Effect of Integrated Weed Management Practices on Weed Parameters in Direct Seeded Aerobic Rice

Author: Kotresh D.J., S. Radhamani*, P. Murali Arthanari, V. Ravichandran, C. Bharathi and Sangothari A.

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Abstract

Weeds are the major constraints in aerobic rice cultivation, which offer stronger competition for essential growth factors. The weeds like Echinocloacolona and E. crus-galli affect the crop majorly. The yield loss may result in complete failure for crop. Even after development of several weed management strategies, no single method had proven fully effective. But the integrated approach that combines the advantages of various method can reduce the weed menace in aerobic rice cultivation. Different integrated weed management treatments were evaluated at Wetland farm, Department of Agronomy, TNAU, Coimbatore, to find the best performing integrated management practice during summer (March-July) 2022. Results showed that grassy weeds dominated in the aerobic rice field followed by broad leaved weeds. The integrated treatment, application of pyrazosulfuron ethyl (30g a.i./ha) as pre-emergence (3 DAS)fb bispyribac sodium (40g a.i./ha) as early post-emergence (12 DAS)fb one mechanical weeding (45 DAS) recorded higher weed control with decreased weed density (21.3/m2) and weed dry weight (15.55 g/m2)and the higher weed control efficiency (92.5%) at 60 DAS and was on par with the application of pendimethalin (1kg a.i./ha) as pre-emergence (3 DAS) fb two hand weeding (25 and 45 DAS).

Keywords

Aerobic rice, Bispyribac sodium, Pyrazosulfuron ethyl, Weed Control Efficiency, Weed Control index, Weed Persistence index

Conclusion

From the above results, it could be concluded that the treatment pyrazosulfuron ethyl (30g a.i./ha) as pre-emergence fb bispyribac sodium (40g a.i./ha) as early post-emergence fb one mechanical weeding (T6)gave broader spectrum control of weeds and reduced the weed density and weed dry matter and was comparable with the standard check of pendimethalin (1kg a.i./ha) as pre-emergence fb two hand weeding (T1), in terms of weed density and weed dry matter production.

References

INTRODUCTION Aerobic rice production is a newly evolved concept to get higher yields with less water. In comparison with cultivation of lowland transplanted rice, the aerobic rice saves nearly half of water by reducing the water requirements for land preparation and nursery raising and also due to absence of standing water. According to Castaneda et al., (2002), compared to lowland rice, water requirements in aerobic rice were 50per cent lower (470 mm—650 mm) and witnessed an increment of 64–88per cent in water productivity and a reduction in labor use by 55per cent. The reduction is also witnessed in seed rate, transplanting costs and labor wages (Kumar et al., 2020). In aerobic rice fields, the crop and weeds emerge together and weeds have comparative growth advantage. They compete for all the essential growth factors like light, space, nutrients and water. Weed competition is too severe that even within a single crop life cycle there may be three generations or flushes of weeds competing with them (Nagargade et al., 2018). The yield of aerobic rice will reduce to a greater extent if left un-weeded. The extent of loss in yields due to improper weed management ranges between 62.2 to 91.7 per cent (Sunil, 2018). The weed competition may rise up to the extent that rice crop will get killed and no grain yield can be obtained (Bhullar et al., 2016). This loss in yield can be overcome by efficient and integrated weed management practices. There are different methods of weed management, of which some are proven effective, some are economical and some others time saving. Hand weeding is the primitive method of weed management that stands best even today. Though hand weeding is considered as a standard, in direct-seeded aerobic rice it is time and labor consuming. Also, hand weeding is at least five times more cost intense than herbicides, especially under limited and expensive labour situations (Rao et al., 2017). Mechanical weeding helps in easy weeding than manual method, but it is confined to inter-row weeds, leaving the intra-row unattended. Singh et al. (2016) reported that in comparison with weed free condition, there was a reduction of 14-27 per cent rice grain yield in the plots treated with pendimethalin fb bispyribac sodium, which was due to the weeds that escaped herbicide applications, indicating the emerging ability of weeds even after chemical spray. Hence, studies have been made to evaluate the integrated approach of weed management. Munnoli et al. (2018) reported that higher growth and yield of aerobic rice in integrated weed management can be achieved by early control of initial flush of weeds by pre-emergence or early post-emergence and subsequent control of further weed growth by either manual or some herbicide application, that ensures necessary weed free conditions for better crop growth. Present study was taken up with different weed management methods like manual, mechanical and chemical methods, that are put together in different combinations and evaluated for efficient integrated weed management practice in aerobic rice. MATERIALS AND METHODS Field experiment was carriedout at Wetland Farms, Department of Agronomy, Tamil Nadu Agricultural University, Coimbatore during Summer (March-June) 2022. The soil of the experimental field was neutral in reaction (pH:7.7), low in available N (238.3 kg/ha) and medium in available P (12.1 kg/ha) and high in available K (408.7 kg/ha). The experiment was laid in randomised block design, with nine treatments replicated thrice. The treatment details are furnished in Table 1. The different herbicides used in the experimental study were pendimethalin, pyrazosulfuron ethyl and bispyribac-sodium. The mechanical weeding was carried out using rotary weeder. The treatment of pendimethalin with two hand weeding was taken as standard check for comparision of other integrated weed management treatments. Rice variety CO-53 was used in the experiment. The field was ploughed thoroughly and fine tilth was obtained to facilitate easy sowing. The gross plot size was 5m × 3m and net plot was 4.6m × 2.6m. Sowing was done manually on March second week with the seed rate of 75kg/ha, spacing of 20cm × 10cm and was irrigated immediately. Recommended dose of fertilisers (150:50:50 kg/ha of N, P and K) was given in split doses, along with basal micro-nutrient application of Zinc sulphate (25 kg/ha) and iron sulphate (25 kg/ha). The pre-emergence and early post-emergence herbicides were sprayed at 3 DAS and 12 DAS, respectively. Hand weeding and mechanical weeding operations were carried out as per the treatment schedule on 25 DAS and 45 DAS. Weed density and weed biomass of grasses and broadleaved weeds were recorded separately using 0.25m2 quadrat. The quadrat was placed in four random spots within each plot and weed count and weed biomass were taken for per square meter area. The observations were recorded at 30, 60 and 90 DAS. The weed samples were sun dried and oven dried for 24-48 hours at 65°C and weed dry matter was recorded. Weed control efficiency, weed control index and weed persistence index for all the treatments were calculated using the formula (Mani et al., 1973; Misra and Tosh, 1979; Mishra and Misra, 1997). Weed Control Efficiency = Weed Control Index = Weed Persistence Index = Where, WD = Weed density, WDM = Weed dry matter The weed data were statistically analysed according to the procedure given by Gomez and Gomez (1984) to find the significant difference (at five per cent probability level) and superior among the nine treatments. The data on weed density and weed dry matter is subjected to square root transformation (√(x+0.5)). RESULTS AND DISCUSSION Composition of weed flora in experimental field. Being sown in upland condition and receiving alternate wetting and drying method of irrigation, in the absence of standing water, aerobic rice recorded several species of weeds, that included mainly grasses and broadleaved weeds (Table 2). Weeds clearly showed periodicity of germination, as several weeds were seen after a month of sowing and few weeds made their presence even at flowering stage of crop. But the diversity of weed flora was restricted, as the experimental field was subjected to puddling in previous crop, which was also reasonable for absence of sedge weeds during entire period of crop growth (Munnoli et al., 2018). Weed density. Among the treatments, significant difference was recorded in weed densities in all the treated plots. At 30 DAS, the treatment application pendimethalin (1kg a.i./ha) as pre-emergence fb two hand weeding (T1) recorded significant superiority in controlling weed density (10.7/m2). This was on par with two hand weeding at 25th and 45th days (T7) (11.0/m2) andthe treatment of pyrazosulfuron ethyl (30ga.i./ha) as pre-emergence fb bispyribac sodium (40g a.i./ha) as early post-emergence fb one mechanical weeding (T6) (12.3/m2). The decreased weed density in these treatments indicated the efficient control of weeds with the pre-emergence application of pendimethalin and pyrazosulfuron ethyl at 3 DAS. Similar observations for pre-emergence application of herbicides were recorded by Awan et al. (2016); Singh et al. (2016). However, the control plot (T9) without any weed control measure recorded the highest weed density of 266.0/m2 (Table 3). The total weed density at 60 DAS was significantly reduced in the treatment, pendimethalin (1kg a.i./ha) as pre-emergence fb two hand weeding (T1) (20.3/m2), that was comparable with pyrazosulfuron ethyl (30g a.i./ha) as pre-emergence fb bispyribac sodium (40g a.i./ha) as early post-emergence fb one mechanical weeding (T6) (21.3/m2), while unweeded control plot (T9) recorded highest weed density (282.7/m2). The decreased weed density was attributed to the sequential application of pre-emergence and early post-emergence herbicides in the former treatment. Similar findings were also recorded by Hemalatha and Singh (2018); Kumar et al.(2020). At 90 DAS, the treatment of pendimethalin (1kg a.i./ha) as pre-emergence fb two hand weeding (T1) recorded significantly lower weed density (22.7/m2) and was followed by the application of pyrazosulfuron ethyl (30g a.i./ha) as pre-emergence fb bispyribac sodium (40g a.i./ha) as early post-emergence fb one mechanical weeding (T6) (23.0/m2) and application of early post-emergence bispyribac sodium (40g a.i./ha) fb one hand weeding (T4) (24.0/m2). The weed control with decreased weed densities reflected the benefit of integration of early post-emergence application of bispyribac sodium that either followed pre-emergence application of pyrazosulfuron ethyl or as alone fb one hand weeding (Rana et al., 2016; Patil et al., 2020; Kumari et al., 2016). The control of multiple flushes of weeds that germinate periodically was reason for better reduction in weed density. Weed dry matter. During early stage of crop growth, at 30 DAS, the treatments that combined the pre-emergence application of either pendimethalin (1kg a.i./ha) or pyrazosulfuron ethyl (30g a.i./ha) with hand weeding or early post-emergence spray of bispyribac sodium (40g a.i./ha)achieved significantly lower weed dry matter than other treatments. The weed dry matter in pendimethalin (1kg a.i./ha) applied as pre-emergence herbicide fb two hand weeding (T1) was 1.72g/m2, that was comparable with other two treatments, viz., pyrazosulfuron ethyl (30g a.i./ha) as pre-emergence that followed bispyribac sodium (40g a.i./ha) as early post-emergencefb one mechanical weeding (T6) (1.76 g/m2) and two hand weeding (T7) (1.80g/m2). The results were in accordance with Saravanane et al. (2016), where the pre-emergence herbicides have effectively controlled the initial flush of weeds by suppressing the germination and also by killing the emerging weeds. The treatment with pyrazosulfuron ethyl (30g a.i./ha) as pre-emergence fb bispyribac sodium (40g a.i./ha) as early post-emergence fb one mechanical weeding (T6) achieved significantly lower values for weed dry weight (15.55g/m2) at 60 DAS and was on par with pendimethalin (1kg a.i./ha) as pre-emergence fb two hand weeding (17.07g/m2) and bispyribac sodium (40g a.i./ha) as early post-emergence fb one hand weeding (T4) (17.81g/m2). The results were in accordance with Sar and Duary(2022). The highest weed dry weight was recorded in control plot (T9) without any treatment application (195.90g/m2). The weed dry weight reduction is clearly due to the efficient control of weeds by the application of early-post emergence bispyribac sodium(Kumar et al., 2013; Singh et al., 2016). The similar trend of observation was noticed at 90 DAS, where pyrazosulfuron ethyl (30g a.i./ha) as pre-emergence fb bispyribac sodium (40g a.i./ha) as early post-emergence fb one mechanical weeding (T6)recorded significantly lower values for weed dry weight (25.96g/m2). But the highest weed dry matter was seen in control (T9) (un-weeded check) (236.26g/m2). Weed control efficiency. Weed control efficiency varied between the treatments. Among the treatments, pendimethalin (1kg a.i./ha) as pre-emergence fb two hand weeding (T1) recorded highest per cent of weed control efficiency at 30, 60 and 90 DAS (96.0%, 92.8% and 91.3%, respectively). Similar recordings were also observed by Verma et al. (2017). The application of pyrazosulfuron ethyl (30g a.i./ha) as pre-emergence fb bispyribac sodium (40g a.i./ha) as early post-emergence fb one mechanical weeding (T6) was recorded the next best treatment at 60 and 90 DAS (92.5% and 91.2%, respectively). This indicated the broad-spectrum and longer period control of weeds by sequential application of herbicides and integrated management of weeds combined with mechanical weeding. Similar observation was also noted by Pinjari et al. (2016) and Soujanya et al. (2020). Two times hand weeded plots (T7)recorded better weed control efficiency at 30 DAS (95.9%), followed by the plots with sequential application of pyrazosulfuron ethyl, bispyribac sodium and mechanical weeding in order (T6) (95.5%). Weed control index. The weed control index was higher in the treatment of pyrazosulfuron ethyl (30g a.i./ha) as pre-emergence fb bispyribac sodium (40g a.i./ha) as early post-emergence fb one mechanical weeding (T6), at 30, 60 and 90 DAS with values of 95.8, 92.1 and 89.0, respectively. This was followed by the treatment, pendimethalin (1kg a.i./ha) as pre-emergence fb two hand weeding (T1) (95.9, 91.3 and 87.8, respectively). With these values, it was clear that the treatment of sequential application of herbicides with mechanical weeding had reduced the weed dry weight efficiently over the control plots (un-weeded check) Singh et al.(2018) also recorded similar observations. Among the treatments, two times mechanically weeded plots (T8) recorded very low weed control index at all the observations. Weed persistence index. Weed persistence index is a measure of persistence/resistance of the weeds that escaped the applied treatment, whose higher value indicates greater persistence and lower indicating less (Garko et al., 2020).The treatment of pyrazosulfuron ethyl (30g a.i./ha) as pre-emergence fb bispyribac sodium (40g a.i./ha) as early post-emergence fb one mechanical weeding (T6) had recorded lowest weed persistence values at 30 and 60 DAS (0.91 and 1.06, respectively) and at 90 DAS, the value was 1.25, which was similar to two hand weeding treatment. This indicated the lower persistence of weeds in these treatments. The results were in line with Mishra et al.(2016).

How to cite this article

Kotresh D.J., S. Radhamani, P. Murali Arthanari, V. Ravichandran, C. Bharathi and Sangothari A. (2022). Effect of Integrated Weed Management Practices on Weed Parameters in Direct Seeded Aerobic Rice. Biological Forum – An International Journal, 14(2a): 539-544.