1 Introduction

Okra production in mid-hill regions such as East Rukum is often constrained by uneven topography, limited irrigation facilities, and moisture stress during dry periods. Farmers in this region largely depend on rainfall, and soil moisture conservation remains a major challenge affecting crop growth and yield stability (Adhikari, 2018). Under such conditions, vegetable production, including okra, is highly affected due to moisture stress and limited soil management options. In addition, the availability and use of mulching materials are not well optimized under local farming conditions (Atreya et al., 2008).

Okra, scientifically known as Abelmoschus esculentus, is a renowned species belonging to the family Malvaceae. It holds great economic value as a vegetable crop, primarily cultivated in tropical and subtropical regions across the globe. It serves not only as a valuable source of fiber and nutrients but also plays a significant role in promoting human health. In Nepal, the total production of okra is 13.7 Mt/ha (MoALD, 2024). It is widely cultivated in Jhapa, Morang, Saptari, Bara, Chitwan, Rautahat, Kailali, and Dhanusa (Jha et al., 2018).

Mulching is the agronomic practice of leaving mulch on the surface of the soil for soil and water conservation and to favor plants’ growth. Mulch refers to any material, other than soil or living vegetation, that performs the function of permanent or semi-permanent protective cover over the soil surface (Prosdocimi et al., 2016). When mulch is used, the soil becomes less compact and cooler, and its porosity and moisture improve. It also helps increase soil pH, organic matter, and the levels of nutrients like nitrogen, phosphorus, potassium, calcium, and magnesium in both the soil and the plant leaves (Adekiya et al., 2017). Mulching helps reduce weed growth, limits water loss through evaporation, and protects the soil from runoff and erosion, which together slow down soil degradation. As a result, it improves soil moisture retention, moderates soil temperature, enhances the soil’s physical, chemical, and biological properties, and ultimately supports healthier crop growth and higher yields (Chauhan et al., 2024). Generally, straw, rice husk, crop residues or plastic mulch can be used as artificial mulch in crops (Wilhoit et al., 2019). An effective mulch should be affordable, readily available, simple to apply, and durable enough to resist being washed or blown away (Norman et al., 2011). However, limited studies have been conducted on the effectiveness of different mulching materials under the specific agro-ecological conditions of East Rukum, where environmental constraints differ significantly from the lowland areas of Nepal.

Therefore, the objective of this study was to evaluate the effect of different mulching practices on the growth and yield of okra, and to compare the yield performance under each mulching treatment. The study aimed to identify the most effective mulching method for improving okra yield and to generate useful information that can help farmers select suitable mulching practices for better crop productivity.

2 Materials and Methods

2.1 Experimental site

The experiment was conducted from 10^th April to 24^th June, 2024, at Dhakalbara, Sisne Rural Municipality-6, East Rukum District. The geographical location of the site is situated at an elevation of 1,568 m above sea level; the latitude is 28.612,803,06 ºNorth, and the longitude is 82.620,663,89 ºEast. The soil was classified as sandy loam soil with a medium level of nitrogen and has an alkaline pH (Kafle et al., 2025).

2.2 Experimental details

The experiment was conducted using a randomized complete block design with 6 treatments, and each treatment was replicated 4 times. The Arka Anamika variety was selected for experimental purposes. The variety was brought from the local agrovet. Six treatments, i.e., T1-black plastic mulch, T2-control, T3-mustard straw, T4-banmara (Eupatorium adenophorum), T5-sawdust, and T6-leaf litter (Acacia catechu, Syzygium cumini, Cedrus deodara) were tested. The thickness of plastic mulch was 25 microns. 600 kilogram/ropani of decomposed farmyard manure were applied (Agriculture and Livestock Diary, 2081). Chemical fertilizers were not used as the site area consists of 100% organic farming practices.

2.3 Experimental unit

Each plot measured 2.1 m in length and 2.1 m in breadth. The R-R distance between crops was 30 cm, and the P-P distance was 30 cm. The individual plot area was 4.41 m² with 7 rows and 7 plants per row, giving a total of 49 plants in each plot. The distance between the blocks of replication was 50 cm, and within the treatments was 50 cm. The outer two rows and the outer two columns were designated as border plants, and data were recorded from the sample plants selected from the remaining inner area of the plot. Out of 7 rows, the outer 2 rows were taken as border plants, and the data were recorded from the sample plants selected within the remaining rows. The outer border was 50 cm from the plot.

2.4 Field preparation and layout

The field was ploughed using a mini tiller. Then the field was divided into 24 plots with each plot size of 2.1 m length and 2.1 m breadth in the appropriate layout of RCBD design. Measuring tape, pegs, and plastic ropes were used to carry out the layout of the field. Soil was treated with the recommended dose of Metarhizium biopesticides before sowing. Okra seeds were soaked in water for 24 hours and dried using a clean paper towel before sowing. 3 seeds per hill were sown in the field at a distance of 30 cm R-R distance and 30 cm P-P distance. Thinning of an extra 2 plants was done after satisfactory growth, leaving one behind. The okra seeds were sown on 20^th April, 2024.

2.5 Data collection and measurements

Except border plants, 10 plants were chosen at random from the net plot and tagged to record observations on growth and yield metrics. Plant height and number of leaves per plant were recorded as vegetative parameters. Plant height (cm) was measured from the base of the plant to the tip of the apex or flower. The number of fully developed fresh leaves attached to the plants was counted and recorded.

Yield-related parameters included average fruit length, average fruit weight, and productivity. The average fruit length (cm) was determined by measuring the length of the fruit (pod), including the pod stalk, at harvest and then averaging the values. The average fruit weight (g) was calculated by dividing the total weight of fruits harvested from 10 tagged plants by the number of fruits produced by those same plants. Productivity (Mt/ha) was estimated by converting the net plot yield, measured from 10 tagged plants, into metric tons per hectare.

2.6 Statistical analysis

The data obtained from the experiment were analyzed using Microsoft Excel 2019 and R-Studio (version 4.5.2). Mean comparisons were performed using Duncan’s Multiple Range Test (DMRT) and the Least Significant Difference (LSD) test at 5% level of significance (Gomez and Gomez, 1984).

3 Results and Analysis

3.1 Plant height (cm)

The mulching materials had a significant impact on plant height at 25, 40, and 60 days after sowing (DAS) (Table 1). At 25 DAS, the tallest plants (8.61 cm) were observed in plots mulched with black plastic; the leaf litter had the smallest plant height (5.89 cm). This treatment continued to produce the highest plant height at 40 days (22.37 cm) and 60 days (74.87 cm) after sowing. At 40 DAS, plant heights under mustard straw (20.17 cm) were statistically similar to those under black plastic mulch (22.37 cm). The leaf litter showed the lowest plant heights at 40 days (12.55 cm) and 60 days (53.97 cm). The results showed that black plastic mulch significantly increased plant height at all growth stages (25, 40 and 60 DAS), followed by mustard straw mulch, while leaf litter consistently resulted in the lowest plant heights throughout the growth period.

3.2 Leaf number

The mulching materials had a significant effect on leaf number at 25, 40, and 60 days after sowing (DAS) (Table 2). At 25 DAS, the highest number of leaves (5.48) was recorded in plots mulched with black plastic, whereas the lowest leaf number (4.51) was observed under banmara mulch. At this stage, all organic mulches and the control plot were statistically similar with respect to leaf number. At 40 DAS, black plastic mulch again produced the maximum leaf number (19.60). The control plot (14.58), mustard straw (13.48), and banmara mulch (14.28) were statistically comparable, while sawdust (9.98) and leaf litter (11.58) recorded the lowest leaf numbers. At 60 DAS, black plastic mulch (27.58) maintained the highest leaf number, while leaf litter resulted in the lowest leaf number (15.88). The control plot (20.58) and banmara mulch (20.78) showed statistically similar leaf numbers. Overall, the results indicated that black plastic mulch significantly increased leaf numbers at all growth stages (25, 40, and 60 DAS), followed by mustard straw and banmara mulches, whereas sawdust and leaf litter mulches consistently produced the lowest leaf numbers throughout the crop growth period.

3.3 Yield parameter and productivity

The results showed that the average fruit weight was highest (245.80 g) under black plastic mulch, which was significantly superior to mustard straw, banmara, sawdust, and leaf litter mulches, but statistically similar to the control plot (193.70 g) (Table 3). The lowest fruit weight (129.85 g) was recorded under leaf litter mulch. Average fruit length was also significantly affected by mulching. The longest fruits (14.91 cm) were obtained under black plastic mulch, followed by leaf litter (13.76 cm) and control plots (13.67 cm). The shortest fruits (12.88 cm) were recorded in mustard straw mulch. The productivity was highest under black plastic mulch (14.897 Mt/ha), followed by the control plot (11.739 Mt/ha), mustard straw (9.289 Mt/ha), banmara (9.831 Mt/ha), sawdust (8.433 Mt/ha), and leaf litter (7.87 Mt/ha), respectively. Increased productivity under black plastic mulch is likely associated with larger and longer fruits, higher fruit set, and improved microclimate conditions, leading to enhanced overall yield.

4 Discussion

The result presented in Table 1 shows that black plastic mulch had the tallest plant height at 25 DAS, 40 DAS, and 60 DAS. These findings are in accordance with (Chaudhary et al., 2023), who reported the highest plant height under black plastic mulch at each stage. At the beginning of the growing season, the remaining treatments did not show significant differences in plant height. The improved growth under black plastic mulch can be attributed to the effective suppression of weeds, which reduces competition between weeds and crop plants (Bhutia et al., 2017). A direct relationship between plant height and soil residual moisture has been reported, where moisture stress reduces plant growth, while mulching helps maintain favorable conditions (Otuaro et al., 2024). Furthermore, mulching creates stable soil physical conditions that promote root expansion and enhance nutrient uptake, thereby contributing to improved plant growth (Kamble et al., 2020).

Black plastic mulch significantly influenced the leaf number of okra at 25, 40, and 60 DAS, consistently producing the highest number of leaves across all growth stages. This trend aligns with findings from recent studies showing that plastic mulches, especially black plastic, improved vegetative growth characteristics in okra and other vegetable crops, such as leaf number (Chaulagain et al., 2024). On the other hand, organic mulches such as sawdust and leaf litter exhibited lower leaf numbers, particularly at 40 and 60 DAS. The comparatively weaker performance of organic mulches may be due to their limited ability to modify soil temperature and moisture conditions in the short term, which are critical for rapid vegetative growth (Kim et al., 2016).

The superior performance of black plastic mulch can be more broadly attributed to its regulation of the soil microenvironment. Modifying the soil energy balance and limiting evaporative losses, it creates conditions that favor rapid leaf initiation and expansion (Thakur et al., 2020; El-Beltagi et al., 2022).

The fruit characteristics and productivity of okra were significantly influenced by mulching. Black plastic mulch produced the highest average fruit weight (245.80 g), fruit length (14.91 cm), and productivity (14.897 Mt/ha), whereas the lowest fruit weight (129.85 g) and productivity (7.87 Mt/ha) were recorded under leaf litter mulch. This yield advantage under black plastic mulch can be linked to cumulative effects on plant growth, rather than a single factor, resulting in improved fruit size and development.

The superior fruit length observed under black plastic mulch is consistent with earlier findings that plastic mulches enhance fruit elongation through improved soil moisture conservation and temperature regulation (Thakur et al., 2020). Similar improvements in pod length were reported by Singh et al. (2025) and Godawatte and De Silva (2016), who associated this response with improved growing conditions under mulch.

In contrast, organic mulches generally showed limited or inconsistent effects on productivity, which may reflect their slower modification of the soil environment and delayed nutrient availability (Thakur et al., 2020; Chaulagain et al., 2024), as also observed in the present study.

In contrast to the present study, Adhikari et al. (2023) and Smith and Onamadi (2021) reported higher okra yield under organic mulches, mainly due to reduced weed competition. This variation among studies indicates that environmental conditions, moisture availability, and management practices influence the effectiveness of mulching materials.

5 Conclusion

The findings of this study support that the black plastic mulch consistently outperformed other mulching materials in enhancing the growth and yield of okra under the agro-climatic conditions of East Rukum, Nepal. Plants grown with black plastic mulch exhibited greater plant height and higher leaf number at all growth stages compared to other treatments. This enhanced vegetative growth contributed to improved yield attributes, resulting in higher fruit weight and longer fruits. Consequently, black plastic mulch produced significantly higher productivity, while leaf litter mulch resulted in the lowest yield performance. Overall, the use of black plastic mulch was found to be the most effective mulching practice for improving the growth and productivity of okra.

Authors’ contributions

Princess Magar conceived and designed the study, conducted the experiment, and collected the data. She also assisted with data analysis, statistical interpretation, and preparation of figures and tables. Jenisha Lama and Rakshya Devkota interpreted the results and contributed to manuscript writing. Jenisha contributed to the literature review and gathered relevant resources for manuscript development. Rakshya supervised the study, provided critical feedback, and improved the manuscript through suggestions and revisions. All authors read and approved the final manuscript.

Conflict of Interest Disclosure

The authors affirm that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest.

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