Growth management of vetiver (Vetiveria zizanioides) under Mediterranean conditions.
ABSTRACT In spite of the advantages of Vetiver grass in light of environmental aspects, this plant is not used in the Mediterranean region. The objectives of the present study were: (i) to elucidate growth parameters and establishment of Vetiver under Mediterranean conditions suitable for its various environmental applications; and (ii) to develop management practices for growing vetiver under Mediterranean conditions. In greenhouse experiments conducted under controlled conditions it was found that, in general, increasing the minimum/maximum temperatures to 21-29 degrees C significantly increased plant height. In the Mediterranean region, this range of air temperatures is obtained mainly during the summer, from June to September. For air temperatures up to 15-23 degrees C the effect of day length on plant height was insignificant, whereas in air temperature >15-23 degrees C, the plant heights under long day conditions were significantly higher than under short day. The number of sprouts per plant increased exponentially with increasing air temperature, and was not significantly affected by the day length at any air temperature range. In open fields, the heights of irrigated vetiver plants were significantly higher than those of rain-fed plants. It was concluded that, once they were established, vetiver plants could survive the dry summer of the Mediterranean region under rain-fed conditions, but they would be shorter than under irrigation. Cutting or burning of the plant foliage during the spring did not improve the survival of vetiver during the dry summer. In order to obtain fast growth of vetiver and to increase the possibility of its using the rainwater, the plants should be planted in the winter, during February and March. However, under this regime, the vetiver plant cannot be used as a soil stabilizer during the first winter, because the plant is still small. In contrast, under irrigation it is advantageous to plant vetiver at the beginning of the summer; the plant then has sufficient time to grow and develop before the beginning of the winter, so that its effect as a soil stabilizer in the following wet winter could be maximal. It was found that vetiver could grow in a wide range of substrates, such as: sandy soil, loamy sand, clay soil, crushed limestone, sandy clay loam, and tuff/peat mixture.
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ABSTRACT: The infiltration of rainfall into bare soil was studied in field and laboratory experiments on two soil types in Israel.The main governing process is the formation of crust with an hydraulic conductivity several orders of magnitude lower than that of the soil profile. The decrease in conductivity is attributed to the organization of a very thin layer on the soil surface. The sealing efficiency of the crust is achieved by suction forces which arrange soil particles, probably clay, into a continuous, dense layer.The decrease in flux through the crust creates conditions of unsaturated flow in the soil profile below the crust.The dynamics of the hydraulic relationship between the soil profile and the crust during a rain storm was analyzed by means of an analytical model.Journal of Hydrology. 01/1981;
- Australian Journal of Soil Research - AUST J SOIL RES. 01/2002; 40(3).
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ABSTRACT: particles into the upper few millimeters of the soil, and deposition in the voids; and (iii) compaction of the soil Soil mineralogy and texture have substantial effects on aggregate surface to form a thin film, which restricts further entry stability and, therefore, may influence infiltration rate (IR) and soil of water and movement of soil particles. loss under rainfall. The objective was to study the effects of soil Two main types of soil crust, namely structural and mineralogy and texture on crust micromorphology, infiltration, and erosion. Five soils with differing properties were subjected to 80 mm depositional crusts, are generally recognized, according of simulated rainfall. The aggregate stability of these soils was deter- to their mechanisms of formation (Chen et al., 1980). mined by the fast wetting method. The mean-weight diameters of the Structural crusts are due mainly to water-drop impact, particles after the fast wetting were 2.8 mm in the clayey kaolinitic whereas depositional crusts are formed by translocation soil, 0.25 and 0.31 mm in the clayey and sandy loam montmorillonitic of fine particles and their deposition at some distance soils, respectively, and 0.84 and 0.87 mm in the clayey nonphyllosili- from their original location. In contrast, Valentin and cate soils. The final IR was 20.5 mm h 1 in the clayey kaolinitic soil Bresson (1992) classified crusts into three main groups: and9.3 mm h 1 in the remaining soils. Scanning electron microscope structural, depositional, and erosional crusts, of which (SEM) observations indicated that the kaolinitic soil had a thin crust the last are formed through erosion of the sand layer at (0.1 mm) containing large particles (0.1 mm), whereas the montmo- the top of the structural crust, following runoff initiation. rillonitic soils had thicker crusts (0.2 mm) comprising either small Luk et al. (1990) subjected some loess soils, domi- (0.02 mm) particles with a very developed washed-in zone under- nated by illite and kaolinite minerals, to rainstorms of neath or large (0.2 mm) ones with fine material between them. a range of durations. Scanning electron microscope ob- The crust layer in the nonphyllosilicate soils was 0.2 mm thick and servations of the crusts in these soils revealed a re-Soil Science Society of America Journal - SSSAJ. 01/2002; 66(3).