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Use of Plasticulture for the Production of Melons

Posted: March 9, 2011

Since Cucurbits in general and melons specifically love warm temperatures, production of melons (cantaloupe and watermelons) in much of Pennsylvania is a challenge both from the standpoint of temperature and moisture. Melon plants stop growing below 45°F and will have a difficult time maturing fruit when average night temperature drops below 50°F. Optimum growth of melon plants is between 75° and 85°F daytime temperature.

For the average grower in Pennsylvania growing on bare soil, the planting date for melons is generally between May 20 and June 15, assuming that there will not be extremes in day and night temperatures. While mature cantaloupe and watermelon plants are somewhat drought tolerant, they require consistent soil moisture levels (80% of available soil moisture) after seeding or transplanting and until they reach the 10-12 leaf stage of growth. On the other hand, excess rainfall 2 weeks prior to fruit harvest will dramatically reduce soluble sugars and fruit quality. The use of plasticulture will help eliminate/prevent these environmental stresses on melon plants during the growing season.

If seeding melons in the field, minimum soil temperature 2” to 3” below the soil surface must be at least 60°F. Also, if conditions are cool and wet, scout the field for potential seed corn maggot infestation. Air temperature after seeding should be minimum of 50°F as a night time low and air temperatures below 45°F will have a negative effect on seed germination, emergence and early seedling growth. If transplanting, use a 26 to 32 day old seedling with no visible flowers. Transplant melons into plastic covered raised beds when soil temperature 2” to 3” below the soil surface is at least 55°F.

For the production of high quality melons, the use of raised beds, plastic mulch (black or blue), drip irrigation and row covers will ensure success and consistent marketable yields. The use of plasticulture in the production of melons will:

  • increase soil temperature 8° to 12°F warmer than bare soil,
  • increase/maintain soil water holding capacity,
  • reduce/eliminate weeds,
  • maintain/increase soil tilth and
  • reduce/eliminate fertilizer and pesticide leaching under the bed.

I will discuss the individual components of plasticulture in the following sections below.

Raised Beds

Making a 6 to 8 inch raised bed prior to applying plastic mulch in the field helps to;

  • increase soil temperature,
  • produce a tight fit of plastic on the soil surface,
  • prevent plant/fruit damage from excessive water (heavy thundershowers),
  • reduce soil erosion when beds follow soil contour and
  • helps to produce a higher quality, cleaner fruit.

Many equipment manufacturers sell a multi-function machine which will make a raised, pressed bed, lay the agricultural film snugly on top of the bed and also place drip tape at a desired depth in the bed at one pass. In addition, a fertilizer applicator can be placed on top of the bed maker/mulch applicator to add nutrients into the bed.

Plastic Mulch

Since plastic mulch increases soil temperature, soil moisture and maintains soil tilth, seeding or transplanting melons within 2 to 5 days after application of the plastic in the field is recommended. Plastic film can be purchased at a thickness of 0.3 to 1.5 mil, embossed or smooth and in colors of clear, white, black, blue, IRT green, IRT brown, red, yellow and silver. The plastic film you purchase can be tailored to your needs based on crop being grown, number of crops to be grown on the film, length of time to be left in the field and pest elimination requirements. The thicker the film, the longer it can be left in the field; 1.5 mil plastic will last two years/multiple crops in the field. However, in general, the thicker the film, the higher the cost; unless the purchase is an ultra-thin plastic film 0.3 mil or less. Embossing imparts more elasticity/stretchability compared to the smooth plastic film. As to color, melon plants will produce higher early and marketable yields on IRT green, blue or silver compared to the standard black. The silver mulch also repels aphids so that aphid vectored viruses are eliminated in the field. Melons also perform very well on biodegradable plastic mulch.

Drip Irrigation

Water comprises 94% of melon fruit which would verify the importance of water in the growth and development of melon plants and fruit. Whether seeding or transplanting melons, application of water is extremely important to maintain soil capacity for germination of melon seeds or the regeneration of root and shoot growth of melon transplants. Drip irrigation is very efficient in directing water to the crop and not the weeds, reducing/eliminating foliar diseases, and injection of fertilizers and/or pesticides. Since many soils in Pennsylvania are silt loams to clay loams and generally have between 1.5% to 2.5% organic matter, they tend to have relatively high cation exchange capacity (CEC), low to moderate water infiltration rates, and moderate to high water holding capacity. Because of these characteristics, growing melons on these soils and raised beds/plastic mulch is more effective when at least 40% of the fertilizer requirement is added preplant rather than totally through the drip irrigation system. Fertigation of nitrogen (approx. 7 to 10 lbs/A) after crown set fruit are harvested does help to increase fruit production and maintain plant health and vigor. Scheduling water application on measurement of actual soil moisture levels (irrometer or tensiometer or ET values) will help to maintain active plant growth throughout the growing season and produce high sugar, high quality fruit. Remember that soluble solids or sugars are translocated to the fruit within the last two weeks prior to the fruit becoming full slip. Application/reception of excessive moisture during this period of carbohydrate movement from plant to fruit will dramatically reduce the sugar level and overall quality of the fruit.

Floating Row Covers

Since melon crops return a relatively high gross per acre and require warm temperatures both day and night, use of polypropylene row covers is both economical and productive. Applying row covers on the raised bed/plastic mulch after seeding or transplanting melons will increase both ambient and soil temperature resulting in increased plant growth, reduce/eliminate plant desiccation, maintain higher soil moisture levels, and exclude insect feeding on young plants. However, once female flowers are observed on plants, the row cover must be removed to allow for pollination by honeybees. While polyester row covers are available, the stiffness of the material compared to polypropylene will cause leaf abrasion and potential delays in fruit maturity.

Low Tunnels

In locations that are rather windy in the spring of the year and plant desiccation is a principle cause of plant mortality, use of low tunnels will help both establishment and early production of melons. Low tunnels are usually 1-mil rolls of perforated (for ventilation) polyethylene stretched over metal hoops (no. 9 wire) placed every 6’ to 8’ over the row of melon plants. The tunnels are immediately placed over the row after transplanting and left in place until the afternoon high temperatures exceeds 85°F for 3 successive days.

Tips for Successful Melon Production with Plasticulture:

  • Use raised beds (4 to 6’’ high) when laying plastic in the field compared to flat beds to insure better water and nutrient management in the field.
  • Prior to making raised beds in field, broadcast and incorporate 40% of total nitrogen requirement for melon crop and all the phosphorus and potassium recommended by soil test.
  • When laying plastic in the field, make sure soil is at least 85% of water-holding capacity.
  • Wait at least 2 to 3 days after laying plastic mulch in the field before transplanting or seeding melons through the plastic.
  • After seeding and especially after transplanting melon plants through plastic mulch, monitor soil moisture level underneath the plastic mulch and maintain moisture level by use of drip irrigation system.
  • Monitor melon plants for both cucumber beetle and aphid populations since both insect species can rapidly reproduce and vector viral or bacterial organisms to young melon transplants.
  • Remove row cover or mulch from low tunnel when first female flowers appear in field.
  • Place at least one active beehive per acre of production to insure pollination and fruit production.
  • Fertigate with low levels of nitrogen (5 to 7 lbs/A) throughout the growing season.
  • Apply one pound per acre Boron pre-bloom stage either through the drip irrigation system or as a tank-mix with fungicide spray.
  • Reduce water application to melon crop within 2 weeks of the bulk harvest of melons in the field to improve soluble solid levels and higher fruit quality.