Control of some soilborne pathogens may be achieved by use of decoy or catch crops. These stimulate the germination of resting spores, resulting in limited expression of disease symptoms. Results achieved using this approach are reported here using leafy daikon (radish, Raphanus sativus var. longipinnatus) for control of Plasmodiophora brassicae, the cause of clubroot disease of Brassicaceae. Disease indices of Chinese cabbage plants grown in pots that had previously contained leafy daikon were lower compared with pots where no plants had been grown before (control pots). Numbers of resting spores of P. brassicae in soil in pots after cultivation with leafy daikon were reduced by 71% compared with control pots when resting spores were recovered and counted directly. In a field experiment, numbers of resting spores were reduced by 94% compared with the start of the experiment when leafy daikon was grown in advance of Chinese cabbage, but there was no reduction in disease severity in the Chinese cabbage. Plasmodiophora brassicae infected the root hairs of leafy daikon and those of Chinese cabbage, but no clubs were found on leafy daikon roots. The results from pot trials indicate that leafy daikon may be useful as a decoy crop for the control of clubroot disease in field crops.
Saline soils occur extensively in Northeast Thailand. As the climate of this region is clearly differentiated into dry and rainy seasons, salts in the groundwater move up and accumulate on the soil surface during the dry season and are leached down with rainfall during the rainy season. In this paper, the physical and chemical properties concerned with salt movement were investigated for the saline soils in the Khon Kaen Region, Northeast Thailand. Changes in the physical and chemical properties with leaching were also studied in order to determine the effect of rainfall on desaltation. The saline soils in the Khon Kaen Region are generally sandy with low CEC, low content of organic matter and low buffering capacity. The dominant salt is NaCl, which facilitates the dispersion of clay. The main types of clay minerals are I : I type. All the soils contained large amounts of quartz, indicating that they are highly weathered soils. The amount of materials dispersed by water leaching, mainly clay, accounted for the large percentage of clay and silt fractions.
Chemical properties of Pretreatment center slag (PTC-slag) were analyzed and compared to those of converter slag (C slag) and blast furnace slag (BF slag). PTC slag had a high EC value as well as citric acid soluble P and contained more Ca, Si, P, K, and Na but less Mg and Fe than C slag. Compared to BF slag, PTC slag contained more Fe, Ca, Mg, P, Mn, and Na but less Si, Al, and K. Although neutralizing value of PTC slag was lower than that of C slag, its ability to neutralize soilacidity was markedly higher. A pot experiment using Andisol from Tochigi Prefecture and komatsuna plant was carried outto evaluate PTC slag as liming material as well as P fertilizer. PTC slag, C slag, and dolomite were applied as liming materials and combined with super phosphate (SP). Addition of SP of 2.5 and 5.0% phosphate absorption coefficient (PAC) to PTC slag significantly improved the yield of komatsuna.This result, however, only apply for PTC slag adjusting soil pH to 6.5. Addit~ono f the same dosage of SP to PTC slag adjusting soil pH to 7.5 did not give significant effect. On the other hand, addition of SP of 2.5 and 5.0% PAC to C slag or dolomite significantly improved the yield for both C slag ordolomite adjusting. the soil pH to 6.5 and 7.5. Results of the experiment also indicated that P'TC slag and C slag significantly increased soil pH; exchangeable Ca, and Mg and improved available P, B, and Mn in Andisol. The magnitudes ofthese effects of the two slags, however, were difference. As compared to C slag and dolomite, PTC slag increased lower exchangeable Mg but higher available P. These results suggest that for acid soil amendment, PTC slag was better than dolomite and C slag due to the fact that this material supplymore P and B. Application of PTC slag as acid soil amendment will reduce the demand of P fertilizer, and even in high dosage can meet the P demand of komatsuna plant.
Reconstruction support of the disaster-stricken areas in the city of Soma, Fukushima Prefecture, was started in May 2011. Sediment transported from the sea by the tsunami was from 5 to 10 cm thick on surface of the paddy fi elds. The tsunami sediment was mixed with the original soil of the paddy fi elds, and mole drains were formed to improve water drainage toward the lower layer. Subsequently, rainwater alone was used for salt removal. However, the pyrite in the soil had gradually oxidized until the pH dropped to 3.8, so converter slag was applied to neutralize the sulfuric acid. In May 2012, rice was transplanted into paddies from which the salt had been removed. On September, 10.7 t brown rice was harvested. The yield of brown rice harvested per hectare was 6.3 t, about 20 % higher than the amount before the disasters.
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