The development of melon roots under trickle irrigation: Effects of the location of the emitters

Abstract

Desert agriculture is highly dependent upon trickle irrigation. Usually, plant roots that develop under high frequency trickle irrigation are shallow and densely crowded. As a result of that, plants become sensitive to temporal fluctuations in water availability, in temperature and in salinity. Thus, an attempt was made to establish a root system that will minimize the above mentioned hazards.

Winter melons (Cucumis melo cv. Haon), were grown under four irrigation treatments with tricklers placed at four different depths: surface, 15 cm, 30 cm and 45 cm. Root development was measured at harvest time, using the “wall profile” method. Distribution of the roots at various soil horizons, depended upon the depth of the emitters. Most roots have developed at the depth of 15–20 cm, in surface irrigation, and in the 15 cm deep treatments. Highest root densities were obtained at the depth of 25–30 cm, in the 30 cm deep emitters treatment, and at 35–40 cm where the emitters were 45 cm deep. Distribution of salt across the soil profile also depended upon the depth of the emitters; concentration of chloride at the soil surface was approximately 30–50 mM, in treatments with shallow emitters but reached a concentration of 1447 mM in the 45 cm treatment. Daily fluctuations in temperature were highest at the soil surface and negligible at the depth of 40 cm. As low root temperatures have an adverse effect on the water uptake capability of winter crops, plants with deeper roots should have an advantage. Indeed, melon plants of the 45 cm treatment remained green and vital throughout the winter, whereas plants with shallow roots developed scorched leaves and were severely damaged.

Thus, it seems possible to manipulate the architecture of the root systems of melon plants by regulating the depth of the emitters of the trickle irrigation system.