Melon plants have an extremely widespread and deep root system which is highly efficient; this makes the plant structurally and functionally resistant to drought. However, this resistance can be substantially altered by growing conditions: mulching with plastic film, a prime example, results in a concentration of the greater part of the root system in the protected area of soil, and in the case of the melon, this leads to a reduction of approximately 50% in soil volume used. This reduction, however, is mostly offset by increased efficiency in the root system under the mulch, primarily due to the constant moisture levels and the higher temperature of the substratum.
Effects of irrigation
In the cultivation of melons with plastic mulch, increased production, both in open air and with semi-forcing, is obtained with sufficiently limited irrigation levels; irrigation which supplies the entire water needs of the plant have not resulted in increased production. Irrigation levels of between 50% and 75% of the plant’s water needs are recommended, however, special care must be taken during the flowering and filling phases of fruit development, when the crop is particularly sensitive to water stress.
The Irrigation System
In crops with plastic mulching, watering is normally by micro irrigation with drippers, iSiplastTape or driplines placed under the plastic film. This achieves two objectives:
- to convey water to the area occupied by almost the entire active root system
- to reduce to a minimum fluctuations in available water levels, thanks to the high frequency and low volumes of water needed by micro irrigation methods.
The best results are obtained by using driplines for maximum uniformity and precision in water distribution, especially when fertigation is required. Sprinkler irrigation on mulched crops is not recommended as it causes:
- the root system to develop near the surface and extend into the exposed inter-row space, where it can be crushed
- spread of pathogens
- leaching of nutrients
- prolonged contact of the fruit with the soil, which can cause rotting, deformation or discoloration in the area of contact.