Residual effect of wheat herbicides on establishment, growth and yield of succeeding summer greengram

Introduction

In India, cereal-pulse cropping systems heavily rely on wheat (Triticum aestivum L.), a significant cereal crop. Summer greengram (Vigna radiata L.) is an important short-duration pulse crop that can be successfully grown after wheat and contributes to soil fertility through biological nitrogen fixation. The wheat-greengram cropping sequence is therefore an important option for improving land use efficiency, farm productivity and sustainability. Weeds are one of the major constraints to wheat production and can cause considerable losses in crop growth and yield. Herbicides are widely used for effective and timely weed management in wheat, particularly where manual weeding is costly and labour availability is limited (Singh et al., 2012; Yadav et al., 2019) [4,6] . However, the use of herbicides in one crop may result in residues persisting in the soil and may influence the establishment and growth of the succeeding crop. Herbicide characteristics, application rate, soil pH, moisture, temperature, and microbial degradation are some of the variables that affect herbicide carry-over and persistence. While certain popular herbicides have been shown to be safe for greengram and other rotating crops, previous research has also demonstrated that some herbicides applied to wheat may produce residual harm to subsequent crops. (Yadav et al., 2004; Zahan et al., 2018) [5,8] . Therefore, evaluation of the residual effect of used herbicide treatments in wheat is important for ensuring the safe establishment and productivity of the succeeding summer greengram crop. The present study was undertaken to assess the residual effects of herbicides applied in preceding wheat on the growth and yield of succeeding summer greengram under the prevailing agro-ecological conditions.

Materials and Methods

A field experiment was conducted during the summer seasons of 2024-25 and 2025-26 to evaluate the residual effect of herbicides applied in the preceding wheat crop on succeeding summer greengram. The experiment comprised nine treatments, including different herbicides applied in wheat, hand weeding and a weedy check. The herbicide treatments included pyroxasulfone, pinoxaden, metsulfuron methyl, clodinafop-propargyl, clodinafop-propargyl + metribuzin, 2,4-D + carfentrazone and clodinafop-propargyl + metsulfuron methyl. Hand weeding and weedy check were maintained as comparative treatments. After harvesting the wheat crop, summer greengram was sown in the same plots without disturbing the soil. The recommended dose of fertilizers and other agronomic practices were followed uniformly for all treatments. Observations on plant population, plant height, chlorophyll content, yield attributes and seed yield were recorded at different growth stages of greengram. Plant population was recorded at 15 days after sowing and at harvest, while plant height and chlorophyll content were measured at 40, 60 days after sowing and at harvest. The residual effect of the herbicides was assessed by comparing the growth and yield performance of greengram under different preceding wheat herbicide treatments. The data were statistically analysed using analysis of variance for randomized block design. Treatment means were compared using the critical difference at the 5% level of significance.

Results and Discussion

Plant Population

The data on plant population of succeeding summer greengram at 15 DAS and at harvest are presented in Table 1. Plant population did not differ significantly among the treatments during either year of experimentation. At 15 DAS, the mean plant population ranged from 108.92 to 113.04 plants m -2 . Numerically, the highest population was recorded under hand weeding (T 8 ) with 113.04 plants m -2 , followed by clodinafop-propargyl + metsulfuronmethyl (T 7 ) with 112.72 plants m -2 , whereas the lowest population was observed under the weedy check (T 9 ) with 108.92 plants m -2 . A similar trend was observed at harvest, where plant population ranged from 108.00 to 111.52 plants m -2 . The absence of significant differences indicates that the herbicides applied in the preceding wheat crop did not adversely affect the establishment or survival of succeeding greengram. Similar findings were reported by Yadav et al. (2004) [5] , who observed no adverse carry-over effect of several wheat applied herbicides on succeeding greengram. Zahan et al. (2018) [8] and Shamim et al. (2020) [3] also reported that herbicide residues from wheat did not adversely affect the establishment of succeeding greengram. Hossain et al. (2022) [1] further reported that different herbicide treatments had no significant effect on greengram plant population, root and shoot growth, biomass, seed yield or seed germination.

Plant Height

Plant height of succeeding summer greengram was recorded at 40 DAS, 60 DAS and at harvest (Table 2). The effect of herbicide treatments applied to the preceding wheat crop was nonsignificant at all stages of observation. At 40 DAS, mean plant height ranged from 14.07 cm weedy check (T 9 ) to 17.57 cm under clodinafop-propargyl + metsulfuron-methyl (T 7 ). At 60 DAS, the maximum numerical height was recorded under hand weeding (T 8 ) with 26.70 cm, followed by clodinafop-propargyl + metsulfuron-methyl (T 7 ) with 26.33 cm. At harvest, hand weeding (T 8 ) recorded the highest numerical plant height of 41.41 cm, followed by clodinafop-propargyl + metsulfuron-methyl (T 7 ) with 41.14 cm, whereas the lowest value was recorded under the weedy check (T 9 ) with 28.87 cm. Since the differences were statistically non-significant, the observed variation should be considered numerical rather than a residual phytotoxic response greengram. These findings are in agreement with Yadav et al.

(2019) [6] , who reported that herbicides applied in wheat did not show residual toxicity on the plant height of succeeding. Jain et al. (2020) [2] , who reported no harmful residual effect of wheat herbicides on succeeding greengram. Similarly, Yadav et al.

(2021) [7] reported that herbicide mixtures applied in wheat did not show residual toxicity on succeeding greengram and other predominant legume crops grown after wheat. Yadav et al. (2019) [6] also reported that herbicides and herbicide mixtures used in wheat did not adversely influence the performance of succeeding crops.

Chlorophyll Content

Chlorophyll content of succeeding summer greengram was not significantly affected by the herbicide treatments applied in the preceding wheat crop (Table 3). The mean values ranged from 39.33 to 46.07. Numerically, the highest chlorophyll content was recorded under hand weeding (T 8 ) with 46.07, followed by clodinafop-propargyl + metsulfuron-methyl (T 7 ) with 45.70, while the lowest value was recorded under the weedy check (T 9 ) with 39.33. The higher numerical chlorophyll content under T 7 and T 8 was consistent with their comparatively better plant growth. However, the differences were statistically nonsignificant, indicating that the tested herbicides did not cause appreciable residual toxicity affecting the chlorophyll status of succeeding greengram. Similar observations were reported by Zahan et al. (2018) [8] , who found that chlorophyll content and dry matter of succeeding greengram were not adversely affected by residues of herbicides applied in wheat. Shamim et al. (2020) [3] also reported no adverse effect of wheat applied herbicide residues on greengram growth and chlorophyll content.

Seed Yield

Seed yield of succeeding summer greengram was not significantly influenced by the herbicide treatments applied to the preceding wheat crop (Table 4). The mean yield ranged from 833 to 1136 kg ha ha -1 . The highest numerical seed yield was recorded under clodinafop-propargyl + metsulfuron-methyl (T 7 ) with 1136 kg ha ha -1 , followed by hand weeding (T 8 ) with 1130 kg ha ha -1 , while the lowest yield was recorded under the weedy check (T 9 ) with 833 kg ha ha -1 . The better numerical performance under T 7 and T 8 was associated with comparatively better crop growth, whereas the lower yield under the weedy check may be related to greater weed interference in the preceding cropping system. However, as the treatment effect was non-significant, these numerical differences cannot be attributed to a significant residual effect of the herbicides. Yadav et al. (2019) [6] similarly reported that herbicides applied in wheat did not produce residual toxicity in succeeding greengram. Earlier, Yadav et al. (2004) [5] also reported that several herbicides used in wheat did not adversely affect succeeding greengram. Yadav et al. (2021) [7] also observed no residual toxicity of herbicides and herbicide mixtures applied in wheat on succeeding legume crops, including mungbean.

Conclusion

The study revealed that the herbicides applied in the preceding wheat crop had no significant residual effect on the establishment, growth, chlorophyll content and seed yield of succeeding summer greengram. Plant population, plant height and chlorophyll content remained statistically comparable among the treatments. Although numerical differences were observed, clodinafoppropargyl + metsulfuron-methyl (T 7 ) and hand weeding (T 8 )

generally recorded better crop performance, while the weedy check (T 9 ) showed comparatively lower values. The highest numerical seed yield was recorded under T 7 (1136 kg ha -1 ), followed by T 8 (1130 kg ha -1 ), whereas the lowest was observed under T 9 (833 kg ha -1 ). Overall, the findings indicate that the tested wheat herbicide treatments did not cause measurable residual phytotoxicity to succeeding summer greengram under the conditions of the study.

References

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