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  • ThesisItemOpen Access
    Productivity of semi-dry rice under simultaneous in situ green manuring
    (Department of Agronomy, College of Horticulture, Vellanikkara, 1995) Musthafa, Kunnathadi; KAU; Neelekantan Potty, N
    An investigation aimed to study the influence of simultaneous in situ green manuring on the growth, yield and nutritional characteristics of rice was conducted during the first crop season of 1993 – 94 in the sandy clay loam soils of the Agricultural Research Station, Mannuthy. The treatments consisted of factorial combinations of four levels of nitrogen (0,35,70 and 105 kg N ha-1), two levels of phosphorus ( 0 and 35 kg P2O5 ha-1) and two seed rates of cowpea (15 and 30 kg ha-1) for in situ green manuring and a control without green manure. Cowpea was raised in alternate rows of rice. The experiment was laid out in RBD with three replications. Results of the study showed that simultaneous in situ raising of cowpea for green manure can be successfully practiced in semi-dry rice for improving the productivity. At the recommended level of fertilizers (70:35:35 kg N, P2O5, K2 O ha-1) a lower seed rate of cowpea was found to be the best which gave 24 and 64 per cent more yield of grain and straw, respectively than the recommended practice. However, a higher seed rate of cowpea was required if the level of N was limited to 35 kg ha-1. The system added 58 and 76 q of green matter ha-1 at the lower and higher seed rates, respectively. The system effectively minimised the production and decline of non productive tillers in the post flowering phase and contributed to the increased yield. The increased efficiency of plant N achieved in the system appeared to arise from a widening of N/Fe ratio as well as a regulatory influence on elements in the plant system. Intercropping of cowpea for green manure increased the incidence of leaf roller and sheath blight marginally. The system also suppressed the weed growth in the cropped field and the weed biomass production declined by 45 per cent by 20 DAS. Weeds removed larger quantities of K and Mg than rice and deplete the soil of these nutrients. Intercropping effectively checked this. The suppression effect was not uniform on all types of weeds. Sedges showed a tendency to increase when broad leaved weeds declined. Grassy weeds remained unaffected. Thus simultaneous in situ green manuring appears to change the weed spectrum in rice fields. A comparative analysis of the weather pattern during the season with that of the normal showed that the system can be successfully adopted in similar areas.
  • ThesisItemOpen Access
    Integrated weed management under system of rice intensification (SRI)
    (Department of Agronomy, College of Horticulture, Vellanikkara, 2011) Musthafa, Kunnathadi; KAU; Abraham, C T
    An experiment was conducted to assess the performance of system of rice intensification (SRI) vis-à-vis conventional system with special emphasis on weed problems under SRI and to develop an economic weed management strategy. Aiming at reducing drudgery while using manual cono weeder, it was also envisaged to develop the prototype of a self propelled cono weeder. The field studies laid out in randomized block design with 16 treatments in three replications were conducted at RARS, Pattambi in Palakkad district and in farmers’ fields at Alappad Kole in Thrissur district, during the Mundakan seasons of 2007 and 2008. The soil at Pattambi was lateritic sandy clay loam with pH 4.96 and medium fertility, and that at Alappad Kole was clayey in texture with pH 5.0 and of high fertility. At both locations, the density and dry weight of weeds at 45 and 60 days after transplanting (DAT) were higher in all the SRI treatments especially when weed control was done through repeated cono weeding. At Pattambi, weed density and weed dry weight were the lowest in conventional system with post emergence herbicides, which recorded lower nutrient removal by the weeds and the lowest weed index and also higher gross return, net return and B:C ratio. The weed density and dry weight in the SRI fields were the lowest with pre emergence herbicide followed by hand weeding at 30 DAT, but the use of post emergence herbicides showed higher B:C ratio. At Alappad Kole, the weed density and dry weight, both at 45 and 60 DAT, were the lowest in conventional system with cono weeding at 10 DAT followed by post emergence herbicides. Cono weeding followed by hand weeding, pre emergence herbicides followed by hand weeding as well as the use of post emergence herbicides were also equally effective in controlling the weeds 233 in the conventional system, and were on par in the B:C ratios. In the SRI plots cono weeding at 10 DAT followed by post emergence herbicides recorded the lowest weed density and dry weight, however, use of post emergence herbicides recorded the highest net return and B:C ratio among the SRI treatments. Thus, considering the acute shortage and high wages for the labourers in Kerala, weed management through post emergence herbicides will be the preferable option for the farmers in both conventional and SRI systems of rice cultivation. Comparison between the two systems of rice cultivation at two different rice growing ecosystems showed that SRI improved the performance of individual hills through higher number of tillers hill-1, root length and root dry weight hill-1. On the other hand, the tiller number, dry matter production, root dry weight and productive tillers per unit area were higher in the conventional treatments. Owing to higher number of productive tillers per unit area the grain yield of conventional treatments was significantly higher than that of the typical SRI. At Pattambi, conventional system with post emergence herbicides recorded higher number of productive tillers m-2, panicle length, number of filled grains panicle-1, 1000 grain weight and grain yield (2877 kg ha-1), which was 33 per cent higher than the grain yield in the typical SRI. This treatment also recorded significantly higher B:C ratio (1.27) compared to that (0.91) of the typical SRI. However, the highest straw yield (2510 kg ha-1) at Pattambi was observed in ‘SRI with cono weeding at 10 DAT followed by post emergence herbicides’, which was on par with the typical SRI treatment. At Alappad Kole, higher number of productive tillers m-2, more filled grain percentage, highest 1000 grain weight, highest grain yield (6073 kg ha-1) and highest straw yield (5109 kg ha-1) were recorded by conventional system with cono weeding followed by hand weeding, which showed an increase of 93 per 234 cent in grain yield, with an additional yield of 2934 kg ha-1, and 109 per cent in straw yield over the typical SRI and recorded the highest gross return, net return and B:C ratio (2.46). Thus, the study showed the superiority of conventional system of rice cultivation at a spacing of 20 cm x 10 cm over the SRI system at a spacing of 30 cm x 30 cm at both the two different rice growing ecosystems studied viz., the sandy loam soils at Pattambi and the clayey soils at Alappad Kole. Prototype of the self propelled cono weeder was developed and field tested. It works satisfactorily in a single forward pass, and covers an area of 0.1 ha h-1. The field study showed that the self propelled cono weeder is effective for inter row weeding in rice, however, further refinement is needed to improve its weeding efficiency.