Build Your Own Greenhouse

Tiberian Growdome System

Are you tired of dealing with so-called organic foods or or vegetables that you know are covered in lethal chemicals? If you are, why not grow your own food? It is not nearly as hard as people make it out to be Growing your own food is one of the most rewarding things that you can do! You are being healthy in two ways; you're growing all-natural foods AND you're staying fit by growing food! This ebook teaches you how to make a simple device from ancient times that allows you to grow the very best food that you can at home! This device is much like a small greenhouse You will be able to control the climate inside to make sure that your plants are always in great weather. Don't go along with the rapidly expanding food prices; start growing your own, and don't play the game of people that want to hurt the food supply with chemicals and genetic engineering! Read more...

Tiberian Growdome System Summary

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Building A Greenhouse

The eBook Building A Greenhouse contains full color step-by-step scale plans. Learn how to build a good sized, sturdy and attractive Victorian style greenhouse perfect for a backyard garden or for you own small organic vegetable and fruit farm. With easy to follow cross-sectional diagrams that include exact dimensions and required materials. Learn the importance of ventilation and what type of ventilation system you'll require whether it be vents, doors or exhaust fans. Discover the essential conditions, including temperature, lighting and soil, you must have to grow your own herbs. Learn how to build a medium sized lean-to greenhouse that you can easily fit against any existing wall to save on space and materials. Discover if and why you need shading and what materials make the best shading and how your should apply it to your greenhouse. Learn how to build a large hoop or arch greenhouse out of Pvc piping and save a bucket load of money. How to build a small greenhouse grow rack that you can fit in even the smallest of backyards.

Building A Greenhouse Summary

Contents: Plans, Ebook
Author: Bill Keene
Official Website: www.buildingagreenhouseplans.com
Price: $37.00

Development of Greenhouse Horticulture

Last decades of the 20th century the greenhouse horticulture in high technological developed countries is characterized by a rapid changing technology with a degree innovative power. The technological applications were not solely directed on extension and higher productions, but primarily on the sustainability of the greenhouse industry. In this development main focuses were quality improvement of the produce and strong reductions on the environmental impact. With respect to last item, three subjects accompanied the research in the greenhouse industry reduction of the use of energy, reduction of the use of plant protection chemicals and reduction of the emission of minerals, focussed on N and P. Solutions in these directions were found in high technological developments, like for example increasing yields, storage of energy over seasons, use of residual heat, co-generation of electricity, biological control of pests and diseases, and reuse of drainage water for substrate grown crops....

Organic Matter and Physical Characteristics of Greenhouse Soils

The physical characteristics of soils are mostly not a restriction for the employment of protected cultivation. In The Netherlands for example greenhouse industry is situated on very different soil types. In a series of 75 soil samples from greenhouses in The Netherlands the mass fraction organic matter of oven dried soils varied between 0.03 and 0.61, while the mass fraction clay (particles < 0.002 mm) varied between 0.03 and 0.40 (Sonneveld et al., 1990). Furthermore, a relatively high salt content, mostly in combination with a high content of soluble Ca keeps the soil in a crumbly and flaky condition (Hilgard, 1919). The intensive tillage stimulates a loose structure further on. Therefore, the bulk densities of greenhouse soils mostly are lower than those of field soils. Between the fraction organic matter, determined by loss on ignition and the bulk density of greenhouse soils exists a closely relationship, like shown in Fig. 2.3 (Sonneveld, 1990). The characteristics of the...

Fertilization in Greenhouse Industry

In contrary of many other agricultural activities the costs of fertilization in the greenhouse industry are relatively low and amount to only a few percentages of the total costs. Thus, from economic view points were no arguments for a precise and careful application of plant nutrients. In the past an abundant use of fertilizers in the greenhouse industry was common practice and there was no interest by the growers to limitations in the use of fertilizers to prevent in this way the leaching of nutrients to the environment. However, in the last decades of the 20 th century environmental pollution became a subject of permanent attention by the governments of North-West European countries and was quickly followed by regulations from the European Community. Measurements by the Dutch greenhouse cultivation learned that substantial quantities of nutrients can be transported to the deep ground water or surrounding surface water like ditches, canals and rivers. In Table 1.1 some data is...

Greenhouse Soils In Situ

For a wide range of soil types Van den Ende (1988a) found a close linear relationship between the water content of greenhouse soils cultivated with tomatoes and the water content at a pressure head of -6.3 kPa, as shown with formula (3.3). Thus, the water contents of the greenhouse soils grown with tomato were more or less equal to that at a pressure head of - 6.3 kPa. Sonneveld et al. (1990) also determined the relationship between the loss on ignition and the water content under growing conditions and found a comparable relationship for a series of 75 greenhouse soil samples. These samples were gathered from greenhouses with different crops, merely during the cultivation period. The mass fraction organic matter and clay of the soils varied from 0.03-0.61 and 0.03-0.40, respectively. The relationship is shown in Fig. 3.3, and the equation found is given in formula (3.5). Both formulae resulted in comparable values over a wide range of soil types. Thus, on basis of these formulae the...

Water Uptake by Plants

Water uptake by plants in greenhouses is entirely studied by Stanghellini (1987). In this study it was concluded that the transpiration rate is almost proportional to the leaf area and that in the greenhouse climate the radiation, the ambient temperature and the humidity play a prominent part. To a minor extent the temperature of the greenhouse cover and of the soil surface also play a part. On basis of the factors affecting the water absorption of plants, models have been developed with simple and quickly measurable parameters. The stipulation that the parameters should be simple and quickly measurable is suggested by a practical suitability to irrigate on basis of the everyday water absorption of the crop. Nowadays, when many crops are grown in substrate systems, these requirements on the parameters are accentuated, because of the small water storage in the root environment of these systems and the need to keep this storage on a reasonable level. In such systems often water is...

Accuracy of Soil Testing

In The Netherlands research has been carried out to estimate the size of the errors with soil testing in greenhouses (Sonneveld, 1979). To this purpose some hundreds of greenhouse soils were sampled in duplicate and the samples were analysed also in duplicate at the laboratory. With these results besides the total error also the sampling error and the laboratory error could be estimated separately. The standard deviation was used as a measure for the errors.

Breeding Is Inherently Inefficient

Selecting for phytochemical content also requires extraction and analysis of the phytochemical from tissue samples from every plant of the population. High throughput technology makes this feasible, but in many instances, greenhouses or suitable land and labor needed to grow large numbers of plants may not be available. It is well documented that metabolic pathways are controlled by multiple genes, and therefore, phytochemical content is influenced by the environment, genotype, tissue, and maturity of the plant. For example, Prior et al., (1998) found an increase in phe-nolics and anthocyanins of blueberries with plant maturity. Isoflavone content in soybean seeds was shown to vary with environment and variety (Eldridge and Kwolek, 1983 Tsukamoto, 1995). Breeders over the past 50 years have focused mainly on improving protein quantity and quality of staple foods, so information is largely lacking on the effects that agronomic practices, climate, and soil have on phyto-chemical levels....

Ammonium Phosphates N

Ammonium phosphates are important phosphorus-containing fertilizers because of their high concentrations of phosphorus and water solubility. Diammonium phosphate (commonly 18 N, 46 P2O5) is a dry granular or crystalline material. It is a soil-acidifying fertilizer and is useful on calcareous soils. It should be incorporated into the soil. It is a common starter fertilizer and is a common component of greenhouse and household fertilizers. Monoammonium phosphate (commonly 11 N, 48 P2O5) has uses similar to those of diammonium phosphate. Ammonium polyphosphate (10 N, 34 P2O5) is marketed as a solution. Its use is similar to that of monoammonium phosphate and diammo-nium phosphate. Ammonium phosphates are made by reaction of ammonia with orthophosphoric acid (mono- and diammonium salts) or with superphosphoric (pyrophosphoric) acid (152).

Water Extracts Based on Weight Ratios

For routine testing of greenhouse soils formerly often use was made of different weight ratios of water to air dried soil. To this purpose ratios of 1 1, 1 2 and 1 5 are practised (Carpena et al., 1968 Van den Ende, 19688). Nowadays there is not much reason to practice them. The water to soil ratio in the suspension has no relationship with the water contents of soils under growing conditions, when used for different soil types. Therefore, the analytical data need adjustment to this water content to get an interpretation related to the chemical composition of the soil solution (Van den Ende, 1989b). Fig. 4.1 Percentages of cations in soil solution, saturation extract and 1 5 w w water extract calculated over average values of 75 greenhouse samples. After Van den Ende (1989b) cations increase and bivalent cations decrease relatively with increasing dilution (Moss, 1963). The effects of this called dilution and valence effect of different dilutions with soil testing of greenhouse soils...

Distribution of Minerals Within Plants

This way, the differences in Ca concentrations found within a tomato plant by Adams (1990) varied between 1 and 600 mmol kg-1 in the dry matter of the distal ends of fruits and of the laminae of young leaves, respectively. The differences should even be more striking when the comparison was made with old leaves, because the Ca concentrations in old leaves can be double of those in young leaves. Differences in mineral concentrations between young and old leaves are shown by Sonneveld (1980) and summarized in Table 5.1. The most striking differences are the lower the low K and N and the high Ca and Mg concentrations in the old leaves in comparison with the young leaves. The unequal distribution of Ca among plant tissues, as brought about by the internal water transport processes, easily induces deficiency symptoms in therefore susceptible plant organs. Formerly, these phenomena often were denoted as physiological disorders and are well known with many crops in greenhouse cultivation....

Variations of Uptake and Supply

Many different irrigation systems are available in the greenhouse industry. They can Systems due to spot or strip irrigation, like drip irrigation systems and mini sprinklers. This group is characterized by local wet spots or strips in the greenhouse where the water is supplied, while the remaining part of the surface stays dry. The crop is not wetted during irrigation (Van den Ende and De Graaf, 1974). Systems with which the whole area of the greenhouse is irrigated, like with high level sprinkler irrigation, see Picture 6.1. The spray lines with nozzles are placed in top of the greenhouse. The whole greenhouse area and also the crop canopy are wetted with any irrigation. The water uptake among individual plants varies strongly, as well as the local water supply of irrigation systems. This has been shown by studies of Van der Burg and Hamaker (1987) and of Van Schie et al. (1982) for drip irrigation systems. In the study of Van der Burg and Hamaker (1987) the water supply and the...

Specific by Volume Water Extract

Soil Extraction Sonneveld

The specific 1 2 by volume extract, henceforth called 1 2 extract, is prepared by filtration of a suspension obtained by adding sufficient field-moist soil to two volume parts of water so that the total volume is increased with one part (Sonneveld et al., 1990), see picture 4.1. When the soil is too dry, before the preparation of the extract some demineralised water will be added to the soil to restore field moist condition. The field moist condition of greenhouse soils is defined in Section 3.3 and agrees with the moisture content at a pressure head of -6.3 kPa. In advance this judgement should be compared with results of the sandbox method, but after some experience the judgement can be carried out visually. The suspension is shaken for 20 minutes. The method is exclusively recommended for greenhouse soils. For a detailed description of the preparation of 1 2 extracts reference is made to De Kreij et al. (2005). Table 4.1 Regression equations for the relationships between EC and...

Osmotic Potentials of Soil Solutions

In Table 3.1 the composition of soil solutions from field soils is given in comparison with those from greenhouse industry. In the comparison soil solutions as well as substrate solutions are taken into account. The most striking difference between the solutions derived from fields soils and those from greenhouses soils are the overall much higher nutrient concentrations in solutions from greenhouse. This especially holds for greenhouse soils where the EC in the solution is highest. Furthermore, it is obvious that in greenhouse cultivation nutrients contribute substantially to the total salt concentrations of soil and substrate solutions and thus to the osmotic potential. Table 3.1 Ionic compositions of soil solutions. Ions expressed as mmol l 1 and EC as dS m 1. The no's 1-5 are from field soils and the no's 6-9 from greenhouses Table 3.1 Ionic compositions of soil solutions. Ions expressed as mmol l 1 and EC as dS m 1. The no's 1-5 are from field soils and the no's 6-9 from...

Fertilization Programmes

In the past fertilization and irrigation in greenhouses was based on the experiences of growers. The addition of farm yard manure and other natural organic products was common practice, supplemented with fertilizers used for field crops. Often these fertilizers contained high NaCl contents. Formerly, this was mostly not a problem for field crops, because of the surplus of the precipitation in winter, by which the salt residues were leached from the root zone. However, since the natural precipitation was excluded by the greenhouse constructions salts could easily accumulate in the greenhouse soils to levels that reduced the growth of many crops. The salts accumulated during cultivation, especially in the top layers in the greenhouse soils, like shown in Table 1.3 (Van den Ende, 1952). The high salt content in the top layer at the end of the cropping period was a major hindrance for the start of a new crop. Therefore, such soils must be flooded before a new crop could be started. The...

Symptoms of Nutrient Disorders

Symptoms of nutrient disorders in greenhouse crops do not differ in principle from those in field crops. Most of the characteristics of nutrient disorders found with field crops also occur in greenhouse crops. So there is no reason for an extended description of these symptoms. However, the specific climatic conditions in greenhouses sometimes induce symptoms accompanied by specific characteristics. Therefore, a short description will be given of the most characteristic symptoms of the nutrient disorders with possible relation to greenhouse conditions. The symptoms differ for crops, growing conditions and growth stage and often cannot unambiguously be described. Sometimes a diagnosis requires comparison of different descriptions and pictures of several crops to make good supposition and even then a tissue test can be necessary to confirm the diagnosis. Especially the diagnosis for the innumerable exotic flower crops grown in greenhouses offers problems in the recognition of nutrient...

Changes in the Chemical Composition

Fig. 3.4 The course of the cation contents as determined in the saturation extract in a greenhouse during a tomato cropping. The soil type was a sandy soil with 5 organic matter Fig. 3.4 The course of the cation contents as determined in the saturation extract in a greenhouse during a tomato cropping. The soil type was a sandy soil with 5 organic matter week 8, the concentrations gradually decreased and the top dressing by fertigation started around week 14. Until the end of the cropping period at week 32, by ferti-gation 300 kg K and 35 kg Mg per ha was supplied. In the greenhouse concerned, water and fertilizers were supplied by sprinkler irrigation and the soil was sampled over a depth of 25 cm. The Na concentration is relatively high during the whole growing period, as a result of the high concentration of this ion in the irrigation water used. Fig. 3.5 The course of the EC and the anion concentrations of the saturation extract in a greenhouse during a gerbera cropping. The soil...

Improvement Of Echinacea Quality

Wild populations of Echinacea provide further scope for genetic improvement. Our greenhouse investigations of E. angustifolia populations grown from seed collected at nine locations on the Great Plains showed a latitudinal variation in the amounts of several phytochemical markers (Binns unpublished). Echinacoside, for example, increases significantly with latitude, while several alkamides decrease as latitude increases.

Soil Solution and Uptake of Micro Nutrients

The quantities of micro nutrients in soil solutions are small in comparison with those found for major nutrients. In Table 3.6 average concentrations of micro nutrients are shown as has been found in greenhouse soil solutions (Sonneveld and De Bes, 1986) and in substrate solutions of rock wool (Sonneveld and Van Voorthuizen, 1988). The concentrations in the different growing media are of the same order of magnitude. Greatest difference has been found for Fe, which will be explained by the use of chelates in solutions used with rock wool substrates. Such complexes are used to Table 3.6 Micronutrient concentrations as has been found in soil solutions of greenhouses (Sonneveld and De Bes, 1986) and in substrate solutions of rock wool (Sonneveld and Voorthuyzen, 1988). Average values of 75 and 90 Dutch sites respectively. Concentrations given as mol l-1 Table 3.6 Micronutrient concentrations as has been found in soil solutions of greenhouses (Sonneveld and De Bes, 1986) and in substrate...

Please Dont Eat the Daffodils

Some are poisonous even edible flowers may be contaminated by chemicals if they weren't grown for eating. Don't eat flowers you buy from a florist or a greenhouse-or that you pick along the road. Don't use them as a garnish, either. There's a long list of flowers that aren't edible buttercup, delphinium, lily of the valley, foxglove, goldenseal, periwinkle, oleander, sweet pea-and daffodils, to name just a few

Soil and Substrate Solution

For substrates, however, the so called substrate solution is often used for routine testing of substrates. This especially is the case for substrates with high water contents at a high pressure head, like mineral fibres and foams (Sonneveld, 1995). During cultivation the crops are irrigated frequently in such substrates, sometimes dozens of times a day, which ensures a stable and high water content in the substrate. Under such conditions the substrate solution easily can be gathered, withdrawing it from the substrate by suction with the aid of a simple syringe. Also with peaty substrates the use of substrate solution is sometimes practiced, because the substrate solution at a pressure head of -1 kP, defined as the moisture condition at field capacity, can be easily pressed out. The method is applied with samples gathered from the greenhouse during cultivation. Before the sample is pressed a careful check on the right moisture condition is required, as well an adjustment with...

Kfertilizers

K fertilizers are listed in Table 2.3. For broadcasting with base dressings mostly the SO4 salt is used. KCl is never used for soil grown crops in greenhouses. It is only used for special applications in substrate cultures, as a replacement for NO3 when Cl is required in the nutrient solution and the concentration in the primary water is very low. To this purpose a very pure form is desired, because the Na content must be very low. Table 2.3 K fertilizers used in greenhouse industry Table 2.3 K fertilizers used in greenhouse industry

P fertilizers

The P fertilizers used in greenhouses primarily consist of orthophosphates. The cheapest and most widely used forms are the Ca salts, from which only the mono form has a high solubility. The low concentrated fertilizers of this form contain a lot of gypsum and therefore, are seldom used in greenhouses. Calcium orthophosphates are never used for fertigation and substrate cultures, because these fertilizers mostly contain too much insoluble components. For greenhouse industry suitable P fertilizers are listed in Table 2.2. Most P fertilizers contain F, which is toxic to some mono-cotyledon plants, especially many bulb and tuber crops, from which freesia is the most well known greenhouse crop (Roorda van Eysinga, 1974). For crops sensitive to F toxicity P fertilizers with a low content of F are on the market. Di-calcium phosphate (CaHPO4) prepared for cattle feed is such a fertilizer, however, solely suitable for broadcasting. Some other P fertilizers are also produced with a low F...

Soil Improvers

Soil improvers are widely used in greenhouse cultures to stabilize or increase the organic matter content of soils. Therefore, the organic matter is the main constituent of soil improvers. Besides an increased water holding capacity and cation exchange capacity, most soils show an improved structure by the addition of organic matter. The latter, especially is the case with clayey soil types, but also on loamy soils such effects can be expected. On sandy soils the addition of organic matter Soil improvers frequently used in greenhouses are listed in Table 2.9. Beside the organic matter soil improvers often contain substantial quantities of mineral nutrients. Some soil improvers contain much residual salts, which can be a drawback. With the use of such soil improvers the osmotic potential of the soil solution can markedly be decreased which can require extra water supply to wash out the residual salts from the root zone. Only the most common types of soil improvers are mentioned. The...

Contamination

Growth, but the uptake of heavy metals by plants can increase to an unacceptable level in the produce for human consumption. Therefore, governmental regulations have set strict maximum limits for the contents of heavy metals in soil improvers. This especially is the case for different compost types, because it is well known that this material sometimes contains high concentrations heavy metals. The occurrence of these contaminants in composts differs strongly and depends much on the character of the waste left by local industries. Products like sewage sludge and municipal waste compost are well known as materials often contaminated and therefore, are not recommended as a soil improver in greenhouses. Bio waste composts and green composts commonly contain acceptable concentrations of heavy metals and are mostly suitable as a soil improver for greenhouse soils. However, the concentrations will be determined and are bound on limits. A review of the limits as has been set in the...

Conclusion

Overall, the conclusion from available data on the use of natural resources, impacts on wild areas, and pollution is that, on average, the negative environmental impact of meat production by animal husbandry on all dimensions of the environmental problem discussed tends to be much larger than that of its equivalent based on reference-crop (soybean) production. One should, however, keep in mind that, in practice, crop production is, to some extent, dependent on manure production generated by animal husbandry. Moreover, for organic farming, this dependence is overwhelming. Furthermore, as pointed out Section II.A, much agricultural land is unsuitable for cropping, but is fit for sustaining livestock farming. Also, there may be specific cases in which the environmental case against animal meat is not clear-cut at all. This, for instance, is exemplified by a case comparing meat from animals grazing on extensively stocked uncultivated areas with their nutritional equivalent in vegetables...

Other Elements

Other elements mentioned to be essential or beneficial for plant development are Ni, Na, Cl and Co (Marschner, 1995). With Ni and Co insufficient or not any research is carried out in greenhouse industry. It will be expected that at least for soil grown crops Ni and Co are naturally available from soil or from the impurities of fertilizers and soil improvers added. For substrate culture the addition of these elements will be considered, because of the continuous improvements of the purification of the fertilizers used for this growing method and the often total absence of minerals in some of the growing media used. Before application a further study to the necessity of these elements and the concentrations required should be carried out. Na and Cl are abundant available in the biosphere and the essential quantities necessary are on micro nutrient level. In greenhouse horticulture, quantities of Cl higher than those essentially required are recommended (Voogt and Sonneveld, 2004). This...

Exchangeable Cations

Obviously, the determination of exchangeable NH4 is impossible in the NH4Ac extract. However, the determination of exchangeable NH4 in some substrates will be important, in view of the high concentration of this ion that can occur. In such cases instead of NH4Ac an equivalent concentration of BaCl2 is recommended (Kipp et al., 2000). For greenhouse soils NH4Ac is also suitable for the determination of exchangeable cations. However, the determination of it is not obvious for greenhouse soils, because the actual mutual ratios of the cations in the soil solution are of more importance than the total available quantities. Such ratios best can be approximated by water extraction.

Phosphorus

With the water extractions like the saturation extract, the 1 2 volume extract and the 1 11 2 volume extract close relationships were found between the P concentration of these extracts and those of the soil and substrate solutions. Thus, water extraction with a low water to soil and water to substrate ratio is a good method to get informed about the solubility of the P in soil and substrate solutions. However, it mostly does not give a good impression about the total available P and even less about the total storages in soils and substrates. This is clear from the data shown in Fig. 4.2, where the quantities of P extracted with different water to soil ratios of three different soils are shown. The P available in the soil solution, and those extracted with the saturation extract and the 1 2 volume extract is only a small fraction of the total water soluble quantities, extracted by a 1 100 w w extract. Therefore, the determinations of P at low water to soil ratios only gives an...

Mg fertilizers

Mg fertilizers used in greenhouse industry are listed in Table 2.4. Kieserite is the cheapest form of magnesium sulphate, but it is slowly soluble in cold water. Therefore, this fertilizer is solely used for broadcasting applications. Epsom salt is used when prompt dissolution is required, like for example with fertigation and the

Moisture Contents

This especially occurs for field crops grown without artificial irrigation or with low frequency irrigation schedules. In such cases, the moisture withdraw from the root zone between irrigations can be considerable, which for example directly will be reflected by a decrease of the osmotic potential of the soil solution. The fluctuations in greenhouse soils are restricted, because of the high frequency irrigation schedules maintained. This especially is the case in substrate systems, where the irrigation frequency under high transpiration conditions increases up to several times per hour.

Pollution

The compounds referred to in Table 17.3 are involved in a variety of environmental problems. Carbon dioxide is a greenhouse gas, which is translucent to visible light but absorbs infrared radiation coming from the earth. Currently, its rising atmospheric concentrations are thought to be Animal husbandry contributes to global air pollution, and more specifically, increases the atmospheric trace gases that have a greenhouse effect. For greenhouse gases, like carbon dioxide and methane, the yearly increase in atmospheric concentration is currently 0.5 and nearly 0.4 , respectively.45,46 For nitrogen dioxide, the increase is 0.25 year.45,46 As pointed out before, this increase induces an upward pressure on temperature near the earth's surface that, in turn, may lead to climate change. Animal husbandry also makes a small, indirect contribution to the deterioration of the ozone layer associated with the loss of chlorofluorocarbon refrigerants that are used in cooling and freezing animal...

Substrates

Tain considerable quantities organic matter, like peaty substrates, the characteristics of the organic matter differ strongly and show a great variation in water holding capacity. In an investigation with peaty substrates (Sonneveld et al., 1974) a correlation coefficient of 0.809 was found between the mass fraction loss-on-ignition and the ratio moisture solid phase at a pressure head of -3.2 kPa, which is considerably lower than the correlation coefficient found with greenhouse soils. Since then the variation in materials used to produce substrates is strongly increased. The pressure head of -3.2 kPa was chosen as being approximately the moisture content under growing conditions in that period. Later on, the moisture contents of substrates during cultivation became higher.

Water Quality

Na and Cl are the ions often abundantly present in water, but sparingly absorbed by most greenhouse crops. Therefore, these ions often determine the leaching requirements. However, in specific cases other ions, like Ca, Mg or SO4 also can control the need of leaching. In Table 7.13 some examples of the composition of irrigation water are listed in comparison with the uptake concentrations of minerals of two greenhouse crops. Approximate concentrations for irrigation water with which it is possible to grow greenhouse crops without salt accumulation in the root environment are listed by Sonneveld (1993a). A review of such data is presented in Table 6.5. The precise concentrations acceptable for specific crops vary, because of the great differences in the uptake concentrations. For most crops Na is more critical than Cl, because of the lower uptake of this element by most crops. From data presented by Sonneveld (2000) for Na and Cl at low concentrations in...

Micro Nutrients

Micro nutrient fertilizers used in greenhouse cultures are listed in Table 2.6. In this table for many elements the SO4 form is mentioned and best available in trade. However, the Cl as well the NO3 forms of these are suitable too. The accompanying anion is mostly not important, because the quantities added are insignificant compared to the quantities of these ions available in the soil. However, for Fe the accompanying ion is a striking issue. Fe is supplied by so called artificial produced chelates, which are widely used in substrate cultivation as well for soil grown crops. The type of chelate used will be determined by the pH of the soil and the growing medium in which the plant is grown. See also Section 13.4 for more information about Fe chelates. Table 2.6 Micro nutrients fertilizers used in greenhouse industry Table 2.6 Micro nutrients fertilizers used in greenhouse industry

Saturation Extract

The saturation extract has the advantage of a low water to soil ratio, closely related to the water content of soils at field capacity. Thus, the results are only slightly affected by sparingly soluble salts and allow an unequivocal interpretation for a wide range of soil types. The dilution factor, being the water content of the saturated paste to the water content of the field moist soil, varied between 1.8 for mineral soils and 1.5 for soils with a high (30 ) organic matter content in studies with greenhouse soils (Van den Ende, 1988a). In another study a dilution factor of 2.0 was calculated for soils with 5 organic matter and 1.6 for soils high (40 ) in organic matter (Sonneveld et al.,1990). In soil salinity a rule of thumb is used that the salt concentration of the soil solution is twice that of the saturation extract (Maas and Hoffman, 1977). This factor of 2 between the both concentrations is too high for greenhouse soils, as can be derived from Table 4.3, where a factor of...

Interpretation

As already discussed, results of tissue test in greenhouse horticulture are mainly used as a confirmation of nutrient disorders in plants. Incidentally it also is used as a quick test to determine the plant nutrient status to control fertilizer application. However, interpretations of tissue tests are fairly complicated, because they are not unequivocal. Great differences occur between the requirements for optimum production, and for deficient and toxic levels of plant nutrients of different crops, but even for different cultivars of the same crop. Furthermore, the growing conditions of the crop, the growth stage and the plant part sampled will be of great influence on the results of the analytical results and thus, on the interpretation. In Table 5.6 some examples of data of optimum levels are listed for some greenhouse crops as published by De Kreij et al. (1992). The data in this table clearly demonstrate the differences between crops, but the range given for the different elements...

Fertilizers

In this section a review will be given of the fertilizers commonly used in greenhouse horticulture. The choice of the fertilizer types used in greenhouse industry sometimes differs from those for field crops, because of the fact that the choice for field crops is strongly determined by the price of the fertilizer. This scarcely is a factor in the greenhouse industry, because fertilizer costs represent only a minor fraction of the total costs of greenhouse industry. The characteristics on which the choice of fertilizers is based are high solubility and low residual salt contents. Furthermore, many fertilizers in the greenhouse industry are used for fertigation of soil grown crops and substrate cultures and therefore, must be free from insoluble material. Such residues are not harmful to crops, but enhance the clogging of drip irrigation systems used for fertigation. For fertigation with sprinkler systems, the blocking of the nozzles is less a problem, but insoluble residues easily...

Nutrient Uptake

Despite a precise application and an efficient utilization of nutrients in the modern greenhouse industry, the required additions of nutrients will stay high in this horticultural branch. This is related to the high yields usually gained in greenhouses. Between the yield of crops and the uptake of nutrients often a close linear relationship was found, like shown for tomato and chrysanthemum in Fig. 1.1. The relationships shown for both crops differ strongly. This can be explained by several factors, of which are the most important ones the characteristics of the crops, the mutual ratios of the ions in the external solution, the growing period, and the definition of the yield. Greenhouse crops are generally grown at high external nutrient concentrations and realise under these conditions an optimal nutrient status in the plant. A nutrient status in the external solution higher than required does not significantly affect the uptake (Sonneveld and Welles, 2005). However, the mutual...

Sampling

The results of the analytical data of soils and substrates are affected strongly by the method of sampling. The great variation in the chemical properties from spot to spot requires a special procedure to gather a sample that significantly reflects the composition of the soil and the substrate in the greenhouse. Variations in chemical properties of spots in a greenhouse area can be distinguished in systematic and Examples of systematic variations in soils and substrates in the greenhouse industry are for example the distribution of salts and nutrients with the use of drip irrigation in soil grown crops. In Fig. 4.4 the distribution of NO3 between the nozzles of a drip irrigation system is shown. The nozzles were placed near the plants and strong accumulations of salts and nutrients occur in the area between plants. Another example is the vertical distribution of salts shortly after fertilization as shown in Table 4.8. Table 4.8 Vertical distribution of nutrients in greenhouse soils...

N fertilizers

N fertilizers used in greenhouse cultivation contain N as NO3, NH4 or urea. For growing in soil all forms are used, while for substrate growing mainly NO3 is applied and NH4 also in small quantities. Urea is not used in substrate cultivation, because in substrate solutions urea will survive rather long and can be toxic to plants. Sometimes urea is used for pH stabilisation in the water used with drip irrigation of potted plant cultures. In substrate growing NH4 especially is added to nutrient solutions to control the pH, see Section 13.4. On calcareous soils the use of urea as well NH4 is also effective for adjustment of the pH which is discussed in Section 15.7. In Table 2.1 a review is given of the N fertilizers commonly used in greenhouse industry.

Compound Fertilizers

The fertilizer industry produces a lot of different compound fertilizers for soil grown crops, mostly containing guaranteed contents of N, P and K being the elements most widely applied in greenhouse industry. They can be separated in those meant for broadcasting and those suitable for fertigation. Last types often contain beside the elements mentioned, also Mg and micro nutrients. Besides the elements mentioned compound fertilizers mostly contain significant quantities SO4 as a residue. The numbers with which compound fertilizers are characterized are the percentage N P2O5 K2O MgO. There are numerous different compound fertilizers, adjusted to crops and to application methods. The often high P contents are a drawback, because the addition of this element is usually not required by crops grown in soil. Most greenhouse soils contain more than enough P, because of the long term heavy supply of fertilizers and manures (Roorda van Eijsinga, 1971). With single fertilizers the application...

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