Weed management practices influence productivity and profitability in kharif Greengram (Vigna radiata L.)

Introduction

Greengram [Vigna radiata (L.) Wilczek] also known as moong bean is one of the important pulse crop of India, belonging to the family Leguminosae and subfamily Papilionaceae. It has been reported that greengram has been cultivated in India since ancient times. It is believed that greengram is a native of India and Central Asia and grown in these regions since prehistoric times. Greengram is a fairly good source of some dietary minerals. The total minerals content in greengram is to the tune of 3.5 percent. Greengram seeds contain 22-28% protein, 60-65% carbohydrates, 1.0-1.5% fat, 3.5-4.5% fibre and 4.5-5.5% ash (Anon., 2019) [3] . Among the array of biotic and abiotic factors, weed infestation emerges as the primary biotic factor contributing to the reduced productivity of greengram in India. The potential yield loss in greengram due to weed has been estimated in the range of 10-45% (Rao and Chauhan, 2014) [26] . The critical period of crop-weed competition in greengram has been pinpointed as occurring from 15 to 30 days after sowing, with weed presence beyond this period resulting in significant losses in greengram yield (Mandal et al., 2006) [21] . Competition with the weeds led to 30 to 80% grain yield reduction in greengram during summer and kharif seasons, while 70-80% during rabi season (Algotar et al., 2015) [1] . Use of herbicides in conjunction with cultural practices or other practices would make complete control of weeds and will be acceptable by the poor farmer (Ayansina et al., 2003) [4] . Application of different straw mulches, soil solarization and stale seedbed have been found efficient in managing weeds. Hence, development of an integrated weed management is economically viable as well as ecologically safe for effective weed control and enhances the productivity of greengram.

Materials and Methods

The field experiment was conducted on Plot No. C-6 at Agronomy Instructional Farm, Department of Agronomy, Chimanbhai Patel College of Agriculture, Sardarkrushinagar Dantiwada Agricultural University, Sardarkrushinagar, Banaskantha (Gujarat) to investigate effect of weed management practices on kharif greengram. The soil of experimental field was loamy sand in texture with low in organic carbon (0.25%) and available nitrogen (148.0 kg/ha), medium in available phosphorus (38.6 kg/ha) and available potassium (252.4 kg/ha) having pH value of 7.45. The experiment was laid out in Randomized Block Design with three replications. The treatments comprised of ten methods of weed management viz., T 1: Soil solarization fb castor shell mulch @ 7.5 t/ha at 10 DAS, T 2: Soil solarization fb mustard straw mulch @ 5 t/ha at 10 DAS, T 3: Soil solarization fb interculture and hand weeding at 40 DAS, T 4: Stale seedbed fb castor shell mulch @ 7.5 t/ha at 10 DAS, T 5: Stale seedbed fb mustard straw mulch @ 5 t/ha at 10 DAS, T 6: Stale seedbed fb interculture and hand weeding at 40 DAS, T 7: Imazethapyr 100 ml/ha as PoE at 15 DAS, T 8: Imazethapyr 100 ml/ha as PoE at 15 DAS + interculture fb hand weeding at 40 DAS , T 9: Weed free, T 10: Unweeded check. Greengram variety 'GM 4' was sown on 18 th July, 2023 and fertilized with 20-40-00 kg N-P 2 O 5 -K 2 O/ha. The crop was grown with recommended package of practices for south Gujarat Agro-climatic Zone and was harvested on 09 th October, 2023. The sedges, grasses, broad leaf weeds were uprooted from 0.25 m 2 (50 cm × 50 cm) area in ring area of plots. The protein content in various samples was determined as a percentage using an NIR (Near-Infrared) spectroscopy device made by Dicky John Company (USA). The protein yield (kg/ha) was computed by using following formula, Protein yield (kg/ha) = Protein content in seed (%) x Seed yield (kg/ha) 100

Results and Discussion

Effect on weed parameters

The major weed species found in the experimental field at various stages were: [32] also supported these findings and claimed that weed free treatment resulted in lowest weed density and dry weight of weeds. Moreover, stale seedbed fb castor shell mulch @ 7.5 t/ha at 10 DAS and stale seedbed fb mustard straw mulch @ 5 t/ha at 10 DAS have also witnessed significantly lower dry weight of sedges, grasses, broad leaf and total weeds which was due to lower weed count of category wise and total weeds observed in those plots because of effective suppression of weeds by stale seedbed and mulching practices at initial phase. The findings are in conformity with results obtained by Mathukia et al. (2017) [22] who recorded that stale seedbed recorded significantly lowest dry weight of weeds, followed by soil solarisation. These findings were also further supported by Joshi et al. (2020) [15] . Whereas, at initial stage application of imazethapyr 100 ml/ha as PoE at 15 DAS and imazethapyr 100 ml/ha as PoE at 15 DAS + interculture fb hand weeding at 40 DAS treatments damaged the aceto lactate synthase (ALS) enzyme in the targeted weed plants which ultimately stopped amino acids synthesis resulting in suppression of broad leaf, sedges and grasses weeds. Further, Lal et al. (2018) [19] , Singh et al. (2015 a ) [32] and Goud et al. (2014) [11] also observed lower dry weight of weeds due to application of imazethapyr. The higher dry weight of weeds observed under the unweeded check treatment was a result of unchecked weed growth due to the absence of any weed control measures. Similar observations have also been reported by Chandolia et al. (2010) [5] , Meena et al. (2011) [23] and Jagadesh et al. (2019) [13] .

The analysis of data concerning the dry weight of weeds at 50 DAS and at harvest, under the influence of various weed management practices, emphasized that weed free treatment resulted in markedly reduced dry weight of sedges, grasses, broadleaf, and total weeds. Further, imazethapyr 100 ml/ha as PoE at 15 DAS + interculture fb hand weeding at 40 DAS demonstrated significantly lower weed dry weight of sedges, grasses, broadleaf, and total weeds and was found at par with stale seedbed fb interculture and hand weeding at 40 DAS. Whereas, higher weed dry weights noticed in other treatments was because of higher population of weeds recorded under these treatments. Wherein, significantly higher weed dry weight of different categories weeds like sedges, grasses, broadleaf, and total weeds were observed under the unweeded check condition.

Effective control of weeds under the above-mentioned treatments might have resulted in less dry weight of weeds. Under weed free treatment significantly lower weed density was reported at 50 DAS and at harvest due to complete control of weeds at these stages resulting in lower weed dry weight. The similar findings were also supported by Ali et al. (2011) [2] , Goud et al. (2014) [11] and Yadav et al. (2018). Further, the correlation and regression studies indicated that there was straight positive correlation between total weed density and total weed dry weight at 50 DAS and at harvest with correlation coefficients of 0.9989** and 0.9992**, respectively. In addition, the regression models indicated that every unit (1/m 2 ) increase in weed density shall increase the weed dry weight by 0.65 g/m 2 at 50 DAS and 0.64 g/m 2 at harvest, respectively. Thus, there was perfect positive relationship between weed density and weed dry weight at 50 DAS and at harvest. Jain et al. (2022) [14] observed that stale seedbed + hoeing with power weeder at 20 DAS + hoeing once at 40 DAS, stale seedbed + hoeing once at 20 DAS + application of 5 t/ha of straw mulch at 30 DAS recorded significantly lowest mean biomass of broad leaf weeds, grasses and sedges and total weeds at 30 DAS and 50 DAS. The combined effect of herbicide and hand weeding + inter-culturing ultimately resulted in minimum dry weight as observed by Raut et al. (2018) [28] . Significantly, lower sedges, grasses, broad leaf and total weed dry weights witnessed under imazethapyr 100 ml/ha as PoE at 15 DAS + inter-culture fb hand weeding at 40 DAS may be owing to effective suppression of all the category wise and total weeds up to 40 DAS by inhibition of ace to lactate synthase enzyme involved in protein synthesis in weeds and hence those density and dry weight were reduced. Subsequently, the interculture fb hand weeding at 40 DAS was further killed all the standing weeds by physical action resulting in lower weed density at 50 DAS and at harvest. The lower category wise and total weed dry weights witnessed under stale seedbed fb interculturing and hand weeding at 40 DAS may be an account of mostly emptying of all the weed seeds present in top 2-3 cm soil layer by stale seedbed effect and further killing of established weeds by interculturing and hand weeding practice at 40 DAS. Whereas, at all the stages significantly higher weed dry weight of category wise and total weeds were recorded under unweeded check because of poor control of weeds like sedges, grasses, broadleaf, and total weeds due to no weed control execution as described above in these treatments. These findings are in close proximity with findings of Singh et al.

(2009) [30] , Godara et al. (2014) [10] and Gelot et al. (2017) [9] .

Effect on growth parameters and yield

At 25 DAS, weed free treatment recorded significantly highest plant height as compared to other treatments. Next to weed free treatment, stale seedbed fb castor shell mulch @ 7.5 t/ha at 10 DAS witnessed significantly higher plant height which was statistically at par with stale seedbed fb mustard straw mulch @ 5 t/ha at 10 DAS, imazethapyr 100 ml/ha as PoE at 15 DAS, imazethapyr 100 ml/ha as PoE at 15 DAS + interculture fb hand weeding at 40 DAS, soil solarization fb castor shell mulch @ 7.5 t/ha at 10 DAS and soil solarization fb mustard straw mulch @ 5 t/ha at 10 DAS due to control of weeds by chemical and cultural weed management practices in these treatments resulting in lower weed density and weed dry weight observed in these treatments and hence realized higher plant height. Whereas, unweeded check reported significantly lower plant height which was found statistically at par with soil solarization fb interculture and hand weeding at 40 DAS and stale seedbed fb interculture and hand weeding at 40 DAS. This was due to higher density of sedges, grasses and broad leaf weeds noticed under these treatments due to lack of any weed management practices at initial stage which caused severe competition with crop. [25] , Singh et al. (2015 b ) [33] , Verma et al. (2017) [34] , Mathukia et al. (2017) [22] , Leva et al. (2018) [20] , Hajari et al. (2020) [12] . Whereas, significantly lower plant height in unweeded check, imazethapyr 100 ml/ha as PoE at 15 DAS, soil solarization fb mustard straw mulch @ 5 t/ha at 10 DAS, soil solarization fb castor shell mulch @ 7.5 t/ha at 10 DAS might be due to poor weed control in these treatments resulting in serious competition between crop and weed for moisture, nutrient, light and space. The results are in conformity with observations of Sharma and Yadava (2006) [29] and Rathi et al. (2008) in greengram. Lowest number of branches per plant were observed under unweeded check was mainly due to higher weed densities of sedges, grasses, broad leaf weeds and total weeds resulting in lower weed control efficiency and higher crop-weed competition. The similar consequences were also witnessed by Singh et al. (2010) [31] , Chhodavadia et al. (2013) [7] . Significantly higher seed yield recorded under T 9: weed free, Further, T 8: imazethapyr 100 ml/ha as PoE at 15 DAS + interculture fb hand weeding at 40 DAS and T 6: stale seedbed fb interculture and hand weeding at 40 DAS were directly attributed to significantly higher growth, yield parameters and stover yield recorded under these treatments viz., pod yield per plant and stover yield. These results are in concurrence with Leva et al. (2018) [20] who witnessed higher growth attributes, yield attributes and yield of greengram under weed free treatment but it was at par with imazethapyr 100 g/ha as PoE at 20 DAS + interculture fb hand weeding at 40 DAS. This might be due to effective control of weeds resulting in lesser competition from weeds on growth in these treatments. This facilitates the greengram crop to utilize more moisture, nutrients and solar radiation. Higher growth and resource utilization may turned into more number of branches which resulted into more number of pods per plant under these treatments. These improved yield parameters and yield in above treatments are resultant of better weed control which is indicated by perfect negative correlation between seed yield versus weed dry weights. The correlation analysis between weed data and seed yield stipulated that there was perfect negative correlation between weed dry weight at 50 DAS and weed dry weight at harvest and seed yield (-0.9928** and -0.9850**, respectively). In addition, regression equations explored that everyone g/m 2 increase in weed dry weight at 50 DAS and at harvest have reduced the seed yield of greengram by 7.85 and 9.89 kg/ha, respectively. Imazethapyr integrated with hand weeding at 30 DAS resulted in significantly higher seed yield over other treatments (Patel et al., 2016 b ) [25] . Jain et al. (2022) [14] also proved that the two years pooled mean data indicated that stale seedbed + hoeing once manually at 20 DAS + straw mulch (5 t/ha) at 30 DAS gave maximum grain yield of maize. Conversely, the unweeded check plot showed a significantly lower number of pods per plant and pod yield per plant, resulting in reduced overall seed and stover yields. This decline was due to the extensive and vigorous growth of weeds compared to all other weed control treatments due to no weed control action made. These findings are in agreement with those of Kushwah and Vyas (2006) [18] , Singh et al. (2010) [31] , Kundu et al. (2011 b ) [17] , Meena et al. (2011) [23] , Goud et al. (2014) [11] , Raut et al. (2018) [28] and Kumar and Hiremath. (2018) [16] . The data indicated that weed free treatment recorded lowest weed index. Further, imazethapyr 100 ml/ha as PoE at 15 DAS + interculture fb hand weeding at 40 DAS witnessed lower weed index which was followed by stale seedbed fb interculture and hand weeding at 40 DAS. Whereas, the highest weed index value was observed in the unweeded check. Wherein, imazethapyr 100 ml/ha as PoE at 15 DAS + interculture fb hand weeding at 40 DAS followed by stale seedbed fb interculture and hand weeding at 40 DAS witnessed lower weed index due to integration of different cultural, mechanical and chemical methods which effectively controlled different kinds of weeds and resulted in lower weed dry weight and ultimately higher weed control efficiency. Leva et al. (2018) [20] noticed lower weed index under imazethapyr 100 g/ha at 20 DAS + interculturing at 40 DAS which might be due to elimination of weeds by manual weeding and interculturing or by integration with herbicides. Mathukia et al. (2017) [22] also opined that weed free treatment recorded lowest weed index followed by hand weeding and interculturing and stale seedbed. The higher weed index in the unweeded check was attributed to the lower crop yield, which was a result of the significantly greater total dry weight of weeds. This increase in weed dry weight was due there was no weed control measure that ultimately resulting in poor yields in the unweeded check causing seed yield loss up to 68.22% in greengram. Similar findings were also reported by Mirjha et al. (2013) [24] , Godara et al. (2014) [10] , Datta et al.

(2017) [8] and Gelot et al. (2017) [9] .

Effect on quality parameters

The data indicated that different treatments tried in this experiment did not exert their significant impact on protein content. This was due to protein content of seed is essentially the manifestation of N content and as there was uniform application of nitrogen as the dose was common in all the treatments. The glimpse of data indicated that among different weed management practices protein yield was significantly higher under weed free treatment. Subsequently, significantly higher protein yield was registered with imazethapyr 100 ml/ha as PoE at 15 DAS + interculture fb hand weeding at 40 DAS which was statistically on par with stale seedbed fb interculture and hand weeding at 40 DAS. Wherein, unweeded check registered significantly lower protein yield. The higher protein yield recorded under above superior treatments was due to relatively higher seed yield reported under these treatments due to proper weed control. Hence, as the seed yield increased, protein yield was also increased and vice-versa. Hence, protein yield was direct reflection of seed yield in different treatments. Whereas, under unweeded check treatment protein yield was significantly lower because of lack of weed management practices which led to higher crop-weed competition resulting in poor yield resulting in lower protein yield. Treatment means with the letter(s) in common are not significant by DNMRT at 5% level of significance T1: Soil solarization fb castor shell mulch @ 7.5 t/ha at 10 DAS, T2: Soil solarization fb mustard straw mulch @ 5 t/ha at 10 DAS, T3: Soil solarization fb interculture and hand weeding at 40 DAS, T4: Stale seedbed fb castor shell mulch @ 7.5 t/ha at 10 DAS, T5: Stale seedbed fb mustard straw mulch @ 5 t/ha at 10 DAS, T6: Stale seedbed fb interculture and hand weeding at 40 DAS, T7: Imazethapyr 100 ml/ha as PoE at 15 DAS, T8: Imazethapyr 100 ml/ha as PoE at 15 DAS + interculture fb hand weeding at 40 DAS, T9: Weed free, T10: Unweeded check

Conclusion

Based on results of one year field experiment, it is concluded that either imazethapyr 100 ml/ha as PoE at 15 DAS + interculture fb hand weeding at 40 DAS or stale seedbed fb interculture and hand weeding at 40 DAS is suggested for effective control of weeds and achieving higher yield and net returns in kharif greengram.

Acknowledgement

AcknowledgementThe authors sincerely acknowledge the C. P. College of Agriculture, Sardarkrushinagar Dantiwada Agricultural University, Sardarkrushinagar for providing all the necessary facility for conducting of this experiment.

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