MSc

ABSTRACT


A field experiment on “Weed management in summer groundnut (Arachis hypogaea L.)” was undertaken during 2018-20 with the objectives to find out the best weed management option for the summer groundnut in the Onattukara tract and to work out the economics of cultivation. The experiment was carried out from December 2019 to April 2020 in farmer’s field at Vallikunnam Panchayath in the Onattukara region of Alappuzha district.
The experiment was laid out in randomized block design with 9 treatments replicated thrice. The treatments were T1 - stale seed bed fb 1 hand weeding at 30 DAS; T2 - imazethapyr + imazamox (PoE) @ 40 g ha-1 at 20 DAS; T3 - imazethapyr + imazamox (PoE) @ 80 g ha-1 at 20 DAS; T4 - imazethapyr (PoE) @ 37.5 g ha-1 at 20 DAS; T5 - imazethapyr (PoE) @ 70 g ha-1 at 20 DAS; T6 - pendimethalin (PE) @ 1.0 kg ha-1; T7 - pendimethalin (PE) @ 1.0 kg ha-1 fb hand weeding at 30 DAS; T8 – hand weeding at 20 DAS and 45 DAS; T9 – unweeded check. FYM @ 2 t ha-1, N: P2O5: K2O
@ 10:75:75 kg ha-1 (as basal) and lime 1.5 t ha-1 (at flowering) were applied uniformly to all treatments. The bunch type groundnut variety, CO7 was sown at a spacing of 15 cm x 15 cm.
The growth characters, viz., plant height, number of branches and leaf area were recorded at 30, 45, 60 DAS and at harvest. The plant height was higher in T5 at all growth stages except at 30 DAS. Number of branches was higher in T5 which was on par with T1 at all growth stages. The leaf area per plant was higher in T3 and T5 at 60 DAS and at harvest. Higher 100 kernel weight was observed in T5 (48.3 g) which was on par with T1, T3, T4 and T7. The number of pods per plant was higher for T5 (43.2) which was on par with T3 and T7. The treatment T5 recorded higher kernel yield (1652 kg ha-1) and haulm yield (3502 kg ha-1) and was on par with T8, T1 and T3 for kernel yield and with all treatments except T2 and T9 for haulm yield. Harvest index of T5 (0.393) was on par with all treatments except T2 and T9. The shelling percentage was recorded higher in T5 (72.95) which was on par with T4, T2, T7, T1 and T8.



The predominant weed flora of the experimental field was broadleaved weeds followed by grasses and sedge. Lower weed density and dry weight at early stage were recorded in pre emergence application treatments (T6 and T7). At 30 DAS, treatments T8, T7, T5 and at 45 DAS, T1, T5 and T7, respectively recorded lower weed density and dry weight. Nutrient removal by weeds at flowering was also influenced by the treatments. The WCE was the highest in T7 (91.41%) at 15 DAS, T8 (40.96%) and T5 (37.91%) at 30 DAS and T1 (70.95%) and T5 (68.44%) at 45 DAS. Negative value of weed index in T5 (-
9.94 %) indicated the superiority of T5 over hand weeding treatment (T8).

Plant N, P, K uptake was higher in T5 (post-emergence application of imazethapyr
@ 70 g ha-1 at 20 DAS). The chemical properties of soil were not influenced by the treatments except available nitrogen content which was recorded higher in T8 and was on par with T1, T4, T6, T7 and T9. No serious pest and diseases were observed during the study. T5 recorded the highest net income and B-C ratio (₹ 95611 and 2.46, respectively). It was followed by T3 which recorded a BCR of 2.12.
The results of the study revealed that post-emergence application of imazethapyr
@ 70 g ha-1 at 20 DAS (T5) is the effective weed management practice for summer groundnut in Onattukara considering the growth, yield and economics.