Maize is grown over more than193 Mha of land in 170 countries with a production of 1147.7 Mt and on a larger range of soil, biodiversity, climates and under different management systems (
Anonymous, 2020). In India, however, maize productivity is just half (2.96 t/ha) than the average productivity of the rest of the world. Broad-leaf weeds cause harm to crops in many ways and this happens due to the unusual adaptation characteristics of the weeds and their regeneration ability. Therefore, weed management is the major and important part of crop production. At present we have many selective herbicides with different modes of action of weed control in maize. 2, 4-D which kills broad leaved weeds after emergence by causing the cells in the tissues that carry water and nutrients to divide and grow without stopping. In view of this we conducted an experiment to find out the best dose of this herbicide for getting higher weed control efficiency and yields.
A field experiment was conducted during Rabi season of (2021) at AICRP Maize Agricultural Research Farm, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh. The soil was sandy clay loam, with pH 7.40, low in available organic carbon (0.41%), available nitrogen (207.47 kg/ha) and medium in available phosphorus (23.85 kg/ha) and potassium (219.60 kg/ha). The experiment was laid out in a randomized block design, comprising 7 treatments; weedy, two hand weedings at 20 and 40 DAS, 2, 4-D Sodium salt 80% WP 1250 g/ha at 25 DAS, 2, 4-D Sodium salt 80% WP 1000 g/ha, 2, 4-D Sodium salt 80% WP 750 g/ha and weed free replicated thrice. Maize variety ‘DHM-121’ was sown manually during the first week of December using the seed rate of 25 kg/ha and 60 cm×20 cm row-row and plant-plant spacing. Application of post-emergence herbicide was done according to the treatments using knap-sack sprayer fitted with flat-fan nozzle adopting a spray volume of 300 L/ha. Species-wise weed density and their biomass were measured at 45 DAS by placing a quadrate of 0.50 m
2 randomly at 2 places in each plot. Data on weed density and biomass were subjected to square root transformation before analysis. Biometric characters
viz. yield attributes and yields (grain and stover) of crop were recorded at harvest. The net return and benefit: cost ratio (BCR) were worked out on the basis of gross returns (Rs/ha) and cost of cultivation (Rs/ha). The differences within the treatment means were examined by means of “Critical Difference” (CD). Weed control efficiency was calculated by method of
Tripathi and Mishra, (1971) and weed index by
Gill and Kumar, (1969).
At 45 DAS, the weed density and dry weight were found lower in 2, 4-D Sodium salt 80% WP 1250 g/ha at 25 DAS in comparison to 2, 4-D Sodium salt 80% WP 1000 g/ha at 25 DAS and 2, 4-D Sodium salt 80% WP 750 g/ha at 25 DAS and these were recorded statistically similar with each other (Table 1). Study was supported by
Joshi et al., (2018) and
Mandi et al., (2019). The higher weed control efficiency and lower weed index were found in 2, 4-D Sodium salt 80% WP 1250 g/ha at 25 DAS over other doses of 2, 4-D. This might be due to more weed killing efficiency which resulted in lower weed dry matter accumulation. Study supported by
Triveni et al., (2017).
Visual phytotoxicity was observed at 1, 2, 5, 7 and 10 days after herbicide application based on scale where: 0=0%, 1, 1-10%; 2, 11-20%; 3, 21-30%; 4, 31-40%; 5, 41-50%; 6, 51-60%; 7, 61-70%; 8, 71-80%; 9, 81-90%; 10, 91-100% indicated that initially there were few phytotoxicity found in maize crop. The decreasing trends of phytotoxicity at various observations dates from 2 to 10 days from herbicide application revealed that with the advancement of the crop growth stages the visual symptoms of phytotoxicity disappeared. 2, 4-D Sodium salt 80% WP 2000 g/ha at 25 DAS showed higher phytotoxicity as compared to 2, 4-D Sodium salt 80% WP 1250 g/ha (Table 2).
Effect on rabi maize
Number of cobs per plant, number of grain rows per cobs and number of grains per row were found higher in 2, 4-D Sodium salt 80% WP 1250 g/ha at 25 DAS as compared to 2, 4-D Sodium salt 80% WP 1000 g/ha at 25 DAS and both were observed statistically at par with each other (Table 3). Higher grain and stover yields and seed index were obtained under 2, 4-D Sodium salt 80% WP 1250 g/ha at 25 DAS compared to 2, 4-D Sodium salt 80% WP 1000 g/ha at 25 DAS and 2, 4-D Sodium salt 80% WP750 g/ha at 25 DAS. This might be due to better yield parameters.
Economics
Amongst the different weed management treatments higher net return and B-C ratio were obtained in 2, 4-D Sodium salt 80% WP 1250 g/ha at 25 DAS than 2, 4-D Sodium salt 80% WP 1000 g/ha at 25 DAS. The possible reason behind it that higher economic yield.
