Date-Palm Compost as Soilless Substrate Improves Plant Growth, Photosynthesis, Yield and Phytochemical Quality of Greenhouse Melon (Cucumis melo L.)

Abstract

The selection of adequate substrate for soilless culture is based on technical and economic considerations. Therefore, the search for alternatives by the valorization of natural by-products is gaining importance. The main objective of this study was to compare the effects of local farm resources, date-palm waste, as culture substrate, to coconut fiber (CF) (commonly used in soilless culture) on melon (Cucumis melo L.) plant growth, water relations, photosynthesis, chlorophyll fluorescence as well as phytochemical analysis under hydroponics culture system. Two growing substrates were tested: the compost of date palm waste added to animal manure (7:3 w w−1) (DPAM) and the date palm trunk compost (DPT). Coconut fiber and soil were used as positive and negative controls, respectively, in randomized blocks. Results showed that the vegetative growth was improved under DPT and CF substrates while CF substrate enhanced fruit yield and phytochemical properties: Total soluble solids TSS (% Brix), total dissolved solutes (TDS); Titratable acidity (as citric acid); Sugar content and juice pH of melon fruit. Date-palm waste-based substrates enhanced the vegetative growth and the fruit yield of melon as compared to soil-based culture. It seems that date palm waste-based substrates, especially trunk compost, could be promising and cheaper alternatives compared to coconut fiber substrates commonly used in Tunisia in soilless cultures.

Optimizing Alternative Substrate for Tomato Production in Arid Zone: Lesson from Growth, Water Relations, Chlorophyll Fluorescence, and Photosynthesis

“…Thus, we can deduce that organic substrates have a positive effect on the RWC compared to the soil substrate. Our results are similar to recent studies which have indicated the positive effect of compost on maize and melon water status by increasing foliar RWC [ 24 , 25 ]. Indeed, the high leaf water content reflects the better photosynthesis of the plant, as well as good cellular functioning [ 26 ].…”

“…This was associated with an increasing antioxidant activity ( Figure 4 ). These results confirm the higher nutritional quality of fruits grown on organic substrates [ 25 , 46 ]. The highest values of antioxidant activity were detected in DPAM fruits.…”

“…Titratable acidity values in this study (0.9–1.2%) were high compared to those reported by Al-Kahtani et al [ 43 ] in the variety “Asala F1” (0.30–0.56%). The positive effect of organic substrate on sugar content has previously been reported in blueberry, strawberry, and melon [ 25 , 44 , 45 ].…”

“…The LΨs varied among substrates, the lowest in DPAM, then the DPT substrate, and the highest in the soil substrate ( Figure 1 E). The high LΨw and low LΨs associated with date-palm compost can be explained by the high field capacity and porosity and the water availability for plants from these substrates [ 25 ]. Fascella et al [ 27 ] showed that the positive effect of the substrate on plants grown in soilless greenhouse conditions was related to the improvement of water retention.…”

“…This value was only 8.72 mg g −1 DW in soil ( Figure 2 ). The influence of substrate type on total chlorophyll content has previously been studied, showing the positive effect of the date-palm waste substrate on the total chlorophyll content of cucumber and melon compared to the soil substrate [ 16 , 25 ]. Additionally, Ghouili et al [ 30 ] revealed the influence of plant waste compost (date palm) and manure on the increase in total chlorophyll content in tomato leaves.…”