effect of weed management on weeds, nutrient uptake, nodulation, growth and yield of summer mungbean (Vigna radiata)

Abstract

1Department of Plant Breeding and Genetics. Mungbean [Vigna radiata (L.) Wilczek], also known as greengram, is the third most widely cultivated pulse crop in India. Pulse crops have been the mainstay of Indian agriculture for providing protein-rich diet to vegetarian masses of the country. Being leguminous crops they have beneficial effect on improving soil fertility through fixation of atmospheric nitrogen. Summer mungbean often suffers from severe crop-weed competition because it is grown under irrigated conditions. Infestation of weeds is a major constraint in achieving higher yield of summer mungbean (Singh and Sekhon, 2002), as these compete with crop plants for nutrients, moisture, light and space. The magnitude of reduction in yield depends upon the weed flora present, quantum of weed flora and duration of crop-weed competition. Critical period for crop-weed competition in summer mungbean is from 15 to 30 days after sowing (Singh et al., 1996). Thus, it is imperative to eliminate weeds from the crop at proper time and with suitable methods. Though weeds can be controlled by hoeing yet due to shortage of labour it becomes difficult to do hoeing at appropriate time and delayed hoeing may cause economic loss. A field experiment was conducted at the Punjab Agricultural University, Ludhiana, India during summer 2003 to study the effect of weed control in summer mungbean. Ludhiana (Latitude 30° 56′ N, longitude 75° 52′ E, altitude 247 m above the sea level) is located in the sub-tropical region. The soil of the experimental field was loamy sand in texture, having pH 8.2, low in organic carbon (0.33%), low in available nitrogen and medium in available phosphorus and potassium content. Twelve treatments viz., unweeded check, one and two hoeings [25 and 45 days after sowing (DAS)], two hoeings with wheel hoe (25 and 40 DAS), fluchloralin 0.625 kg/ha, trifluralin 0.96 kg/ha, pendimethalin 0.45 and 0.75 kg/ha, quizalofop-ethyl 35 and 50 g/ha and chlorimuron-ethyl 9 and 15 g/ha were tested in a randomized complete block design with four replications and net plot size was 4.5 x 2.025 m. The crop was sown on 28 March, 2003 in row spacing of 22.5 cm using a recommended seed rate of 37.5 kg/ha of variety SML 668. The pre-plant incorporation of fluchloralin and trifluralin and pre-emergence application of pendimethalin was done on the same day at the time of sowing and after sowing of the crop, respectively. The post-emergence application of quizalofop and chlorimuron was done 20 DAS using knapsack sprayer fitted with a flat-fan nozzle. Two hand hoeings were done at 25 and 40 days after sowing using khurpa (a small hand operated tool) and wheel hoe in respective treatments. Four irrigations were given to the crop : 1st on 13th April, 2nd on 23rd April, 3rd on 2nd May and 4th on 28th May. Data on weed count and weed dry matter were recorded 25 and 40 DAS and at harvest, using a quadrat measuring 50 x 50 cm. Data on nodulation and plant growth were recorded 25 DAS and data on yield and yield attributes were recorded at harvest. Weed as well as plant samples were analyzed for nutrient (nitrogen, phosphorus and potassium) uptake at harvest. The data were analyzed and treatments having a significant F value, critical difference (CD) values were calculated at 5% probability level.