Evaluation of optimum soil moisture levels at which striga asiatica (L.) and rhamphicurpa fistulosa (hochst.) benth. can establish a relationship with a host
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Date
2014
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Sokoine University of Agriculture
Abstract
Pot experiments were conducted in a screen house to determine the optimum moisture levels required for either of the parasitic weeds, singly and in combination, to establish a relationship with rice. Studies were conducted in Morogoro, Tanzania, (525 m.a.s.l., 6°45” S and 37°40” E) September, 2012-February, 2013. Ten-litre plastic pots capacity filled with dry 5:1 (sand: clay) soil mixture up to 2cm below the rim were used. Treatments were arranged in split- plot with plant combinations (Rhamphicarpa+r\ce, Rhamphicarpa alone, Striga+rice, rice alone) as the main plot and moisture levels (saturation, field capacity, field capacity/saturation and field capacity/wilting point; the latter two were half way in between) as subplots. Rice variety ‘Supa India’ was used and treatments were arranged in a randomized complete block design with five replicates including a duplicate that was used for destructive sampling. Emergences of Rhamphicarpa were not significantly affected by moisture levels, however, the significant differences were observed on emergence of Striga asiatica. At 60 and 120 DAS, there were significant differences in weed counts at different moisture levels whereby 60 DAS, the maximum Rhamphicarpa counts was 40 and at 120 DAS the maximum Rhamphicarpa counts was 7.8 plants appeared in saturation moisture level. Striga at 60 DAS, showed significant differences in number at different moisture levels whereby at field capacity/wilting point 3 plants were recorded while at 120 DAS the maximum Striga number (9) was recorded at field capacity moisture level. Weed heights at 60 DAS was significant different in moisture levels whereby the tallest Rhamphicarpa plant (16.3cm) was recorded at saturation while for Striga (13.2cm) at field capacity/wilting point. Rhamphicarpa flowering took place at 76 DAS while Striga flowered at 83DAS.The rice damage caused by weeds at different moisture levels were observed in different areas whereby there was significant different in plant heights and the tallest rice plants (86.6cm) were recorded at saturation moisture level and Striga/rice plant combinations 60 DAS while at 120 DAS the tallest plant (119.5cm) was recorded at same moisture level and plant combination. Rice chlorophyll content (SPAD), stomatai conductance (mmol/(m2-s) and in tiller numbers were significantly different however, there was no significant difference in leaf area(cm2), specific leaf area (cm2.g'*) and in chlorophyll fluorescence (fv/fm).Weeds affected rice biomass where by R. fistulosa lowered rice biomass to 2.5g compared to rice planted alone (5.2g) and (5.06g) when planted with Striga at 60 DAS at saturation moisture level while at field capacity, Rice alone produced 2.86g, Rhaniphicarpa/ncQ 1.2g and 1.6g for Striga/rice; this trend was observed at 120 DAS. The results conclude that moisture has effect to weed performance whereby Rhamphicarpa performed well in saturation moisture level while Striga preferred field capacity and field capacity/wilting point. Also Rhamphicarpa plants in field capacity/saturation caused same damage to rice plant as for Striga which tells that they can co-exist at field capacity/saturation.
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Dissertation
Keywords
Soil moisture, Maize, Parastic weeds, Striga asiatica, Rhamphicarpa fistulosa, Morogoro