Melon Row Covers

by Henry G. Taber and Vince Lawson

Department of Horticulture, Iowa State University

Updated: December, 1997

Melon Row Covers

Melon Plastic Mulch

The use of plastic mulch on muskmelon is a proven profitable practice in central Iowa. We consistently increase early yields (see Table 1).

Table 1. Effect of plastic mulch on yield of muskmelons, cv. Burpee hybrid, Ames, Iowa, 1978 to 1982.

Treatment	1978	1979	1980	1982	1991	1992	Average
	Early yield, cwt/acre
Bare soil	42	62	84	32	40	50	52
Black plastic	55	173	--	148	78	113	113
Clear plastic	167	227	383	155	118	175	204
	Total yield, cwt/acre
Bare soil	217	434	441	188	399	237	319
Blackplastic	293	478	---	250	475	351	369
Clear plastic	269	535	592	273	427	334	405
NOTE:	Transplants were set early part of May and early harvest was late July to early August. Total yield to first week of September. Soil type = fine, sandy loam; well drained.

Note that for early yield clear plastic outperforms black plastic in all years, +81%; and +292% over bare ground. The main cause is the increase in soil minimum temperature. The vine crops are much more responsive to elevated soil temperatures than tomatoes and peppers. The soil was a well-drained sandy loam. The earliest that the first harvest occurred was July 24, 1980. Of course, one would have to use an herbicide under the clear plastic to prevent weed growth. On heavier soils, such as loams, the plastic not only greatly increases the first ten day yield, but it advances maturity by three or four days. An example was the 1988 growing season on a loam soil. Transplants were set May 12 in bare ground or clear plastic mulch. Harvest began on July 22 from clear plastic and August 1, from bare ground plots.

Weed control with clear plastic is important. Obtain a copy of FG-600, titled "Midwest Vegetable Production Guide for Commercial Growers," from your local county extension office or Ag Publication Distribution, 112 Printing and Publications Building, Ames, Iowa 50011, for recommended herbicides. The new IRT mulches perform equivalent to clear plastic and are worthy of trial. They are green in color and allow light radiation of long wavelengths through to warm the soil, but block light wavelengths needed for plant growth. Thus, an herbicide would be needed with IRT mulch and the row middles could be kept weed free by mechanical means.

For the spring of 1990, a cool, wet spring, the average 4-inch bare soil minimum temperature was 52 degrees F from May 15 to 31 (Table 2). The 4-inch minimum soil temperature under clear plastic was 57 degrees F and the IRT 76 plastic 58 degrees F. Similar results were found in 1992. The major weed species were redroot pigweed, purslane, chickweed, lambsquarter, foxtail, crabgrass, and smartweed. For the most part, IRT 76 plastic was weed free. However, where there was a heavy chickweed infestation and some did grow under the IRT 76 mulch. See row cover section below for yeild information with IRT 76 compared with clear plastic.

Table 2. Soil temperatures, degrees F, under various mulch types with muskmelon, cv. Gold Star, Ames, Iowa, 1990 and 1992.

Material	Minimum degrees F		Plant Survival, %
	1990	1992	1990	1992
Bare ground	52c1)	55c	7b	64c
Black plastic	55b	57b	22a	86a
Clear plastic	57a	59a	59a	93a
IRT 76 plastic	58a	58a	67a	79b
1)Numbers followed by the same letter within a column are not significantly different, DMRT, 5% level. Thermocouples (3/treatment) were placed to the side of the transplant (about 3 inches) just under the plastic.

On the coarse, sandy soils along the Mississippi River at Muscatine, Iowa, the plastic effect is similar on early yield as in central Iowa (see Table 3).

Table 3. Effect of black plastic mulch on yield of muskmelons, cv. Burbee hybrid or Gold Star, Muscatine, Iowa, 1978-1983.

Year	Early, cwt/acre		Total, cwt/acre
	Bare Soil	Black Plastic	Bare Soil	Black Plastic
1978	29	72	156	177
1979	94	124	204	208
1982	40	190	184	247
1983	32	54	163	193
Average	77	110	177	209
NOTE:	Transplants were set mid-May and early harvest from July 23 to August 1, total yield to mid-August. Soil type = coarse, loamy sand; excessive drainage.

The black plastic mulch doubled early yield production. At this location there is a more dramatic effect on total yield than is found in central Iowa. This is probably related to two reasons: 1) a more even moisture supply during the crowing season than possible with bare soil even though irrigated, particularly during the heavy fruiting period; 2) the prevention of nitrogen leaching on these coarse, sandy soils. However, these soils warm up quickly in the spring and plastic does not advance maturity date, but the early yield in the first ten days i greatly increased. For the same reason, there is no advantage on these coarse, sandy soils of clear plastic over black plastic mulch (data not presented).

Melon Row Covers

On the two basic row cover types, wire-hoop supported and floating row covers, the floating row cover has not been successful under most central Iowa conditions because of wind (Table 4).

Table 4. Effect of floating row cover on early muskmelon, cv. Gold Star, yield, Ames, 1983-84. No windbreaks, sandy loam soil.

Plant Cover	No. / Plot	Cwt / Acre
	1984	1983
None	15	154
Clear, slitted	33	305
Reemay	9	160
NOTE: All treatments grown with clear plastic mulch and trickle irrigation.

Table 5. Effect of hoop supported, slitted, clear plastic row covers on muskmelon, cv. Gold Star, early yield, Ames, Iowa, 1982-1992.1)

Year	Plant Cover
	None	Clear, slitted
1984 (No./plot)2)	15	33
	Cwt / Acre
1982	71	191
1983	154	305
1985	90	185
1987	68	138
1991	118	238
1992	175	390
6-year average	113	237
1)All treatments grown with clear plastic mulch and trickle irrigation. 2)Hailed out on June 26. All fruit harvested on July 5.

The constant abrasion of the material against the young transplants stunts growth, reducing early yield, very similar to the effect on tomatoes. The hoop-supported clear slitted plastic has always given an increase in early muskmelon production in central Iowa. Note the doubling of early yield in 1987 (Table 5) when May temperatures were the warmest on record (+5.5 degrees F above normal).

Clear plastic and IRT 76 tripled early yield compared with bare ground in 1991 and 1992 (Table 6). But top yields both years were from the combination of row cover with either clear plastic or IRT 76 mulch. Yield from clear plastic was superior to that from IRT 76 by 41 cwt/acre in 1991, but not in 1992. Crop rotation and herbicides were used to provide adequate weed control both years. Currently the extra cost of the IRT mulch does not justify its use unless weeds are a severe problem.

Table 6. Effect of plastic mulch type and slitted, hooped, clear plastic row covers on early and total marketable muskmelon, cv. Gold Star, early yield, Ames, Iowa, 1991-1992.

Mulch Treatment	Early Marketable Yield1), cwt/acre
	1991	1992
None	40	50
Clear Plastic (CP)	118	175
CP + Sl. Row Cover	213	390
IRT 76 (IRT)	100	128
IRT 76 + Sl. Row Cover	149	367
Comparison2)
None vs Rest	*	**
RC vs No RC	**	**
CP vs IRT	*	NS
1)Early yields harvested during the first 10 days. 2)Contrasts calculated by partitioning the treatment effects using SAS general linear models procedure; *, **, NS contrasts significant, respectively.

Where there is ample wind protection, a floating row cover will perform as well as a hoop-supported slitted clear plastic. Table 7 shows three years of data on the coarse, sandy soils on the Muscatine Island. Approximately 20-inch rye strips were left between each row. Under these conditions, the floating Reemay row cover performed as well as the hoop-supported slitted clear plastic.

Table 7. Effect of row covers on early muskmelon, cv. Gold Star, yield, Muscatine, 1985-1987. Windbreak every row; coarse, loamy sand soil.

Plant Cover	Yield, cwt/acre -- 3-year average
	Early	Total	Fruit Size
None	57	218	4.1
Clear, slitted	82	217	4.2
Reemay	85	190	4.0

Combining clear plastic mulch and a row cover for early muskmelon production has great advantages. A basic disadvantage is that trickle irrigation must be used with this system on the coarse, sandy soils. Overhead irrigation does not penetrate the cover and reach the small root systems of the developing plants. This results in delayed maturity and sometimes even death.

............Justice for All

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Cooperative Extension Service, Iowa State University of Science and Technology and the United States Department of Agriculture cooperating. Stanley R. Johnson, director, Ames, Iowa. Distributed in futherance of the Acts of Congress of May 8 and June 30, 1914.