Research Note J.Res. ANGRAU 39(1&2)60-63, 2011 INTEGRATED APPROACH FOR WEED CONTROL IN RABI GROUNDNUT (Arachis Hypogeae L) S. SRINIVASA RAO, M. MADHAVI and C. RAGHAVA REDDY Departmant of Agronomy, College of Agriculture, Acharya N G Ranga Agricultural University,Rajendranagar – 500030 Groundnut (Arachis hypogaea L.) is an important oil seed crop of Andhra Pradesh, which has low productivity and high cost of production. Area, production and productivity of groundnut during rabi in India were 6.41 Mha, 9.18 MT, and 1432 kg ha -1 during 2008, In AndraPradesh, the area, production, and productivity of groundnut were 2.64 Mha, 5.07 MT and 1921 kg ha -1 respectively (Department of Agriculture, AP, 2008-2009). Weed infestation is considered as one of the major factors in rabi groundnut production. Weed interference resulted in yield losses ranging between 74 and 92 percent (Agostinho et al., 2006). Critical period of crop weed competition for groundnut crop was reported to be upto 45 DAS and weed free environment during this period registered higher pod yield (Rao, 2000). Usually, in groundnut, weeds are controlled by physical methods and these cannot be used at all times and all stages of crop growth. Further, the labour availability for weeding is scarce and expensive. Use of pre and post emergence herbicides is the best alternative for weed control at critical periods. Combination of physical and chemical methods by use of post emergence herbicides like Imazethapyr or Quizalofop-p-ethyl (Bhatt et al., 2008) were suggested for controlling weeds effectively at later stages of crop growth and maintenance of weed free environment at critical stage of crop growth (Sailaja et al., 2002). Therefore field experiment was initiated to find out an effective and economical integrated weed management practice in rabi groundnut. Field experiment was conducted at College Farm, Rajendranagar of Acharya N.G. Ranga Agricultural University. The soil was sandy loam (Available N, P and K 252.9, 28.6 and 223 kg ha -1 respectively) with slightly alkaline reaction. The experiment was laid out in randomized block design with 12 treatments replicated thrice. The N, P 2 O 5 and K 2 O @ 30, 40 and 50 kg ha -1 were applied as basal through urea, single superphosphate and muriate of potash respectively. The groundnut cv. K 134 (Vemana) was sown at a spacing of 22.5 cm X 10 cm on 16 th November 2008. Pre emergence herbicide pendimethalin was applied on second day after sowing and post emergence herbicides were applied at 20 DAS. Weed flora of the experimental field consisted of grasses, sedges and broadleaved weeds. Among the weed control treatments, significantly lesser number of weeds were recorded at harvest in treatments of handweeding twice (T 2 ), Quizalofop-p-ethyl fb handweeding at 40 DAS (T 12 ), pendimethalin fb handweeding at 40 DAS (T 10 ), intercultivation with star weeder fb handweeding at 40 DAS (T 4 ) and imazethapyr fb handweeding at 40 DAS (T 11 ) (54 m -2 , 55 m -2 , 59 m -2 , 60 m -2 , 62 m -2 respectively). Pendimethalin fb imazethapyr (T 8 ) recorded higher weed density of 145 m -2 (Table 1). Unweeded check recorded highest total weed density (T 1 ) (353 m -2 ). Lower weed drymatter was obtained under T 2 , T 4 , T 10 , T 11 , T 12 and T 8 treatments (33, 35, 36, 38, 40 and 51 g m -2 respectively) and weed control efficiency (WCE) also exhibited the same trend (85.5%, 84.1%, 83.2%, 83.2%, 81.3% and 76.1%). The weed index was very low under treatments T 4 , T 8 , T 10 and T 11 due to application of pre-emergence herbicide which might have reduced the broad leaved weeds and certain grasses at early stage of crop growth (20 DAS). At 40 DAS, effective control of grasses, sedges and broad leaved weeds was noticed with hand weeding, intercultural operations and post emergence application of herbicides. Imazethapyr acts by inhibiting the enzyme (AHAS) activity and causes the disruption of protein synthesis and other subsequent bio-chemical reactions, which in turn inhibits the plant growth. These findings are in agreement with the results of Sasikala et al. (2002), Chandrika, (2004). Highest pod and haulm yields were email: cnu0294@gmail.com 60
INTEGRATED APPROACH FOR WEED CONTROL IN RABI GROUNDNUT 61