Eco-friendly weed management for enhancing fruit yield and soil chemical properties of watermelon

Introduction

Weeds are among the major biological constraints to crop production because they compete with crops for moisture, nutrients, light and physical space. Weed management is particularly challenging in organic production systems, where synthetic herbicides are restricted and greater reliance is placed on preventive, cultural and mechanical tactics. Organic farming practices have been associated with environmental benefits, although their effects vary with management system, soil conditions and production objectives (Gomiero et al., 2011) [1] . Non-chemical weed management is most effective when multiple tactics are integrated rather than relying on a single intervention (Bond et al., 2001; Liebman et al., 2009) [2,3] . More broadly, weed communities respond to crop rotation, residue cover, crop density, soil disturbance and other management factors, supporting the use of integrated strategies that suppress weed establishment and reduce the opportunity for seed production (Nichols et al., 2015; Chauhan, 2020) [5,4] . Mulching is particularly relevant to vegetable production because a soil-covering material can physically restrict weed emergence while modifying soil moisture and temperature. Plastic mulches have been associated with improved watermelon yield and water-use efficiency in environments where water is limiting, whereas organic and biodegradable mulches can suppress weed emergence while returning carbon-containing residues to the soil (Wang et al., 2011; Parmar et al., 2013; Gürbüz et al., 2023) [7,8,6] . The performance of organic mulches depends on the material, application rate, thickness, decomposition characteristics and weed flora present. Organic mulches can suppress weed emergence while conserving soil moisture and protecting the soil surface, making them particularly relevant to organic vegetable production (Schonbeck, 2012) [9] . Organic management practices can improve soil fertility through enhanced nutrient cycling and organic matter inputs, with long-term organic systems also showing improvements in soil biological and fertility-related properties (Mäder et al., 2002) [10] . Residue-based management may also influence soil chemical properties. [12,13,11] . Such effects provide a rationale for evaluating weed-management practices not only for crop productivity but also for their implications for soil chemical fertility. Watermelon (Citrullus lanatus) is an important cucurbit crop in India, and its sprawling growth habit leaves substantial soil surface exposed during early crop establishment. Consequently, weed interference can be severe before sufficient canopy development. Previous watermelon studies have demonstrated significant effects of mulching on growth, yield and weed suppression (Parmar et al., 2013; Gürbüz et al., 2023) [8, 6] . However, comparative information on locally available organic residues, cultural practices and their associated effects on soil pH, EC and CEC under Telangana conditions remains limited. The present study therefore evaluated nine weed-management treatments over two consecutive seasons, with emphasis on fruit yield and selected soil chemical properties.

Materials and methods

Experimental site and design

The field experiment was conducted during 2022-23 and 2023-24 at the AICRP on Weed Management Block, College Farm, Professor Jayashankar Telangana Agricultural University, Rajendranagar, Hyderabad, Telangana, India. The soil was sandy loam with an initial pH of 7.6, organic carbon of 0.76%, bulk density of 1.5 g cm⁻³, available nitrogen of 255 kg ha⁻¹, available phosphorus of 18.1 kg ha⁻¹ and available potassium of 615 kg ha⁻¹. The experiment followed a randomized block design with three replications. The experiment was conducted under organic production practices; however, pendimethalin was included in T 9 as a chemical comparison. Accordingly, T 9 is treated here as a conventional chemical comparator and is not considered an organic treatment. The supplied experimental record does not specify the watermelon cultivar, plot dimensions, irrigation schedule or organic-certification status; these details should be verified from the field record before journal submission.

Weed-management treatments 2.3 Fruit-yield measurement and plant nutrient analysis

Fruits were harvested at the marketable stage and fruit yield was expressed in tonnes per hectare. Plant samples collected at fruiting were dried, pulverized and analysed for total nitrogen, phosphorus and potassium. Nitrogen was determined using the micro-Kjeldahl procedure after acid digestion; phosphorus was estimated by the vanadomolybdophosphoric acid method after tri-acid digestion at 420 nm; and potassium was determined using a flame photometer. The analytical procedures followed Piper (1945) [14] .

Treatment Description

T 1 Groundnut-shell mulch @ 5 t ha -1 T 2

Rice-husk mulch @ 3 t ha -1 T 3

Polythene mulch + intra-row hand weeding at 30 DAS T 4

Rice-straw mulch @ 5 t ha -1 followed by intra-row hand weeding at 30 DAS T 5 Hoeing twice at 15 and 30 DAS T 6 Fenugreek green-leaf vegetable intercrop followed by hand weeding at 30 DAS T 7 Tamarind-leaf aqueous extract @ 10% at 3 and 20 DAT followed by hand weeding at 30 DAS T 8 Unweeded control

Treatment Description T 9 Pendimethalin 30% EC @ 1.0 kg a.i. ha -1 followed by hand weeding at 30 DAS

Soil sampling and analysis

Composite soil samples were collected randomly using a soil auger before sowing and after harvest from each plot. Samples were thoroughly mixed, air-dried, crushed and passed through a 2-mm sieve before analysis. Soil pH was measured in a 1:2.5 soil-to-water suspension using a digital pH meter. Electrical conductivity was measured in the corresponding supernatant using a digital conductivity meter. Cation exchange capacity was determined by ammonium acetate saturation followed by replacement of adsorbed ammonium with potassium chloride and distillation-based estimation, following the methods described by Jackson (1973) [15] .

Statistical analysis

Data were subjected to analysis of variance appropriate for a randomized block design following Gomez and Gomez (1984). Treatment means were compared using the critical difference (CD) at the 5% probability level when the F-test was significant. Non-significant differences were denoted as NS.

Results and discussion

Fruit yield

Weed-management practices significantly influenced watermelon fruit yield in both seasons (Table 1; Fig. 1). During 2022-23, T 3 (Polythene mulch + intra-row hand weeding at 30 DAS) recorded the highest fruit yield of 34.27 t ha -1 , followed by T 4 (rice-straw mulch + hand weeding) with 33.97 t ha -1 . The difference between T 3 and T 4 was only 0.30 t ha -1 , which was smaller than the CD of 2.96 t ha -1 , indicating that the two treatments were statistically at par. T 9 produced 17.57 t ha -1 , while T 1 , T 2 , T 5 , T 6 and T 7 produced 16.44, 8.59, 10.82, 10.12 and 7.75 t ha -1 , respectively. The unweeded control produced only 0.91 t ha -1 . During 2023-24, T 3 again recorded the highest yield (36.64 t ha -1

), followed by T 4 (34.64 t ha -1 ). Their numerical difference was 2.00 t ha -1 , which was smaller than the CD of 3.21 t ha -1 ; hence, the two treatments were statistically at par. T 9 produced 18.21 t ha⁻¹, whereas the unweeded control produced 1.09 t ha -1 . The large yield advantage under T 3 and T 4 is consistent with the expected effects of mulch cover and timely weed removal in reducing competition for soil moisture, nutrients, light and space. The response agrees with earlier watermelon research showing that mulching can improve crop performance by modifying soil moisture and temperature and by suppressing weeds. Parmar et al. (2013) [8] reported significant effects of different mulching materials on watermelon growth, yield and quality, while Wang et al. (2011) [7] showed that plastic mulch combined with rainwater-harvesting configurations could improve watermelon water-use efficiency and yield in a semiarid environment. More recently, Gürbüz et al. (2023) [6] demonstrated that biodegradable mulches could reduce weed pressure and affect watermelon fruit yield. The present results extend these observations by showing that locally available rice straw, when integrated with hand weeding, produced yield statistically comparable to polythene mulch in both seasons. The very low yield under T 8 emphasizes the magnitude of weed interference when no weed-control intervention is imposed. This is consistent with the broader weed-management literature, which emphasizes that crop competition, mulching, cultivation and hand weeding can act cumulatively and that integrated strategies are often more dependable than isolated measures (Bond et al., 2001; Liebman et al., 2009; Chauhan, 2020) [2,3,4] .

Soil pH

Soil pH was not significantly influenced by the weed-management treatments in either season (Table 2). In 2022-23, pH ranged from 7.67 to 8.06, with the lowest value under T 3 and the highest under T 8 .

In 2023-24, pH ranged from 7.53 to 8.01, with T 3 recording the low est value and T 5 the highest. The absence of a significant treatment effect indicates that the evaluated weed-management practices did not materially alter soil reaction over the period represented by the experiment. The relatively stable pH is also consistent with the observation that soil pH responses to organic management and amendments can depend strongly on initial soil condition, amendment chemistry and duration of management (Suja et al., 2017; Urra et al., 2019) [16,17] .

Figure 1.

Fruit yield of watermelon as influenced by eco-friendly weed-management practices.

Soil electrical conductivity

Soil EC was significantly affected by weed-management practices in both seasons. In 2022-23, EC ranged from 0.25 to 0.70 dS m -1 . The highest EC was recorded under T 3 (0.70 dS m -1

), whereas T 8 recorded the lowest value (0.25 dS m -1 ). In 2023-24, EC ranged from 0.19 to 0.91 dS m -1 , with T 3 again recording the highest value and T 8 the lowest. The higher EC under mulch treatments may reflect differences in nutrient cycling, residue decomposition and retention of soluble ions in the surface soil. However, EC is influenced by several interacting factors, and the present experiment did not measure individual soluble ions; therefore, the mechanism should be interpreted cautiously rather than attributed solely to decomposition.

Cation exchange capacity

CEC differed significantly among treatments in both seasons. During 2022-23, CEC ranged from 30.00 to 38.48 cmol(p⁺) kg -1 , whereas in 2023-24 it ranged from 30.49 to 39.06 cmol(p⁺) kg -1 . T 4 (rice-straw mulch + hand weeding) recorded the highest CEC in both seasons (38.48 and 39.06 cmol(p⁺) kg -1 , respectively). T 1 and T 6 also recorded comparatively high CEC values. The unweeded control recorded the lowest CEC in 2022-23 and a low value in 2023-24. T 9 and T 3 were intermediate. The relatively higher CEC associated with rice-straw mulch is biologically plausible because repeated organic-residue inputs can contribute organic matter and functional exchange sites. Organic-residue inputs can contribute to the stabilization and accumulation of soil organic matter, which may subsequently influence nutrient-retention characteristics and soil exchange capacity (Six et al., 2002) [18] . Organic inputs have been associated with changes in soil carbon pools and nutrient-retention characteristics, although the magnitude and direction of response depend on soil texture, amendment quality and management duration (Reganold et [12,17,11] . Importantly, the present experiment measured CEC but did not quantify soil organic carbon after treatment, so the proposed relationship between rice-straw addition and CEC should be regarded as a plausible interpretation rather than a directly demonstrated causal pathway.

Conclusion

The two-year field experiment demonstrated that weed-management practices strongly influenced watermelon fruit yield and selected soil chemical properties. Polythene mulch combined with intra-row hand weeding at 30 DAS produced the highest fruit yield in both seasons, but its yield was statistically at par with rice-straw mulch at 5 t ha -1 followed by hand weeding. Rice-straw mulch also recorded the highest CEC in both seasons, whereas soil pH remained statistically unchanged. EC was significantly affected by treatment, with the highest values under Polythene mulch plus hand weeding. The unweeded control resulted in very low fruit yield in both seasons, emphasizing the importance of effective weed suppression during watermelon production. Under conditions where synthetic herbicides are restricted, rice-straw mulch integrated with timely hand weeding provides a residue-based weed-management option that combines effective weed suppression with the potential to maintain soil chemical fertility.

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19. How to cite this article: Srija M, Padmaja B, Reddy MM, Prakash TR, Reddy MV, Venkatram A, et al. Eco-friendly weed management for enhancing fruit yield and soil chemical properties of watermelon. International Journal of Advanced Biochemistry Research. 2026;10(9S):1541-1545. doi: https://ww w.doi.org/10.33545/26174693.2026.v10.i9S.10042