Study Application Effect of Impermeable Soil Layer and Date Palm Leaf Mulch on Some MorphoPhysiological and Biochemical Traits of Eggplant (Solanum melongena L.) under Low Irrigation Stress

 The use of natural and artificial mulches to reduce evaporation from the soil surface and retain moisture is one of the best measures to make optimal use of limited water resources and increase crop yields. Optimal production of plants in sandy soils has been challenged due to their low capacity in water retention and also production of plants in arid and semi-arid regions due to water shortage and drought stress. Water scarcity is increasing as a result of global warming, and attention is being paid to the methods that lead to water storage. Therefore, it is necessary to increase water consumption efficiency with new technologies. One of the new methods of water retention in the root zone is the use of a water retaining layer below the soil surface. By preserving water and elements in the root zone and creating a stable environmental state, it increases local production and economy by reducing soil erosion and groundwater pollution. Also, due to limited water resources, it is necessary to seek solutions to conserve water and increase water use efficiency. Mulch is considered as one of the best ways to retain water in the soil and reduce soil evaporation. Therefore, in this study, the application of impermeable soil layer on morphophysiological and biochemical traits of eggplant (Solanum melongena L.) was investigated using date leaf mulch under deficit irrigation stress.

 This study was conducted in Roudan, Hormozgan, Iran. Main plot includes deficit irrigation stress in three levels (100, 70,40 % of plant water requirement), sub-plot includes mulch in two levels (date leaves and no mulch) and sub-sub-plot includes impermeable layer in three levels (0, 100, 120 cm). Eggplant seeds of the local variety Rudan were planted in the seedling tray and transplanted when the seedlings were about 15 cm long or 5-6 leaf stage. Shortly after transplanting the seedlings to the field, daily irrigation was performed. CROPWAT software was used to calculate 100 % of the water requirement. Stress was applied using drippers with lower flow rate or reduced irrigation hours and by installing water meters.

 The results showed that the highest plant height (78 cm) belonged to date palm mulch, layer impermeable at depth of 120 cm and 100% water requirement. The use of date palm mulch and impermeable layer, especially the impermeable layer, has led to an increase in the number of leaves and fruits in the eggplant. The highest number of leaves (189) belonged to the treatment without mulch and with an impermeable layer of 120 cm soil depth in 100 % water requirement and the lowest (75.13) belonged to the treatment without mulch and impermeable layer in 40 % water requirement. The highest number of fruits belonged to the treatment without mulch and impermeable layer at depth of 120 cm and 100 % water requirement and the highest amount of dry matter (12.5%) belonged to the treatment of date palm mulch and impermeable layer at depth of 120 cm and 100 % water requirement and the lowest (1/9%) belonged to date palm mulch without impermeable layer and 70% water requirement. The results showed deficit irrigation stress reduced the amount of chlorophyll a, b and total in eggplant. The use of date palm mulch and impermeable layer in water requirement of 70 and 40 % has increased the amount of chlorophyll, which seems to be used in case of water shortage, reduce the adverse effects of dehydration and prevent the destruction of chlorophyll in eggplant. The highest amount of total chlorophyll belonged to the 100 % water requirement, without the use of date palm mulch and impermeable at depth of layer 120 cm. The highest amount of proline in this study belonged to treatment without date palm mulch, application of impermeable layer at depth of 0 cm and water requirement of 40 % and the lowest belonged to the treatment of date palm mulch, application of impermeable layer at depth of 120 cm and 100 % water requirement. The highest amount of eggplant water use efficiency was obtained in 40 % water requirement, use of date palm mulch and impermeable layer at depth of 120 cm. The results of this study also showed that deficit irrigation stress reduced fruit yield in eggplant and the use of date palm mulch and impermeable layer also increased eggplant yield. This increase in fruit yield is especially noticeable in the use of date palm mulch and impermeable layer at depth of 120 cm.

 It seems that the impermeable layer and date palm mulch have reduced the negative effects of water stress on the plant, increased fruit yield and water use efficiency and reduced the effects of stress.