ABSTRACT
Direct wet seeded-rice sown through drum seeder, a potential wise rice production system in the present-day scenario, is subject to severe weed infestation and, therefore, development of a sustainable weed management strategy is crucial for its wide spread adoption. The present study was conducted in kharif 2012 at department of agronomy division with NLR-33358 (SOMASILA) using six planting densities under five weed management conditions. The plant spacing tried were: 20cm x 7cm, 20 cm x 10.5 cm, 20 cm x 14 cm, 20 cm x 17.5 cm and 20 cm x 24.5cm and 20 cm x15cm. with a plant density of 71, 47, 35, 28, 20 and 33 hills m-2, respectively and five weed management practices viz., weedy check (W1), hand weeding at 20 and 40 DAS (W2), cono weeding at 20 and 40 with modified cono weeder (W3), pre-emergence application of anilofos @ 0.375 kg a.i ha-1 followed by post-emergence application of 2, 4 D sodium salt @ 1.0 kg a.i ha-1 20-25 DAS (W4), pre-emergence application of pendimethalin @1.0 kg a.i ha-1 followed by post-emergence application of bispyribac sodium @ 20 g a.i ha-1 30 DAS ( W5). . The experiment was laid out in strip- plot design with three replications assigning weed management techniques in vertical factor and plant spacing in horizontal factor. Direct wet seeded rice field was infested with 12 and 22 weed species, kharif -2012 season having Echinochloa colona, Leptochloa chinensis, Digitaria aescendens, Cyperus iriaand Eleusine indicaas the predominant weeds. Rice spacing exerted significant influence on both weed pressure and yield performance of crop. With the increase in plant spacing weed dry matter decreased but rice yield increased. In this season, among different plant densities, the highest density of 71 hills m-2(D1) resulted in minimum weed density, weed drymatter, and more number of tillers m-2 and maximum drymatter production at all stages of plant growth. closest spacing resulted in maximum weed suppression, but among various rice plant densities, a medium level population of 47 hills m-2 (D2) significantly increased the paddy yield over all other treatments except D1 treatments with a plant density of 71 hills m-2 .The highest grain yield of 3476 kg ha-1 was observed with a plant density of 47 hills m-2 and it was significantly superior to 71, 35, 28, 20 hills m-2drum seeded and 33 hills m-2 transplant paddies. which ultimately produced the highest rice yield. Weed inflicted relative yield loss was also minimized by the closest spacing. Present findings imply rice spacing mostly determines rice-weed competition, and can play a decisive role to minimize weed pressure. Therefore, closer spacing could be considered as a vital tool in the integrated weed management program for direct wet-seeded rice sown through drum seeder.
ABSTRACT
A field experiment was conducted to study the effect of top dressing of phosphorus through complex fertilizers on rice during kharif 2009 on clayey soil at Agricultural college farm Bapatla. Phosphorus uptake was significantly influenced due to sources of P at different times of application. Significantly higher P uptake in grain and straw was recorded with application of P as basal and at maximum tillering stages either through DAP or by 20:20:0 which was on a par with three splits of DAP and 20:20:0 and basal application of DAP, SSP and 20:20:0. The available P in soil was found significant among the treatments at 30 DAT, whereas, at 60 and 90 DAT and at maturity, it was non significant. The available nitrogen and potassium in soil after the harvest of rice crop was found non significant. Gross and net returns and benefit cost ratio were higher with application of P through DAP in two equal splits at basal and maximum tillering stages followed by 20:20:0; whereas, BCR was the highest with DAP in three splits.