Non-chemical weed management in French bean (Phaseolus vulgaris L. Merrill)

Introduction

The French bean, scientifically known as Phaseolus vulgaris L. Merrill, is a common leguminous crop grown worldwide for its edible seeds and pods. It accounts for around 30% of the world's total food legume production (Vasishtha and Srivastava, 2012) [16] . French beans are member of the Fabaceae family. Filet beans, French green beans, fine beans, haricots verts, string beans, and snap beans are other names for this plant, which is native to Central and South America. According to Sinkovic et al. (2024) [17] , 100 grams of green pods have 1.9 grams of protein, 5.66 grams of carbs, 24 micrograms of vitamin A, 52.5 micrograms of vitamin K, 17 milligrams of calcium, and 2.6 grams of fiber. French bean is an essential crop for fostering food security and balanced diets because of their high nutritional density and low-calorie content. From 35.92 million hectares of land, around 27.72 million metric tons of French beans were produced worldwide in 2022. (Laskar et al., 2023) [11] . India leads the world in both French bean production and area, with 158.53 lakh hectares and 66.10 lakh tons, respectively followed by the countries Brazil, (Area-26.08 Lakh ha, Production-28.42 Lakh tons), Myanmar (Area-28.61 Lakh ha, Production-26.63 Lakh tons), Tanzania (Area-10.03 Lakh ha, Production-13.48 Lakh tons) and Uganda (Area-7.31 Lakh ha, Production-13 Lakh tons) in area and production both. But in productivity of French bean USA ranks first in world (Productivity-2388 kg/ ha), followed by Uganda (1785 kg/ha), China (1766 kg/ha) and Tanzania (1343 kg/ha). However, only 417 kg/ha are produced in India (Anonymous 2022) [1] . There are multiple states in India that cultivate French beans. The highest-producing state is Gujrat (production of 751.99), followed by Bihar (production of 244.55), Jharkhand (production of 200.82 tons), Karnataka (production of 166.76 tons), and Maharashtra (area of 5.5 thousand hectares, production of 69.95 tons). India has a large and promising region, but the production of French beans is quite low compared to other countries.

The low yield of French beans in India is linked to a lack of important production restrictions, such as, weed infestation and inadequate fertilizer application. Among those production limitations, the use of fertilizer resulted in yield losses of up to 34%, followed by weed infestation (13%) (Bansode et al., 2019) [3] . Among the above-mentioned restrictions, a significant one that prevents French beans from growing and producing as much as they could is the severe weed invasion. According to Chavan et al., (2020) [4] , the main weeds found in French beans include Euphorbia geniculata, Cynodon dactylon, Brachiaria eruciformis, Acalypha indica, camelina benghalensis, Digera arvensis, Convolvulus arvensis, and Cyperus rotundus. Due to their competition for resources such as light, water, soil nutrients and space (Dhaker et al., 2022) [5] these significant weeds can lower French bean yields. According to (Horvath et al., 2023) [6] , as longer the duration weeds compete with plant, lower the pods produces per plant (Jahanbakshi et al., 2015) [9] . Weed density is crucial because a greater problem is typically caused by more weeds rather than fewer weeds. Weed competition time is also crucial. Maintaining the crop free of weeds between 11 and 29 DAE can prevent yield losses of more than 5%. To increase yields, French bean growers must use more herbicides to control weeds. Weed infestations in croplands hence raise the cost of cultivation considerably. In addition to increasing the cost of inputs, extensive chemical use can harm the environment by causing problems including water contamination, retension of herbicide residue, weed resistance to herbicides (Mirza, et al., 2020) [12] . Alternative techniques like, solarization, bio-solarization and the use of smother crops present promising answers to the problem of weed infestations in croplands and minimize dependency on herbicides. In addition to lowering crop expenses, these sustainable approaches can also improve ecosystem health and lessen their negative effects on the environment (Jacob, et al. 2024) [7] . When compared to all other soil solarization treatments, the temperature of the soil has been considerably raised by black polythene mulch. In comparison to the nonmulched plot, the various soil solarization treatments, which resulted in increases in soil temperature due to covering, were 2 to 4 °C for 5 cm, 2 to 5 °C for 15 cm at 7:20 am, 4 to 8 °C for 5 cm, and 3 to 7 for 15 cm at 2:30 pm. (Jagtap et al., 2022) [8] Crop wastes are utilized in bio-solarization to prevent the growth of weeds. Crop residues can also improve soil quality in several ways when combined with efficient agricultural management approaches. They enhance soil structure, boost soil organic matter, lower evaporation and aid in the fixation of carbon dioxide (CO 2 ). Non-chemical weed management techniques can be essential in meeting the dietary needs of the average person, eradicating deficiency diseases and malnutrition, alleviating stress on cereals, promoting French bean production and reducing environmental degradation brought on by increased chemical use for weed control.

Materials and Methods

The field experiment was conducted at experimental farm, Department of Agronomy, College of agriculture, V.N.M.K.V. Parbhani (M.S) during kharif 2024. The site was located 19 0 16 ' North latitude and 76 0 47 ' East longitude and at 409 altitudes above mean sea level and has a semi-arid climate. The experiment was laid in Randomized Block Design (RBD) with 3 replications. The experiment comprises of 7 treatments viz., T 1soil solarization, T 2 -bio-solarization, T 3 -smother crop (Amaranth), T 4 -straw mulch 5 cm thickness, T 5 -straw mulch 7.5 cm thickness, T 6 -weedy check and T 7 -weed free. The soil of the experimental field was medium black and clay loam in texture and moderately alkaline in reaction (7.2 pH). The size of the gross and net plot was 5.4 m x 4.5 m and 4.5 m x 4.3 m, respectively. Plant protection measures were taken as per the recommended schedule. The major weeds associated with French bean were identified on the basis of cotyledons. The data collected on weed density were collected using 1m 2 quadrate (g m -2 ), weed dry weight were measured by using electric weighing balance and weed control efficiency was worked out by using the formula as below, Where, WCE = Weed control efficiency in%; DWC = weed dry weight in control plot; DWT= weed dry weight in treated plot. Data on various variables were analyzed by analysis of variance (Panse and Sukhatme, 1967) [13] . The data on weed control efficiency was further subjected to DMRT (Dunccan's Multiple Range Test).

Results and Discussion

Weed flora

During the experimental studies two types of weeds were observed depending on their cotyledons i.e. monocot and dicots. Table 1 showed major weeds associated with French bean observed during experimentation. Mainly monocots weeds are perennial weeds and dicot weeds are seasonal weeds. The major weed flora observed in the experimental field of French bean crop included monocot weeds were shippi (Brachiaria eruciformis), Kena (Commelina benghalensis), Hariyali (Cynodon dactylon), Lavala (Cyperus rotundus), Chimanchara (Digitaria sanguinalis) and dicot weeds were Gajargavat (Parthenium hysterophorus), Deepmal (Acalypha indica), Kunjru (Digera arvensis) and Tandulja (Amaranthus polygamous). Similar results were found by chavan et al., (2020) [4] .

The mean data on weed density of monocots, dicots and total weeds was recorded at 30, 45, 60 and 75 DAS were furnished in Table 2. The differences in monocots weed density were found to be significant at 30, 45, 60 and 75 DAS. The lower number of monocot weeds at 30 and 45 DAS were (3.00, 4.60) no m -2 respectively, recorded with T 1 -soil solarisation followed by T 7weed free i.e. 4.00, 7.00 no m -2 at 30 and 45 DAS respectively. This might be due to initial weed reductions with soil solarization was high. Similar result found by Corazon et al., (2024) [2] . However lower number of monocot weeds at 60 and 75 DAS were (3.00, 6.00 no m -2 ) respectively, recorded with T 3 -amaranth as smother crop followed by T 7 -weed free i.e. 7.00, 6.30 no m -2 at 60 and 75 DAS respectively. This might be due to smother crops inhibit weed emergence by rapidly covering the ground and releasing growth-inhibiting allelochemicals. This suggests that Amaranth is effective in weed suppression in early to mid-crop stages. Teasdale et al., (2007) [15] . Similar to monocots, dicots weed density was also significantly affected by non-chemical weed management treatments at 30, 45, 60 and 75 DAS. The lower number of dicot weeds recorded with T 1 -soil solarisation at 30 and 45 DAS were (3.47 and 6.00 no m -2 ) respectively. Followed by T 2 -biosolarization and T 3 -amaranth as smother crop (6.00, 7.00 no m -2 ) at 30 and 45 DAS respectively. Similar result found by Corazon et al., (2024) [2] . This might be due to reduction in weed density in solarization and bio-solarization treatments is attributed to the elevated soil temperatures which destroy weed seeds and emerging seedlings. Similar result found by Corazon et al., (2024) [2] . However lower number of dicot weeds at 60 and 75 DAS were (4.98, 5.77 no m - 2 ) respectively, recorded with T 3 -amaranth as smother crop followed by T 7 -weed free i.e. 6.00, 9.33 no m -2 at 60 and 75 DAS respectively. This might be due to smother crops inhibit weed emergence by rapidly covering the ground and releasing growth-inhibiting allelochemicals. Similar result found by Teasdale et al., (2007) [15] . Total weed density was also significantly affected by weed management treatments at 30, 45, 60 and 75 DAS. Soil solarisation (T 1 ) treatment recorded significantly lower number of total weeds (6.47, 10.60 no m -2 ) at 30 and 45 DAS respectively. This might be due to reduction in weed competition in solarization and bio-solarization treatments due to the increased soil temperatures which kills weed seedlings. Similar result found by Corazon et al., (2024) [2] . However treatment T 3 -amaranth as smother crop recorded significantly lower number of total weeds i.e. 7.96 no m -2 at 60 DAS and 12.07 no m -2 at 60, 75 DAS respectively. This might be due to smothering effect of amaranth on weed emergence. Similar result found by Teasdale et al., (2007) [15] . However T 6weedy check recorded highest weed density (monocots, dicots and total) at 30, 45, 60 and 75 DAS respectively.

Mean data on dry matter of monocots, dicots and total weeds recorded at 30, 45, 60, 75 DAS were furnished in Table 3. At 30 and 45 DAS all the weed management treatments recorded significantly lower total weed dry matter over weedy check. At 30 DAS significantly lower dry matter of monocot weeds was recorded by T 1 -soil solarisation (2.00 g m -2 ) followed by T 2 (Bio-solarization) i.e. 3.00 g m -2 and at 45 DAS significantly lower dry matter of monocot weeds was recorded by T 1 -Soil solarization (3.00) g m -2 followed by T 3 (Amaranth as smother crop) i.e. 5.00 g m -2 and T 7 (Weed free) i.e. 5.57 g m -2 . Significantly higher dry matter of monocot weeds was recorded in weedy check (T 6 ) treatment i.e. 15.00 g m -2 , 11.00 g m -2 at 30 and 45 DAS respectively. Similar to monocots, dry matter of dicot weeds was also significantly affected by weed management treatments at 30 and 45 DAS. At 30 DAS the lower dry matter of dicot weeds was recorded with T 1 -Soil solarization (5.00) g m -2 followed by T 4 (Straw mulch 5 cm thickness) i.e. 6.57 g m -2 . At 45 DAS lower dry matter of dicot weeds was recorded with T 1 -Soil solarization (6.03) g m -2 followed by T 2 (Bio-solarization) i.e. 6.43 g m -2 . Significantly higher dry matter of dicot weeds was recorded with weedy check (T 6 ) treatment i.e. 11.33 g m -2 , 12.00 g m -2 at 30 and 45 DAS respectively. Similar results were found by Teasdale et al., (2007) [15] and Shinde et al., (2023) [14] reported that soil solarization significantly reduces the initial weed seed bank in the soil. The reduction in weed density in solarization and bio-solarization treatments is attributed to the elevated soil temperatures which destroy weed seeds and emerging seedlings these results in reduced weed dry matter. Dry matter of total weeds was also significantly affected by weed management treatments at 30 and 45 DAS. Significantly the lower dry matter of total weeds at 30 DAS (7.00 g m -2 ) were recorded with T 1 -soil solarization followed by T 2 (Biosolarization) i.e. 10.00 g m -2 . At 45 DAS significantly the lower dry matter of total weeds (9.03 g m -2 ) were recorded with T 1 -Soil solarization followed by T 3 (Amaranth as smother crop) i.e.

12.00 g m -2 . Significantly higher dry matter of total weeds recorded with weedy check (T 6 ) treatment i.e. 18.77 g m -2 , 23.00 g m -2 at 30 and 45 DAS. At 60 DAS dry matter of monocot weeds significantly influenced by weed management treatments. Significantly lower dry matter of monocot weeds was reduced by T 3 -Amaranth as smother crop (3.00) g m -2 followed by T 2 (Bio-solarization) i.e. 6.00 g m -2 and T 5 (Straw mulch 7.5 cm thickness) i.e. 6.00 g m -2 . Significantly higher dry matter of monocot weeds recorded in weedy check (T 6 ) treatment i.e. 18.01 g m -2 . Similar to monocots, dry matter of dicot weeds was also significantly affected by weed management treatments at 60 DAS. The lower dry matter of dicot weeds was recorded with T 3 -Amaranth as smother crop (5.97) g m -2 followed by T 1 (Soil solarization) i.e. 7.80 g m -2 and T 7 -weed free (7.83) g m -2 . Significantly higher dry matter of dicot weeds recorded in weedy check (T 6 ) treatment i.e. 11.53 g m -2 . Dry matter of total weeds was also significantly affected by weed management treatments at 60 DAS. Significantly the lower dry matter of total weeds (8.97 g m -2 ) were recorded with T 3 -Amaranth as smother crop followed by T 5 (Straw mulch 7.5 cm thickness) i.e. 10.53 g m -2 . Significantly higher dry matter of total weeds recorded in weedy check (T 6 ) treatment i.e. 29.54 g m -2 at 60 DAS. Similar results were found by Kiran et al., (2022) [10] . This might be due to weed suppression efficiency of nonchemical weed management methods such as smother crop-Amaranth and mulching remains significant even in the later stages of crop growth. At 75 DAS dry matter of monocot weeds significantly influenced by weed management treatments. Significantly lower dry matter of monocot weeds was reduced by T 3 -Amaranth as smother crop (3.00) g m -2 followed by T 7 (Weed free) i.e. 5.30 g m -2 and T 1 (Soil solarization) i.e. 7.00 g m -2 . Significantly higher dry matter of monocot weeds recorded in weedy check (T 6 ) treatment i.e. 15.00 g m -2 . Similar to monocots, dry matter of dicot weeds was also significantly affected by non-chemical weed management treatments at harvest. The lower dry matter of dicot weeds was recorded with T 3 -Amaranth as smother crop (5.00) g m -2 followed by T 2 (Bio-solarization) i.e. 8.50 g m -2 . Significantly higher dry matter of dicot weeds recorded in weedy check (T 6 ) treatment i.e. 17.10 g m -2 . Similar findings were reported by Kiran et al., (2022) [10] . This might be due to smother crop releases allelo-chemicals which suppresses weed growth. Dry matter of total weeds was also significantly affected by nonchemical weed management treatments at harvest. At 75 DAS, significantly the lower dry matter of total weeds (8.00 g m -2 ) were recorded with T 3 -Amaranth as smother crop followed by T 7 (Weed free) i.e. 15.33 g m -2 . Significantly higher dry matter of total weeds recorded in weedy check (T 6 ) treatment i.e. 32.10 g m -2 .

The data regarding treatment means for weed control efficiency of monocot and dicot weeds were grouped using Duncan's Multiple Range Test (DMRT) at 30, 45, 60 and 75 DAS were furnished in Table 4. At 30 DAS, the highest weed control efficiency of monocot weeds was recorded under T 1 (Soil solarization) with 81.81%, falling in group (a) and was thus the most effective treatment for monocot suppression. It was followed by T 2 (Bio-solarization) with 72.72% efficiency, grouped under (ab), indicating slightly lower but comparable performance with T 1 -soil solarization. T 5 (Straw mulch 7.5 cm thickness) and T 7 (Weed free) recorded moderate weed control efficiency for monocot weeds i.e. (63.63% and 62.72% respectively) grouped under (bc), indicating reasonable effectiveness. The smother crop treatment (T 3 ) and T 4 (Straw mulch 5 cm) had relatively lower weed control efficiency, with T 3 (54.54%) in group (c) and T 4 (36.36%) in group (d), showing lesser effectiveness for monocot weed suppression. The highest weed control efficiency for dicot weeds (55.86%) was observed in both T 1 (Soil solarization) and T 4 (Straw mulch 5 cm thickness), grouped under (a), suggesting that both treatments were highly effective in reducing dicot weed population. T 5 (Straw mulch 7.5 cm) recorded 47.04% weed control efficiency grouped under (ab), and was followed by T 7 (Weed-free) (41.12%) in group (b). T 2 (Bio-solarization) was less effective against dicot weeds (38.21%), grouped under (bc). The lowest weed control efficiency (13.56%) was recorded in T 3 (Amaranth as smother crop), grouped under (c). Similar findings reported by Shinde et al., (2023) [14] who confirmed the efficacy of solarization in reducing early weed emergence. At 45 DAS, the highest weed control efficiency of monocot weeds was recorded under T 1 (Soil solarization) with 80.00%, falling in group (a) and was thus the most effective treatment for monocot suppression. The next best treatment were T 3 (Biosolarization) and T 5 (Straw mulch 7.5 cm thickness) with 66.66% weed control efficiency, grouped under (b). T 4 (Straw mulch 5 cm thickness) and T 7 (Weed free) recorded moderate weed control efficiency for monocot weeds i.e. (60.00% and 62.86% respectively) grouped under (bc), indicating reasonable effectiveness. The smother crop treatment (T 3 ) recorded relatively lower weed control efficiency (53.33%) and grouped under (c). The highest weed control efficiency for dicot weeds was observed in T 1 (Soil solarization) (49.75%), T 2 (Bio-solarization) (46.41%), T 3 (Amaranth as smother crop) (41.66%) and T 7 (weed free) (38.33) grouped under (a), suggesting that these treatments were highly effective in reducing dicot weed population. T 4 (Straw mulch 5 cm) recorded 25.38% weed control efficiency grouped under (b) and T 5 (Straw mulch 7.5 cm thickness) was least effective against dicot weeds (11.41%), grouped under (c). This might be due to the use of Amaranth as a smother crop which was not only competes for resources but also releases allelo-chemicals, thereby suppressing weed growth, particularly broadleaf species. During the experiment, at 60 DAS the higher weed control efficiency (83.34%) for monocot weeds was recorded by treatment T 3 (Amaranth as smother crop) which was grouped under (a). treatment T 2 (Bio-solarization) recorded 66.68%, T 5 (Straw mulch 7.5 cm thickness) recorded 66.68% weed control efficiency and T 7 (Weed free) recorded 62.40% WCE which was in group (b) which was followed by T 1 (Soil solarisation) recorded (61.13%) weed control efficiency for monocot grouped in (bc) and lower weed control efficiency (50.02%) was recorded with T 4 (Straw mulch 5 cm thickness) grouped in (c) group. The highest weed control efficiency for dicot weeds was observed in T 3 (Amaranth as smother crop) (48.22%). Weed control efficiency of T 1 (Soil solarization) and T 7 (weed free) was (32.35, 32.09%) respectively grouped under (b) which was followed by T 2 (Bio-solarization) and T4 (Straw mulch 5 cm thickness) with (21.94%) WCE grouped under (bc). T 5 (Straw mulch 7.5 cm thickness) was least effective against dicot weeds (17.34%) grouped under (c). The similar results were obtained to confirm the long-term effectiveness of the smother crop, which was reported by Kiran et al., (2022) [10] , this might be due to smother crops maintain their competitiveness during the entire growth cycle, thereby reducing weed pressure effectively. At 75 DAS, the higher weed control efficiency (80.00%) for monocot weeds was recorded by treatment T 3 (Amaranth as smother crop). Weed control efficiency for T 5 (Straw mulch 7.5 cm thickness) was 64.66% and for T 7 (weed free) was 60.00% both are grouped under (b) which was followed by treatment T 1 (Soil solarization) with 53.33% WCE. Treatment T 2 (Biosolarization) recorded 46.66% WCE grouped under (c). However the lower weed control efficiency (26.66%) for dicot weeds was recorded by treatment T 4 (Straw mulch 5 cm thickness) grouped under (d) group. The highest weed control efficiency for dicot weeds was observed in T 3 (Amaranth as smother crop) (70.76%). The next best treatments were T 2 (Biosolarization) with (50.29%) WCE, T 1 (Soil solarization) with 48.12% WCE, T 4 (Straw mulch 5 cm thickness) with 47.36% WCE, T 5 (Straw mulch 7.5 cm thickness) with 42.51% WCE, and T 7 (Weed free) with 41.34% WCE grouped under (b). The similar findings were reported by Shinde et al., (2023) [14] . This might be due to consistent performance of the smother crop till harvest indicates its utility not just for early weed suppression but also for full-season control. In French bean lower weed density, lower weed dry weight, higher weed control efficiency and weed suppression was attained through T 1 -soil solarization, T 2 -bio-solarization and T 3smother crop (Amaranth).

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