broadleaf weed density (plants/m-2)

Broadleaf weed biomass (g/m-2)

Bare ground (low)

3.4

33.3

873.95

Bare ground (high)

24.6

8.3

70.18

Black plastic (low)

25.8

2

59.55

Black plastic (high)

45.2

0

0

Shredded newspaper (low)

41.5

2.8

174.74

Shredded newspaper (high)

50.0

2.3

5.12

Wheat straw (low)

30.6

8.5

452.86

Wheat straw (high)

47.6

4

39.78

Landscape bark (low)

31.1

9.3

312.12

Landscape bark (high)

49.3

0.8

7.08

 

 

 

 

 

 

 

 

LSD (0.05)

17.99

5.30

241.53

 

 

 

Table 2.  Decomposition rate of organic mulches at 3, 6, 9, and 12 weeks after placement in the field; WANRL, Columbus, OH- 2000.

 

   Dry weight loss of organic mulches (%).

Mulch

3 wks

6 wks

9 wks

12 wks

Shredded newspaper

0.6

1.12

1.60

3.6

Wheat straw

6.6

8.5

8.6

11.7

Landscape bark

4.8

9.0

11.1

11.1

 

 

 

 

 

 

 


 


References:

 

Abdul-Baki, A., C. Spence, and R. Hoover.  1992.  Black polyethylene mulch doubled yield of fresh-market field tomatoes.  HortScience 27(7):787-789.

 

Abdul-Baki, A., J.R. Teasdale, R. Korcak, D.J. Chitwood, and R.N. Huettel.  1996.  Fresh-market tomato production in a low-input alternative system using cover-crop mulch.  HortScience 31(1):65-69.

 

Ashworth, S. and H. Harrison.  1983.  Evaluation of mulches for use in the home garden. HortScience 18(2):180-182.

 

Decoteau, D.R., M.J. Kasperbauer, and P.G. Hunt.  1989.  Mulch surface color affects yield of fresh-market tomatoes.  J. Amer. Soc. Hort Sci.  114:216-219.

 

Lamont, W.J., Jr.  1991.  Does modern plastics technology have a place in organic vegetable farming systems research and farming enterprises?  HortTechnology 1(1):138.

 

Ozores-Hampton, M.  1998.  Compost as an alternative weed control method.  HortScience 33(6):938-940.

 

Acknowledgements:

 

Special thanks to:

USDA/SARE Competitive Grants Program and

Ohio Vegetable and Small Fruit Research and Development Program

for their financial support of this project.