Estimation of relative water use among ornamental landscape species

Low water use plantings may enhance water conservation in dry landscapes. However, appropriate plant selection is hindered by the dearth of information available on the water needs of different species. A direct method of classification was tested under the hypothesis that relative water use by woody landscape species growing in 3.8 l containers would be representative of the water use of the same species in the landscape. Four species of distinctly different ecological origin (Leucophyllum frutescens, Spiraea vanhouteii, Viburnum tinus, Arctostaphylos densiflora) were chosen in order to obtain a wide range of responses, and their water use was measured in plants growing in 3.8 l containers and compared to that of the same species growing in drainage lysimeters, representative of landscape conditions. Half of the plants were subjected to successive cycles of stress by withholding water after irrigation to container capacity in containers, or applying a fraction of the potential evapotranspiration in lysimeters. The good fit of the regression of average daily water use by lysimeter plants on average daily water use by container plants (R²=0.87,P<0.01) reflects the consistency of relative water use of the four species. Measurement of water use at the end of nursery production may be useful for predicting the relative water use of various species after establishment in the landscape.     

苹果容器苗在连作土壤上的生长表现及其根区土壤环境特征

以苹果红露/M9-T337为试材,用小、中、大3种规格(上部直径分别为10、20和30 cm,底部直径为8、16和24 cm,高均为30 cm)容器育苗,将其连同基质一起移栽入25年老龄苹果园树穴中,以裸根苗为对照,分别在6个月和18个月后观察苗木生长和根区土壤环境特征.结果 表明:带基质的容器苗均不同程度地改善了连作...     

An integrated method for irrigation scheduling of potted plants

Hourly meteorological and soil water potential data collected during the summer season on a container crop of 2-year-old plants of Hypericum hidcote were used to develop a methodology that integrates climate-based (AET = ETo × K_c) and soil-based methods (soil water potential measurements by tensiometers) for the automatic control of the irrigation of plants growing in pots. Hourly ETo values were calculated by the CIMIS equation, derived from the Penman formula. Tensiometric data, by a soil-specific tensiometric curve, were transformed into pot water weight and used to estimate actual hourly evapotranspiration (AETt).     

定向出菇技术对香菇产量和品质的影响

为了摸清定向出菇新技术对香菇(Lentinula edodes)产量和品质的影响,以传统免割保水膜袋法为对照,开展了定向出菇新技术的出菇试验。试验选用2个香菇品种L808和兴农1号,统计香菇产量,测量子实体形态的变化。结果表明,定向出菇新技术在产量上的表现因品种而异,对于品种L808,采用2种栽培方式,其产量持平;而对于品种兴农1号,采用定向出菇技术栽培的产量显著高于传统免割保水膜袋法;新技术在单菇重、菌盖直径等子实体形态特征指标方面优于传统的免割保水膜袋法。研究表明定向出菇新技术可用于香菇栽培。     

The Phytophthora diseases of apple

The most important Phytophthora pathogens of apple are P. cactorum and P. syringae, although other species may be locally significant. P. cactorum is widespread in the apple growing regions of the world and causes girdling bark rots on the scion (collar rot) and on the rootstock (crown rot), necrosis of the fine root system (root rot) and fruit rot. P. syringae is a significant pathogen of apple only in north-western Europe, where it causes collar rot but is most damaging as a cause of rot in stored fruit. Several other species of Phytophthora have been implicated in crown rot and root rot.

Bark rots due to Phytophthora spp. have distinctive features, such as mottled green/ orange/brown coloration of necrotic tissue, but may be confused with other causes of bark death. Isolation of the pathogen is therefore essential for diagnosis, and is now made easier than formerly by the use of selective media. Phytophthora fruit rot is usually distinctive, and isolation from diseased tissue is readily achieved by conventional methods.

P. cactorum and P. syringae are homothallic, soil-borne species. The principal peren- nating structure is the oospore. Zoospores are the main infective structures and are relatively short-lived. Mycelium and sporangia have intermediate survival characteristics. The longevity of ephemeral stages is favoured by moderate soil moisture and low temperatures. Growth and reproduction is associated with the colonization of living tissues. The two species have different temperature/growth characteristics. Oospore germination and sporangium production require soil moisture near to saturation, while zoospore release and motility depend on the presence of free water. The flexible growth response of these pathogens permits them to cope with fluctuating soil conditions.

P. cactorum and P. syringae cause diseases of a range of other economic plants, woody and herbaceous. There is evidence for host adapted strains in P. cactorum.

Phytophthora pathogens may be present in the soil when apples are planted or enter with planting material, in irrigation water, on animals or on implements. Once present, they may regenerate and produce durable increases in inoculum content of soil by colonizing live, abscissed apple organs such as leaves and fruit. Other plant species in orchards may also be important in inoculum regeneration.

Infection of unthickened tissues is direct or via stomata or lenticels. Bark may be infected directly through wounds, growth cracks or lenticels, or indirectly via unthickened roots.

Growth of the pathogens in host tissues is intercellular and intracellular. Susceptibility to bark rot is related to the effectiveness of phelloderm barriers in walling-off fungal growth. Attempts to relate the biochemical constituents of bark to resistance have been inconclusive.

Disease incidence and development is affected by the availability of water above ground and in the soil, soil type, tree age, the height of the graft union, the interaction between scion and rootstock and soil management techniques. Seasonal influences on disease reflect climatic effects on pathogen activity and cyclic changes in tissue resistance. Bark diseases due to P. cactorum are associated with the growing season, while those due to P. syringae are associated with dormancy of the host.

Host resistance and the manipulation of cultural conditions are the most effective means of disease control. The early selection for resistance in breeding material is complicated by the fact that susceptibility to collar rot develops only in mature trees, and the conditions required to induce crown rot experimentally in susceptible rootstocks are not fully understood. Other methods of control are the use of chemicals protectively or cura- tively and the use of Phytophthora-iree planting material. The possibilities of biological control are at an early stage of investigation.     

The effect of container size and aeration conditions on growth of roots and canopy of woody plants

Studies were made on the effect of container size on the growth of Ficus retusa, Pistacia lentisucus and Dodonea viscosa. The larger the container, the larger was the plant. The ratio of plant weight to unit of container-volume decreased with increasing size, whereas the ratio of plant weight to unit surface area remained more or less constant with changing size of container.Aeration of 10-liter containers using 3 methods to increase the surface area of the mixture by 60% while reducing the volume by 40%, increased growth by as much as 165%. Especially enhanced growth was achieved when the structure of the root system was not changed by aeration devices. Root growth was enhanced most in the lower section of the containers. The ratio root-weight: container-volume increased up to 340%, whereas the ratio root-weight: mix-surface area increased by only 100% at the most.These results, and others, indicate that most of the thin roots (or root activity) of woody plants grown in containers are concentrated in the periphery of the container, whereas the roots in the center serve mainly as connectors between the main and peripheral roots.It is suggested that the root system in the containers changed the ratio between the 3 soil phases by decreasing the gaseous phase, mainly in the upper part of the container, and that this phenomenon is a major contributor to the low efficiency of the container-volume usage. Correction can be best achieved by increasing the outer surface of the mixture rather than by using a better aerated mixture.     

Suitability of wood fiber substrate for production of vegetable transplants: I. Physical properties of wood fiber substrates

Several experiments were conducted with the objective to find suitable alternatives for peat substrates. Physical properties of wood fiber substrates in comparison to other organic substrates were examined. Volume weight, total pore space, pore size distribution, available water, container and air capacity, saturated hydraulic conductivity and volume loss of these substrates were determined. Wood fiber substrates showed a similar volume weight and total pore space as peat substrates, but lower water retention. Particularly the drainage performance of wood substrates results in a quick drainage of surplus water. An increase of volume weight caused a decrease of total pore space, air content and saturated hydraulic conductivity and an increase in water retention. Evaluation of these parameters under container conditions is critical since they are directly related to irrigation and therefore to plant growth. A compression of wood fiber substrates in the pots is recommended to minimize substrate loss. An increase of compression levels reduced the volume loss to almost 0 vol.%. The effect of wood fiber substrates and their volume weight on plant growth will be reported in a second paper.     

Assessing topographic patterns in moisture use and stress using a water balance approach

Through its control on soil moisture patterns, topography’s role in influencing forest composition is widely recognized. This study addresses shortcomings in traditional moisture indices by employing a water balance approach, incorporating topographic and edaphic variability to assess fine-scale moisture demand and moisture availability. Using GIS and readily available data, evapotranspiration and moisture stress are modeled at a fine spatial scale at two study areas in the US (Ohio and North Carolina). Model results are compared to field-based soil moisture measurements throughout the growing season. A strong topographic pattern of moisture utilization and demand is uncovered, with highest rates of evapotranspiration found on south-facing slopes, followed by ridges, valleys, and north-facing slopes. South-facing slopes and ridges also experience highest moisture deficit. Overall higher rates of evapotranspiration are observed at the Ohio site, though deficit is slightly lower. Based on a comparison between modeled and measured soil moisture, utilization and recharge trends were captured well in terms of both magnitude and timing. Topographically controlled drainage patterns appear to have little influence on soil moisture patterns during the growing season. In addition to its ability to accurately capture patterns of soil moisture in both high-relief and moderate-relief environments, a water balance approach offers numerous advantages over traditional moisture indices. It assesses moisture availability and utilization in absolute terms, using readily available data and widely used GIS software. Results are directly comparable across sites, and although output is created at a fine-scale, the method is applicable for larger geographic areas. Since it incorporates topography, available water capacity, and climatic variables, the model is able to directly assess the potential response of vegetation to climate change.     

Growth of vetivergrass for cutslope landscaping: Effects of container size and watering rate

A slope greening technique using vetivergrass has been adopted in Hong Kong on shotcreted surfaces. Vetiveria zizanioides (L.) Nash is the most commonly used species. Soil packed PVC tubes of 250 mm long and 150 mm in diameter are installed on slopes to form planters for vetivergrass growth. However, there is a paucity of information on the optimal tube size for grass growth. Together with soil characteristics, tube size determines water and nutrient availability and the space for growth. This study aimed to assess the suitability of containers of different height and diameter, and the effects of different watering rates on the growth of vetivergrass in a greenhouse experiment. Seven container dimensions and three watering rates were evaluated, and the growth of vetivergrass was measured every three months in terms of aboveground biomass for a year, while underground biomass was determined at the end of the experiment. In general, increasing water supply, diameter and height supported a denser cover of vetivergrass for the purposes of erosion control and decorating hard surface of cutslopes. Vetivergrass grew better when watered at rates equivalent to 1× and 2× the amount of annual precipitation than that at 0.5×, but the effect of watering diminished with decreasing diameter and height. Grass dry matter production increased with the diameter and, to a lesser extent, height of the PVC tubes. If watering is not possible, i.e. under 0.5× or 1× watering rate, a PVC tube with 250 mm height and 150 mm diameter seems to be the most suitable container. On the other hand, if irrigation is feasible, a smaller container can be used without detrimental effect on grass growth.     

水氮互作对红枣光合特性与产量的影响

以滴灌为条件、设置不同水肥处理,研究水氮互作对红枣光合、产量与品质的影响。结果表明:土壤中增施氮素有利于枣树叶片的净光合速率,而增加土壤水分则会导致枣树叶片的蒸腾速率增大;在设计水平范围内,增加土壤含水量会降低红枣果实的单果重和果形指数;水和氮的产量效应趋势均呈抛物线形,水的正效应和负效应都相对明显,而氮肥的正效应明显,负效应平缓;土壤水分和氮素含量过高会降低红枣果实还原糖与VC含量,蛋白质的含量却随着土壤中氮肥量的增加而增加。     

The effect of container shape on the development of roots and canopy of woody plants

The branching and spread of roots in containers was studied in a shallow rooting plant (Erythrina corralodendrum) and in a deep-rooting plant (oak, Quercus ithaburensis). In the Erythrina, the weight of the roots was found to decrease towards the base of the container. Sixty percent of the root system was laterals, which were evenly distributed throughout the container. In the oak, a higher root weight was found in the lowest third of the container than in the 2 upper thirds. Lateral roots comprised 14% of the complete root system, mostly in the base of the container. Severe pruning of oak roots resulted in a ratio of main-root/lateral roots comparable to that found in unpruned Erythrina.The growth and distribution of roots of plants with different growth characteristics in containers of various shapes, e.g. deep and narrow, or shallow and wide as compared to regular shape containers, were studied. Thus, in Ficus retusa, which has a shallow root system, the development of roots was stimulated in a shallow and wide container, but roots and canopy were restricted in a deep and narrow container. In Pistacia lentiscus, which has a deep root system, planting in a shallow and wide container resulted in retarded canopy and roots, while growing the same plant in a narrow and deep container showed a stimulated root growth. In Dodonea viscosa, whose root system is naturally deep and tends to spread laterally, a slight retardation of the root development was found when it was grown in a shallow and wide container. When grown in a deep and narrow container, canopy and root growth were stimulated.The study indicated that growth tends to be stimulated when there is a mutual matching between the natural growth pattern of roots and the shape of their container.     

以金针菇菌糠为培养基质的猴头菇高效栽培技术

以猴头菇为研究对象,采用金针菇菌糠、滤泥等廉价培养基质,通过优化液体菌种和栽培培养基配方、栽培方式等建立猴头菇高效栽培技术体系.结果表明,猴头菇液体菌种的培养基配方为H3,培养到第4天时活力最强;猴头菇栽培培养基配方W2;栽培方式以小口径、不需要搔菌为好;比较菌糠培养基与纯玉米芯培养基栽培获得的子实体,金针菇菌糠培养基...     

The Relative Importance of Stem and Root in Determining Rootstock Influence in Apples

Young clonal cacao trees have been grown under controlled soil moisture conditions for 20 months in a glasshouse. Weighable soil containers were used, and water was added to restore the soil to field capacity each time the total available water, which was about 40 lb. for each plant, had been depleted to 85% (wet treatment), 50% (medium treatment) or 15% (dry treatment). Plants were either given one of these treatments for the whole experiment, or one treatment was given during the natural dry seasons and another during the natural wet seasons.

Plants given a dry treatment at any time lost their apical dominance and flushed vigorously about 10 days after each watering, though many flushes subsequently withered. The other plants flushed normally, except that the continuously wet plants ceased to flush towards the end of the experiment. The mean expanded area of each leaf was greatest during wet and least during dry periods, and plants which had suffered the least soil moisture deficit throughout growth had the greatest net leaf area and dry weight accumulation. There was little difference in the rate of transpiration per unit leaf area between plants during periods of high compared to medium soil moisture, but the rate was less during dry periods. Dry weight increases both per unit of water transpired and per unit of net leaf area were greatest in the wettest plants.

There was little difference between the effects of the wet and the medium treatments on flower production or setting or on cherelle wilt, though ultimately slightly more pods ripened on the wet plants. Plants in a dry period developed few flowers, but initiation was apparently stimulated, for in a subsequent wet or medium period flowering was exceptionally heavy ; setting was poor and cherelle wilt high, however.

It is concluded that irrigation on a greater scale than is practised at present is likely to be beneficial to the growth and yield of cacao.     

Propagation of Black Currants from Single-Bud Cuttings

Black currants are readily propagated from single-bud hardwood cuttings approximately i inch long, with the bud at the top and planted vertically. The best part of the shoot from which to take such cuttings is the lower- mid portion (buds 15-22).

Optimum rooting is obtained from cuttings planted in January, February and March after dormancy has broken in the field, but by using 24-hour day-length successful rooting can be extended from October to March. The emergence of flowers in March-planted cuttings slightly reduces rooting.

Thirteen commercial varieties have been propagated successfully by this method.

Suitable softwood and semi- hardwood cuttings are available when the current season's shoots are 12 nodes or more in length, i.e. normally in late April. When these are planted in a propagation frame with soil heating, good rooting is obtained from April to June provided the subtending leaf is retained during the rooting period.

Twenty-four-hour day-length increases the rooting of cuttings planted in July; lack of rooting after July is attributed to early leaf abscission, the initiation of flowers and the onset of dormancy.     

Nitrogen and water use efficiency of zucchini squash for a plastic mulch bed system on a sandy soil

Zucchini squash (Cucurbita pepo L.) is an economically important vegetable crop in Florida. Typically, it is intensively managed with high inputs of fertiliser and irrigation water. Our objectives were to evaluate the interaction between fertilisation rates and irrigation treatments, and to quantify nitrate leaching in a plastic mulched/drip irrigated zucchini squash production systems. Three studies were carried out. The first study evaluated different depth placement of drip and fertigation lines on plant growth and fruit yield. Treatments included SUR (both irrigation and fertigation drip lines placed on the surface); S&S (both lines buried 0.15 m deep); and SDI (irrigation line placed 0.15 m below the fertigation line on the surface). The second and third studies compared three different N-rates and different soil moisture sensor-based irrigation strategies. Nitrate-N leaching was monitored by zero tension drainage lysimeters and soil samples. N leaching increased when irrigation and N-rates increased, with values ranging from 2 to 45 kg ha⁻¹ of N. Use of SDI increased yields by 16% compared to the S&S treatment, and reduced nitrate leaching by 93% while increasing the water use efficiency by 75% compared to a fixed 2-h irrigation event per day treatment. Application of N above the standard recommended rate of 145 kg ha⁻¹ did not increase yield, although yields were reduced at the lowest N-rate. The use of soil moisture sensors for automatic irrigation control reduced irrigation application and minimized nitrogen leaching. In addition, combining the soil moisture controlled SDI system that had surface applied fertigation resulted in similar or higher yields, while reducing both water use and potential N leaching because of improved nutrient retention in the root zone.     

Soil Disinfestation with Steam: A Review of Economics,Engineering, and Soil Pest Control in California Strawberry

ABSTRACT

Increasingly stricter fumigant regulations will limit their use and require effective non-fumigant treatments if large-scale strawberry production is to continue in California. Steam has long been used for soil disinfestation in greenhouse soils where it controls most soil pests. The challenge of field-scale soil disinfestation with steam in place of fumigants is availability of machinery capable of treating a large acreage in a timely manner while making the most efficient use of fuel and water. Steam can be a component within an integrated set of fumigant and non-fumigant practices. Steam used together with other practices may permit technically and economically sustainable strawberry production into the future by allowing growers to adapt to more stringent fumigant use restrictions. It may be possible to overcome some of the limitations of steam because steam generator technology has advanced in recent years as well as recent developments in co-applications with steam, including exothermic compounds co-applied with steam and mustard seed meal co-applied with steam. Regarding steam generator technology, direct-fire steam generators are more energy efficient than traditional steam boilers and avoid the hazards of steam pressure vessels. Steam is arguably the most effective non-fumigant method of soil disinfestation and it likely has a role in a future California strawberry production system that is forced to use much less fumigant than it does at present.     

巨大口蘑出菇期耗水量与产量的关系

研究了巨大口蘑不同出菇时间培养料的失重和含水量变化，及其不同补水量对产量的影响。结果表明，出菇20d时，菌袋失重最大；随着出菇时间的增加，培养料的水分含量逐渐减少；出菇过程中不断补水有利于子实体生长，补水量40g·袋-1-45g·袋-1时，总产量提高26．9％。     

袋栽金针菇2潮后脱袋增产技术研究

为满足商品性要求,袋栽金针菇2潮后一般不再进行出菇管理。实际上,这时的菌棒仍有出菇趋势,由于塑料皮限制其生长,且阻碍补水补养,致使无法产生商品性好的菇,培养基中养分无法利用充分。试验中割破塑料皮,采用脱袋排场盖膜法和脱袋拱棚盖膜法进行继续出菇管理,并设置对照。结果表明,2种措施可分别再出菇3潮,生物学效率分别提高34％和28％,商品性满足三级以上标准,是可推广的金针菇增产措施。     

Influence of the water potential of the casing soil on crop yield and on dry-matter content,osmotic potential and mannitol content of the fruit bodies of Agaricus bisporus

In the culture of the mushroom, Agaricus bisporus, significant amounts of water are taken up from the casing soil. The water potential of the casing soil was lowered by adding sodium chloride. A lowering of the water potential reduced crop yield, slowed fruit-body development and increased the dry-matter content of sporophores as a percentage of wet weight. Values for dry-matter content of the fruit bodies ranged from 6.7 to 11.5%. Regulation of dry-matter content is therefore possible by adjusting the concentration of salt in the casing soil. The total dry weight of all harvested fruit bodies of the first two flushes (breaks) from cultures with a low water potential in the casing soil (high salt) was as high as that of the crop of cultures with a high water potential (no salt added). The total concentration of osmotically active substances in the pressed juice of caps of fruit bodies increased with decreasing water potential of the casing soil. The increase in mannitol concentration of the press juice contributed significantly to this increase. A positive correlation was found between the concentration of osmotically active substances in the pressed juice and the increase in dry-water content of fruit bodies. Mechanisms of water uptake and movement from the casing soil to the growing fruit bodies are discussed.     

Effect of salinity and water table on growth and tolerance of plum and peach

The effects of combinations of salinity (no salt, 2000 p.p.m. or 4000 p.p.m. of CaCl₂ and NaCl, 1:1) and water table (30 cm, 60 cm or 90 cm from the soil surface), on the vegetative growth and tolerance of ‘Golden Japanese’ plum and ‘Mit Ghamre’ and ‘Balady’ peaches were studied. The plants were grown in lysimeters. The growth of the trunk, total shoot length, the increase in shoot length per cm and the fresh weight of top, root and total plant were reduced with increasing salinity of the irrigation water. The effect was accentuated when the plants were maintained at high water table level. The salinity treatments resulted in the death of 43%, 73% and 76% of the plants in the plum, and the ‘Mit Ghamre’ and ‘Balady’ peaches, respectively, indicating that the plum is more tolerant to salinity than the peach. The plants of the salinity treatments showed various symptoms of salt injury, such as leaf burn, defoliation, shoot die-back and finally death. In the peaches, salt injury started to occur in the first growing-season, whereas the salt injury appeared in the plum in the second growing-season. The symptoms were more pronounced in the 4000 p.p.m. treatment than in the 2000 p.p.m. treatment and were more pronounced at the high water table level. The salinity level was the predominant factor and the effect of the water table on the vegetative growth diminished with increase in the salinity level of the irrigation water.