An artificial capillary barrier to improve root zone conditions for horticultural crops: physical effects on water content

Capillary barriers (CBs) occur at the interface of two soil layers having distinct differences in textural and hydraulic characteristics. The objective of this study was to introduce an artificial CB, created by a layer of gravel below the root zone substrate, in order to optimize conditions for the cultivation of horticultural crops. Potential root zone formats were analyzed with and without the gravel CBs for variables including the following: depth of CB; barrier separating the root zone from the surrounding soil; and root zone soil texture. Field and simulated results revealed that artificial CBs increased root zone water content and changed water flow dynamics. Volumetric soil water content was increased by 20–70%, depending on the soil texture and depth of the barrier. Sandy soil texture and shallower placement resulted in relatively higher water content. For sandy soil without plants, a shallow (0.2 m depth) CB increased water content of the overlaying soil by 50% compared to the control. The introduction of a gravel CB below the root zone of pepper plants (Capsicum Annum L.) lead to 34% higher matric head, 50% lower diurnal fluctuations in matric head and 40% increase in pepper fruit yield. Increasing water content by way of artificial CBs appeared to improve the water use efficiency of pepper plants. Such an improvement could lead to reduced water and fertilizer application rates and subsequent reduction in contamination below the root zone. This is especially relevant for substrates of low water-holding capacity typically used in horticulture crop production.     

Productivity of greenhouse roses following changes in soil moisture and soil air regimes

Following 2 years of different soil moisture and air regimes for ‘Baccara’ roses, the optimal regimes were chosen and kept uniform for each growth medium. These regimes were implemented for an additional year (1971–1972).Soil moisture and soil air regimes employed in previous years (1969–1971) had significant after-effects on flower yields in 1971–1972, but no effect on flower quality or weight. The effect of previous suboptimal moisture and air regimes was apparently due to the number of main branches formed per plant in the initial two years, which was unaffected after implementation of optimal regimes.Approximately 4 weeks after cessation of cutting, the root system consituted 11–15% of the total weight of the plant. While 65% of the root system in non-separated beds was located in a soil layer between 30 and 60 cm, only 27% were located above this layer.     

Numerical investigation of irrigation scheduling based on soil water status

Improving the sustainability of irrigation systems requires the optimization of operational parameters such as irrigation threshold and irrigation amount. Numerical modeling is a fast and accurate means to optimize such operational parameters. However, little work has been carried out to investigate the relationship between irrigation scheduling, irrigation threshold, and irrigation amount. Herein, we compare the results of HYDRUS 2D/3D simulations with experimental data from triggered drip irrigation, and optimize operational parameters. Two field experiments were conducted, one on loamy sand soil and one on sandy loam soil, to evaluate the overall effects of different potential transpiration rates and irrigation management strategies, on the triggered irrigation system. In both experiments, irrigation was controlled by a closed loop irrigation system linked to tensiometers. Collected experimental data were analyzed and compared with HYDRUS 2D/3D simulations. A system-dependant boundary condition, which initiates irrigation whenever the matric head at a predetermined location drops below a certain threshold, was implemented into the code. The experimental model was used to evaluate collected experimental data, and then to optimize the operational parameters for two hypothetical soils. The results show that HYDRUS 2D/3D predictions of irrigation events and matric heads are in good agreement with experimental data, and that the code can be used to optimize irrigation thresholds and water amounts applied in an irrigation episode to increase the efficiency of water use.     

Molecular detection of Anaplasma phagocytophilum in cattle and Ixodes persulcatus ticks

The tick-borne pathogen, Anaplasma phagocytophilum (A. phagocytophilum), the causative agent of human granulocytic anaplasmosis (HGA), is increasingly becoming a public health concern as an aetiological agent for emerging infectious disease. We found A. phagocytophilum infection in a pooled sample of field-collected Ixodes persulcatus (I. persulcatus) ticks from one district in Hokkaido, Japan. Thus, to further investigate the prevalence in field-collected ticks, we used PCR assays targeting the A. phagocytophilum gene encoding 44 kDa major outer membrane protein (p44) for screening of I. persulcatus ticks and samples from cattle from pastures. Out of the 281 I. persulcatus ticks, 20 (7.1%) were found to harbor A. phagocytophilum DNA. The infection rate for A. phagocytophilum in cattle was 3.4% (42/1251). In future studies, it will be necessary to investigate effects of the infection in order to understand its pathogenesis of A. phagocytophilum in domestic animals.     

Flower bud atrophy in ‘Baccara’ roses. I. Description of the phenomenon and its seasonal frequency

“Blind” shoot formation in roses is described as being caused by flower bud atrophy. The frequency of the phenomenon is influenced by the location of the bud from which the shoot breaks and by seasonal conditions. The frequency of “blindness” is higher in the winter, and is higher when the shoots are lower on the branch. Winter drop in flower production is not always accompanied by an increased percentage of bud atrophy, since lack of flowering may also be due to a lower rate of bud breaking.The chlorophyll and anthocyanin contents in leaves of flowering shoots are higher than those of non-flowering ones.     

Controlling the growth and development of rose plants after planting

The effects of pinching and lateral bud removal (deshooting) on the development of structural shoots, the number of flowers, and the average flower stem length in young rose plants were examined, using the cultivars ‘Baccara’, ‘Sonia’ and ‘Belinda’. The effect of deshooting on flower yield varied with each cultivar. It did not affect the number of ‘Baccara’ flowers, but increased ‘Sonia’ and ‘Belinda’ flower production by 50% and 75%, respectively. Leaving flowers to bloom out on plants before the start of commercial harvest resulted in a decrease in the length of the flower stems and also reduced the beneficial effect of deshooting on flower yield. Deshooting enhanced structural shoot formation (“bottom breaks”). Pinching flower buds of structural shoots increased the number of ‘Baccara’ flowers in comparison with pruning these shoots to 40–60 cm, as in common practice. Deshooting of the structural shoots of ‘Sonia’ and ‘Belinda’ increased the number of flowers in both cultivars.     

非饱和土壤水运动模型参数优选方法研究

针对数值反演过程中参数优选方法适用性不明确的问题,研究最小化目标函数、带有自适应差分演化Metropolis的马尔可夫链蒙特卡罗方法(MCMC-DREAM)对数值反演效果的影响,为探索高效的参数优选方法提供参考。数值算例反演结果表明:最小化目标函数方法计算复杂度较低,但对参数初值敏感,适合于对目标区域土壤有较为深入了解的场合使用;MCMC-DREAM对参数初值不敏感,但计算复杂度较高,适合于先验信息有限的场合使用。两种参数优选方法都存在“异参同效”现象,先验信息与敏感性分析有助于克服该问题,提高数值反演解决实际问题的能力。     

The potential of transforming simple structured pine plantations into mixed Mediterranean forests through natural regeneration along a rainfall gradient

The aim was to study the potential for using natural regeneration as a basis for transformation of simply structured conifer plantations into mixed Mediterranean forests. We studied the variation along a rainfall gradient, in the natural regeneration of tree species in the understory of planted 40- to 50-year-old Aleppo pine (Pinus halepensis) forests. The study was conducted within the Mediterranean zone of Israel, which extends from the semiarid northern Negev desert (rainfall ca. 300 mm yr⁻¹) in the south to the humid Upper Galilee in the north (ca 900 mm yr⁻¹). Cover and height, density, and species composition of regenerating trees were measured on south- and north-facing slopes in forest sites of comparable silvicultural history (site preparation methodology, planting density and thinning regime) distributed along the rainfall gradient. Altogether, 12 species of regenerating native broadleaved trees were found in the understory of the various forest sites. Surface cover, density and species richness increased linearly along the entire rainfall gradient, on both north- and south-facing slopes, ranging from zero in the driest forest sites up to 85% cover, 7980 trees ha⁻¹ and 4.5 species per 200 m², respectively, in the most humid ones. Species composition of regenerating trees was also related to rainfall amount, through changes in the relative importance of species along the rainfall gradient. The effect of topographic aspect on tree regeneration was inconsistent, i.e., the interaction Rainfall × Aspect was significant. Nevertheless, the general trend showed better regeneration on north-facing slopes. Most of the regenerating trees in the understory were small, i.e., less than 100 cm in height, with no clear effect of rainfall amount and topographic aspect on the relative abundance of height classes. Regeneration by Aleppo pine was highly variable among and within the different forest sites and ranged from 0 to 1565 trees ha⁻¹, with no clear relationships with rainfall amount and topographic aspect. In light of our results we propose that the future structure of forests should vary with respect to annual rainfall amount within possible silvicultural scenarios.     

The response of rose plants to evaporative cooling: Flower production and quality

The effect of evaporative cooling in a compartmentalized greenhouse on the flower production and quality of 4 rose cultivars was investigated during 2 cutting-seasons.Evaporative cooling reduced flower formation of all rose cultivars tested, regardless of their location in the greenhouse. This reduction was ascribed to the decrease in growth rate of rose shoots resulting in fewer flowering-flushes than in the uncooled control plants during the same time period.Flower quality, however, was significantly improved under evaporative-cooling conditions. This was apparent in an increase in weight of the entire flower as well as in unit of flower-stem length. Weight of the flowering-bud was less affected, and was increased during the autumn and spring seasons only. Anthocyanin content of flower petals was increased by evaporative cooling, especially during the summer.     

An artificial capillary barrier to improve root-zone conditions for horticultural crops: response of pepper, lettuce, melon, and tomato

Capillary barriers (CBs) occur at the interface between two soil layers having distinct differences in hydraulic characteristics. In preliminary work without growing crops, it was demonstrated that CBs implemented in sandy soils increased hydrostatic volumetric water content by 20–70%, depending on soil texture and depth of barrier insertion. We hypothesized that the introduction of an artificial CB at the lower root-zone boundary of horticultural crops can increase yields as a result of increased water content and uptake efficiency. The effects of introduced CBs on soil water content, plant growth, and yields of bell peppers (Capsicum annum L), lettuce (Lactuca sativa L), tomatoes (Lycopersicon esculantum L.), and melons (Cucumis melo L.) were studied in a desert environment in southern Israel. Inclusion of a CB increased soil water content by 60% and biomass and fruit yields by 25% for pepper, and increased matric head and biomass yield by 80 and 36%, respectively, for lettuce. Neither tomatoes nor melons reacted significantly to the presence of CBs, in spite of increased soil moisture. Daily soil matric head amplitude was reduced fivefold when lettuce was grown with a CB. Spatial variability was highly reduced when a CB was present. When peppers were grown with a CB, the standard deviations of water content and biomass yield were reduced by 40% relative to control.