Introduction
Water scarcity is considered one of the most serious environmental challenges limiting agricultural productivity worldwide. In semi-arid and drought-prone regions, insufficient water availability significantly reduces plant growth, crop performance, and overall yield stability. Countries with limited freshwater resources, such as Jordan, face major agricultural challenges due to low annual rainfall and prolonged dry seasons.
In Jordan, approximately 75% of agricultural land depends on rainfall, while only a small proportion is supported by partial or full irrigation systems. Rain-fed agricultural areas generally receive between 250 and 350 mm of annual precipitation, with rainfall concentrated mainly during the winter months. As a result, summer vegetable crops rely heavily on stored soil moisture during the growing season. Under these conditions, drought stress frequently limits crop development and reduces productivity.
Improving water use efficiency has therefore become a critical strategy for sustainable agriculture in semi-arid environments. One of the most effective methods for reducing water loss is minimizing soil surface evaporation. Agricultural mulching technologies, particularly polyethylene plastic mulch, have gained increasing attention for their ability to conserve soil moisture and improve crop performance.
Black polyethylene mulch is widely used in vegetable production systems under irrigated conditions because of its multiple agronomic benefits. However, its application under rain-fed farming systems remains limited despite its potential advantages in water-deficient environments. Summer vegetable crops such as squash (Cucurbita pepo) and okra (Abelmoschus esculentus) are commonly cultivated in semi-arid rural regions under rain-fed conditions, making them suitable candidates for mulch-based moisture conservation strategies.
Globally, the use of black polyethylene mulch has expanded due to its positive effects on soil and crop management. Research has shown that plastic mulch can:
- Increase soil temperature during early growth stages
- Reduce weed infestation
- Improve soil moisture retention
- Enhance nutrient use efficiency
- Promote earlier crop development
- Increase total crop yield
In water-limited agricultural systems, soil moisture conservation is essential for maintaining crop productivity. Black polyethylene mulch acts as a protective barrier that limits direct evaporation from the soil surface, helping preserve water within the root zone. In addition to moisture conservation, plastic mulch also suppresses weed growth, reducing competition for water and nutrients.
Although numerous studies have reported improved crop yields under polyethylene mulch compared with bare soil conditions, limited information is available regarding its effectiveness under rain-fed semi-arid environments. Therefore, evaluating mulch performance under these conditions is important for developing sustainable agricultural practices in drought-prone regions.
The objective of this study was to investigate the impact of black polyethylene plastic mulch on soil moisture conservation, vegetative growth, and yield performance of okra and squash cultivated under rain-fed conditions in a semi-arid environment.
Materials and Methods
Experimental Site
Field experiments were conducted during the summer growing season at the Al-Rabbah Agricultural Research Station, Faculty of Agriculture, Mutah University, Jordan. The region is characterized by a Mediterranean semi-arid climate with cold rainy winters and hot dry summers.
The area receives an average annual rainfall of approximately 350 mm, with most precipitation occurring between December and February. The experimental soil was classified as loamy sand with the following characteristics:
- Soil pH: 7.9
- Electrical conductivity: 1.59 dS m⁻¹
- Organic matter: 1.69%
- Calcium carbonate: 30%
- Total nitrogen: 0.061%
- Available phosphorus: 22 ppm
These soil and climatic conditions represent typical rain-fed agricultural environments in semi-arid regions.
Experimental Design and Treatments
The study was arranged using a Randomized Complete Block Design (RCBD) with three replications. Two soil management treatments were evaluated:
- Black polyethylene plastic mulch
- Non-mulched bare soil control
Each experimental plot consisted of six rows measuring 2.4 meters in length. Row spacing was maintained at 1 meter, while plant spacing within rows was 0.4 meters.
The experimental land was prepared through repeated plowing and harrowing operations before planting. Black polyethylene film with a width of 100 cm and thickness of 125 µm was installed over planting beds before sowing. The edges of the plastic film were secured using soil.
Seeds of squash cultivar Anita Hybrid and okra cultivar Clemson Spineless were sown during mid-April.
Soil Moisture Evaluation
Soil moisture content was measured at 30-day intervals throughout the growing season using the gravimetric method. Soil samples were collected from the upper 30 cm soil layer using manual coring techniques.
Measurements demonstrated that black polyethylene mulch significantly improved soil moisture retention compared with non-mulched soil. Mulched plots consistently maintained higher moisture levels throughout most stages of crop growth.
The mulch layer reduced direct evaporation from the soil surface, allowing more water to remain available within the root zone. This effect was particularly important during dry summer periods when rainfall was absent and crops depended entirely on stored soil moisture.
Effect of Mulch on Vegetative Growth
Seedling Emergence and Flowering
Black polyethylene mulch accelerated seedling emergence in both okra and squash crops. Germination occurred several days earlier in mulched plots compared with bare soil treatments.
The earlier emergence was likely associated with increased soil temperature and improved moisture availability beneath the mulch layer. Faster germination contributes to stronger early plant establishment and improved crop vigor.
Flowering time was also significantly advanced under mulched conditions. Plants grown with black plastic mulch reached flowering stages earlier than those grown in uncovered soil. Earlier flowering is an important agronomic advantage because it can extend harvest duration and improve market opportunities.
Plant Biomass and Vegetative Development
Mulched treatments significantly improved vegetative growth characteristics in both crops. Plants grown under black polyethylene mulch showed:
- Higher fresh biomass accumulation
- Increased dry matter production
- Greater plant height
- More branch formation
- Enhanced canopy development
The improvement in vegetative growth was primarily related to better soil moisture conservation, reduced water stress, and improved root-zone environmental conditions.
Higher moisture availability near the root system enhances nutrient uptake, photosynthesis, and metabolic activity, resulting in stronger plant growth throughout the growing season.
Influence of Black Polyethylene Mulch on Yield
Early and Total Yield Improvement
One of the most significant findings of the study was the substantial increase in crop yield under mulched conditions.
Both okra and squash produced significantly higher:
- Early yield
- Mid-season yield
- Late-season yield
- Total fruit yield
- Fruit number per plant
Mulched plots also demonstrated earlier productivity compared with non-mulched treatments. In okra, the early yield produced under mulching conditions was approximately equal to the total yield obtained from bare soil treatments, highlighting the strong positive impact of moisture conservation on crop performance.
The increase in total yield was associated with:
- Earlier seedling establishment
- Faster flowering
- Improved vegetative growth
- Better moisture availability
- Enhanced nutrient absorption
- Reduced weed competition
Fruit Development and Quality
Average fruit weight generally increased under black polyethylene mulch, particularly in squash plants. Improved hydrothermal soil conditions and reduced moisture stress contributed to better fruit growth and development.
The favorable microclimate created beneath the mulch layer supports continuous plant growth and reproductive development throughout the season.
Plastic mulching is considered an effective agricultural practice for conserving water in drought-prone environments. Soil evaporation can account for a large proportion of total water loss in agricultural systems, especially under hot and dry climatic conditions.
By covering the soil surface, black polyethylene mulch minimizes direct evaporation, helping maintain higher soil moisture levels during the growing season. The mulch layer also suppresses weeds, which reduces competition for water and nutrients.
Improved soil moisture and increased soil temperature under mulch treatments create favorable growing conditions that stimulate earlier plant development and flowering. These environmental improvements enhance physiological processes such as photosynthesis, nutrient uptake, and biomass accumulation.
Higher soil moisture availability also promotes root proliferation, allowing plants to access nutrients more efficiently. Consequently, mulched crops exhibit stronger vegetative growth and greater tolerance to drought stress during mid- and late-season development.
The higher yields observed in mulched plots are directly linked to improved water conservation, enhanced plant growth, and reduced environmental stress. Similar findings have been reported in studies involving tomato, hot pepper, watermelon, and other vegetable crops grown under polyethylene mulch systems.
In rain-fed semi-arid agriculture, maintaining sufficient moisture around the root zone is essential for stable crop production. Mulching technologies therefore represent an important tool for improving agricultural sustainability under water-limited conditions.
Conclusion
The results of this study clearly demonstrate the beneficial effects of black polyethylene plastic mulch on soil moisture conservation, plant growth, and yield performance of okra and squash grown under rain-fed semi-arid conditions.
Black polyethylene mulch significantly:
- Reduced soil water evaporation
- Improved soil moisture retention
- Accelerated seedling emergence
- Enhanced vegetative growth
- Promoted earlier flowering
- Increased total fruit yield
- Improved crop productivity under drought conditions
The findings suggest that polyethylene mulch can serve as an effective agricultural management practice for summer vegetable production in water-scarce environments.
For rain-fed farming systems in semi-arid regions, the use of black polyethylene mulch is strongly recommended to improve crop growth, enhance water use efficiency, and increase agricultural productivity. Future research should further investigate the performance of different mulch materials, colors, and biodegradable alternatives under rain-fed environmental conditions.