Effect of pre and post-emergence herbicide combinations on weed dynamics and yield of Rabi maize (Zea mays L.)

Introduction

Maize (Zea mays L.) is one of the most important cereal crops worldwide and is popularly known as the "Queen of Cereals" because of its high yield potential, wide adaptability, and diverse uses as food, feed, fodder, and industrial raw material. It ranks third among cereal crops after rice and wheat in terms of global production and economic importance (Parihar et al., 2011) [10] . As a C4 plant, maize possesses high photosynthetic efficiency and superior water-use efficiency, enabling it to perform well under a wide range of agro-climatic conditions, particularly in tropical and subtropical regions. The crop was domesticated approximately 9,000 years ago in Southern Mexico and Mesoamerica (Awika, 2011) [1] and has since become a staple food and an important source of income for millions of farmers across the world. In India, maize is cultivated over an area of 12.02 million hectares with an annual production of 42.28 million tonnes. Rajasthan is one of the major maize-growing states, accounting for about 1.01 million hectares with a production of 2.67 million tonnes (UPAg, 2024-25). In recent years, rabi maize cultivation under irrigated conditions has expanded considerably owing to its higher productivity, better grain quality, and increasing demand from the feed, food processing, and starch industries. Despite its high genetic yield potential, maize productivity is often limited by severe weed infestation, particularly during the early stages of crop growth. Weeds are considered one of the most important biotic constraints as they compete aggressively with the crop for nutrients, soil moisture, light, space, and other essential growth resources. The critical period of crop-weed competition in maize generally occurs during the first 30-45 days after sowing, during which uncontrolled weed growth can substantially reduce crop growth and yield. Yield losses due to weed competition have been reported to range from 28 to 100%, depending on weed flora, infestation level, environmental conditions, and management practices (Patel et al., 2006) [12] . In many situations, losses caused by weeds exceed those resulting from insect pests and diseases combined (Kumar et al., 2019) [9] . In addition to direct competition, certain weed species release allelopathic compounds that suppress seed germination, retard crop growth, and adversely affect grain yield and quality. Timely and effective weed management is therefore essential for realizing the full yield potential of maize. Although manual and mechanical weeding are effective, their adoption is often constrained by labour scarcity, increased wages, and the narrow window available for timely operations. Consequently, chemical weed management has emerged as an efficient, economical, and practical alternative for large-scale maize cultivation. The use of pre-emergence (PE) herbicides provides effective control of weeds during the initial stages of crop establishment, whereas post-emergence (PoE) herbicides help manage weeds that emerge later in the growing season. Sequential application of pre-and post-emergence herbicides offers broader-spectrum weed control and improves management of grassy weeds, sedges, and broadleaved weeds compared with the application of a single herbicide (Triveni et al., 2017) [19] . Previous studies have demonstrated that effective weed control through appropriate herbicide use can enhance maize grain yield by 77-96.7% over untreated weedy conditions (Khan et al., 1998) [8] . Therefore, identifying suitable herbicide combinations and their optimum application timing is essential for sustainable weed management, improved crop productivity, and enhanced profitability in maize cultivation.

Materials and Methods

The field experiment was conducted at Field No. 10, Agricultural Research Station, Banswara, Rajasthan, during the rabi season of 2025-26 to evaluate the efficacy of sequential herbicide applications for weed management in maize. The experiment was laid out in a Randomized Block Design (RBD) comprising 12 treatments with three replications. The treatments consisted of: T₁ -weedy check; T₂ -weed-free; T₃ -atrazine @ 500 g ha⁻¹ + hand weeding at 25 DAS; T₄pyroxasulfone @ 127 g ha⁻¹ + hand weeding at 25 DAS; T₅atrazine @ 500 g ha⁻¹ followed by (fb) halosulfuron-methyl @ 67 g ha⁻¹ at 25 DAS; T₆ -atrazine @ 500 g ha⁻¹ fb tembotrione @ 120 g ha⁻¹ at 25 DAS; T₇ -atrazine @ 500 g ha⁻¹ fb topramezone @ 25 g ha⁻¹ at 25 DAS; T₈ -atrazine @ 500 g ha⁻¹ fb mesotrione + atrazine @ 300 g ha⁻¹ at 25 DAS; T₉ -pyroxasulfone @ 127 g ha⁻¹ fb halosulfuron-methyl @ 67 g ha⁻¹ at 25 DAS; T₁₀pyroxasulfone @ 127 g ha⁻¹ fb tembotrione @ 120 g ha⁻¹ at 25 DAS; T₁₁ -pyroxasulfone @ 127 g ha⁻¹ fb topramezone @ 25 g ha⁻¹ at 25 DAS; and T₁₂ -pyroxasulfone @ 127 g ha⁻¹ fb mesotrione + atrazine @ 300 g ha⁻¹ at 25 DAS. The maize hybrid Bio-9782 was sown during the second week of November 2025 at a spacing of 60 cm × 20 cm. Recommended agronomic practices were followed uniformly for all treatments throughout the crop growth period. Pre-emergence herbicides (atrazine and pyroxasulfone) were applied two days after sowing, while post-emergence herbicides were sprayed 25 days after sowing (DAS) using a knapsack sprayer fitted with a flat-fan nozzle. Weed observations were recorded at 50 DAS using a 0.5 m × 0.5 m quadrat placed randomly at two locations within each plot. Weed density was recorded separately for grassy weeds, sedges, and broad-leaved weeds and expressed as number m⁻². For determination of weed dry matter, weeds within the quadrat were uprooted, washed to remove adhering soil particles, shade-dried for 24 h, and subsequently oven-dried at 65 °C until a constant weight was attained. The dry weight was expressed as g m⁻². To normalize the distribution of weed count data, observations were subjected to square-root transformation using the formula √(X + 0.5) before statistical analysis. Weed control efficiency (WCE) was calculated based on total weed dry matter using the standard. The crop was harvested manually during the middle of March 2026. Grain and stover yields were recorded on a plot basis and converted to kg ha⁻¹. The experimental data were subjected to analysis of variance (ANOVA) appropriate for the Randomized Block Design, and treatment means were compared using the least significant difference (LSD) test at the 5% probability level.

Results and Discussion

Weed density

The experimental field was infested with mixed population of grassy weeds, sedges and broad-leaved weeds, with dominance of grassy weeds. The total weed density was computed by summing the population of grassy weeds, sedges and broad-leaved weeds. Data presented in Table 1 revealed that different weed management practices significantly reduced the density of grassy weeds as compared to weedy check. The maximum grassy weed density was recorded under weedy check (T1) with 13.86 m -2 , whereas the minimum was observed under pyroxasulfone @ 127 g ha -1 fb tembotrione @ 120 g ha -1 (T10) with 2.51 m -2 , which was statistically at par with pyroxasulfone @ 127 g ha -1 fb topramezone @ 25 g ha -1 (T11) (2.64 m -2 ) and pyroxasulfone @ 127 g ha -1 fb halosulfuron methyl @ 67 g ha -1 (T9) (2.67 m -2 ). The reduction in grassy weed density under T10 was about 81.89 per cent over weedy check. This might be due to effective pre and post-emergence herbicidal action which suppressed early as well as later flushes of weeds, as also reported by Sepat and Singh (2024) [14] . In case of sedges, the highest density was recorded under weedy check (6.52 m -2 ), whereas the lowest density was observed under T9 (1.95 m -2 ), which was statistically at par with T12 (2.20 m -2 ) and T5 (2.24 m -2 ). However, treatments involving hand weeding viz., T3 (6.02 m -2 ) and T4 (5.47 m -2 ) recorded comparatively higher sedge density. This might be attributed to the regeneration ability of sedges through underground propagules, which proliferate when soil is disturbed, as also reported by Thakur (2022) [17] . The density of broad-leaved weeds was also significantly influenced by different treatments. The maximum population was recorded under weedy check (7.74 m - 2 ), whereas the minimum was observed under T10 (4.26 m -2 ), which was statistically at par with T6 (4.32 m -2 ) and T11 (4.62 m - 2 ). These results are in agreement with the findings of Sundari et al. (2019) [15] , who also reported effective control of dicot weeds with sequential herbicide application. Total weed density was significantly reduced under all weed control treatments compared to weedy check (17.14 m -2 ). Among the treatments, pyroxasulfone @ 127 g ha -1 fb tembotrione @ 120 g ha -1 (T10) recorded the lowest total weed density (5.89 m -2 ), which was statistically at par with T11 (6.24 m -2 ) and T9 (6.18 m -2 ), and proved superior over rest of the treatments. The reduction in total weed density under T10 was about 65.64 per cent over weedy check. This might be due to the fact that pre-emergence application of pyroxasulfone restricted weed germination by inhibiting very long chain fatty acid synthesis, while postemergence application of tembotrione inhibited HPPD enzyme, leading to bleaching and death of weeds (Hardwick, 2013) [7] .

Yield

The data presented in Table 2 revealed that grain and stover yield of the crop were significantly influenced by different weed management practices. Among the treatments, the highest grain yield was recorded under T₂ (6641 kg ha -1 ), which was statistically at par with T₁₀ (6610 kg ha -1 ) and T₁₁ (6408 kg ha -1 ). The lowest grain yield was observed under weedy check (T₁) (3543 kg ha -1 ). The increase in grain yield under T₂ was about 87.46 per cent over weedy check. This increase in yield might be attributed to effective weed control which reduced crop-weed competition for nutrients, moisture and light, thereby enhancing crop growth and productivity. Similarly, stover yield was also significantly affected by different treatments. The maximum stover yield was recorded under T₂ (9569 kg ha -1 ), which was closely followed by T₁₀ (9338 kg ha -1 ) and T₁₁ (9175 kg ha -1 ), whereas the minimum was recorded under weedy check (T₁) (4543 kg ha -1 ). The higher stover yield under these treatments might be due to better vegetative growth as a result of reduced weed competition throughout the crop growth period. Overall, treatments involving effective weed management practices resulted in higher grain and stover yield as compared to other treatments. This might be due to season-long weed control which ensured better availability of resources to the crop. -1 fb hand weeding at 25 DAS 5264 8298 T4: Pyroxasulfone @ 127 g ha -1 fb hand weeding at 25 DAS 5343 8009 T5: Atrazine 500 g ha -1 fb halosulfuron methyl @ 67 g ha -1 at 25 DAS 5240 8207 T6: Atrazine 500 g ha -1 fb tembotrione @ 120 g ha -1 at 25 DAS 5432 8632 T7: Atrazine 500 g ha -1 fb topramezone @ 25 g ha -1 at 25 DAS 5230 8130 T8: Atrazine 500 g ha -1 fb mesotrione + atrazine @ 300 g ha -1 at 25 DAS 6005 8125 T9: Pyroxasulfone @ 127 g ha -1 fb halosulfuron methyl @ 67 g ha -1 at 25 DAS 5843 7993 T10: Pyroxasulfone @ 127 g ha -1 fb tembotrione @ 120 g ha -1 at 25 DAS 6610 9338 T11: Pyroxasulfone @ 127 g ha -1 fb topramezone @ 25 g ha -1 at 25 DAS 6408 9175 T12: Pyroxasulfone @ 127 g ha -1 fb mesotrione + atrazine @ 300 g ha -

Conclusion

The findings of the present study demonstrated that sequential herbicide application was more effective than single herbicide application in managing the diverse weed flora of maize. Among the treatments evaluated, the application of pyroxasulfone @ 127 g ha⁻¹ as a pre-emergence herbicide followed by (fb) tembotrione @ 120 g ha⁻¹ at 25 DAS as a post-emergence herbicide proved to be the most effective, resulting in superior weed control efficiency and significantly higher grain and stover yields. The performance of this treatment was comparable to the weed-free treatment, indicating its effectiveness in suppressing grassy, broad-leaved, and sedge weeds throughout the critical crop growth period. Therefore, this sequential herbicide application can be recommended as an efficient and economical weed management strategy for rabi maize cultivation, particularly under conditions of labour scarcity and rising labour costs. Its adoption has the potential to improve maize productivity while ensuring timely and effective weed control.

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