© 2014 Holdeks Group B.V.
Design by ORLY






CULTIVATION

1.CO2 system
Main objective to the Greenhouse Heating / CO2 system is to contribute to year round optimal climate necessary for efficient production of greenhouse crop. CO2 is one of the most important elements to raise produce quantity and quality of the crops. The goal of CO2 dosing is to achieve the higher photosynthesis efficiency. CO2 originates from the combustion of hydrocarbons such as natural gas. The generation of heat doen with boilers with natural gas. That is why CO2 is a cheap by-product when heat is required in the greenhouses.
2.Assimilation lighting
Assimilation lighting increases the rate of growth and the quality of the crop. Additional light provides better control of the production process. Optimal assimilation lightning requires a right balance of many factors. Fixtures, reflectors. the pattern the distance of the lamps and the crop must be optimally geared to another.
3.Water quality requirements for heating system
3.1.Filling water of the heating system
The filling water of the heating installations has to be checked by the customer prior to the filling of the installations in order to take direct action with possible required water treatment. Water treatment and inquiry costs are excluded from our order / quotation unless stated otherwise. For filling of the heating systems there are four possibilities which are discussed below.
3.1.1.Filling with softened drinking water
Filling of the heating system with softened drinking water is the most preferable option. For softening of the water a water softening installation is required. It is possible to dose supplemental water treatment by means of a dosing pump along with the softening process.
3.1.2.Filling with rain water (from rain water pond)
When heating system is filled with rain water from the rain water pond, the pH value of the water is often to low (approximately 4.0). An alkaline water treatment product has to be applied (lye). It is advisable to filter the water because of pollutions of the water with sand and leafs.
3.1.3.Filling with spring water
Spring water can contain high concentrations of iron and manganese. First the water has to be de-ionized (magneting). After this process softening of the water may be necessary. With iron elements in the water always apply a part flow filter with a magnet.
3.1.4.Filling with surface water
Heating installation never fill with surface water because of existence of pollutions such as sand, clay, mud, slit or organic pollutions (microbiology). Application of surface water is for full risk of the customer.
Note: Application of water treatment depends on system configuration. Which are for example water quality, water content, heating temperatures, material usage, application of heat storage tanks, CHP systems, closed of open systems, application of many PE hoses in the system.
3.2.Water analyses
3.2.1.Taking water samples
Taking water samples has to be executed in competent way. Otherwise the water analysis may result in a distorted conclusion. Water samples have to be taken in with clean sealable containers. Prior to sample the containers has to be can flushed thorough (3 times) with the sample water.
3.2.2.Water sample analyses
The analysis of the water sample has to be executed within two days to prevent deviations in the results.
3.2.3.Water sample frequency
The single water sample prior to filling of the installation is not a guarantee for the water quality of the heating system over the long term. It is advisable to analyze the water quality on a regular basis. Definitely when water is added to the system. Only in this way a good image can be formed with regards to the water quality.
3.3.Required parameters of water for heating system
These are the recommend limits for greenhouse heating system WITHOUT aluminum! General the visual state of the water has to be clear and odourless, free of sediments and airborne particles.
Parameter Units Recommended limits
1 Colour clear
2 Suspended material none
3 pH 9,5 - 10,0
4 Conductivity µS/cm < 1000
5 Total hardness dH < 0,1
6 Bicarbonate hardness dH
7 P-alkalinity mVal/l 0,5 - 2,0
8 M-alkalinity mVal/l
9 Bicarbonate mg HCO3/l
10 Sodium mg Na/l
11 Potasium mg K/l
12 Chloride mg Cl/l < 100
13 Sulphate mg SO4/l
14 Ammonia mg NH3/l < 0,5
15 Nitrite mg NO2/l < 1,0
16 Nitrate mg NO3/l < 5,0
17 Phosphate mg PO4/l 10 - 30
18 Sulphite mg SO3/l
19 Silica mg SiO2/l
20 Iron mg Fe/l < 0,5
21 Molybdate mg Mo/l
22 Dissolved oxygen mg O2/l
23 Aluminium mg Al/l < 0,1
24 Copper mg Cu/l < 0,1
25 Smell none
4.Water quality requirements for irrigation system
4.1.Irrigation water quality “Main elements”
The water quality is depends on the total salt content, measured as EC, the sodium and chlorine concentration, the pH and the bicarbonate concentration. The other elements which are often found in water like calcium, magnesium and sulphate are in most cases useful as a feeding element. The influence of every element will be explained.
4.1.1.pH and bicarbonate
The optimum pH of feeding water is around 5.5. The pH depends on the amount of bicarbonate. A concentration of 0.5 mmol bicarbonate /l is useful as buffer. Higher bicarbonate concentrations have to be reduced by adding acid. For every mmol bicarbonate an equal amount of acid has to be added. When the feeding solution is calculated also the amount of acid is calculated. The amount of acid is calculated for 100,000 litre and is only valid at the EC that is present in the AB tank. In case the EC of the feeding water is increased than relative too much acid is added. In case the EC is decreased than relative too low amounts of acid are used. So in case acid is used be care full and ask Dalsem to make a recipe calculated at the right EC. This because changing the EC also influences the relative amount of acid per litre. Precipitation can occur when the amount of bicarbonate is 2 times higher than the amount of calcium and magnesium together.
4.1.2.The EC
The salt content of water is measured as conductivity in milli siemens per cm (mS/cm). The EC gives only the amount of salt ions, which ions are in the water is unknown. The EC in rain water is low, around 0.1, in surface water mostly between 0.5 and 1.5 and in well water the EC can be low but can also go up till above 2.0mS/cm. The salt tolerance depends on the crop and the way of watering, overhead, drip or recirculation. For this reason the table gives a general overview.
Quality indication of basic water for optimal growth
EC [mS/cm] Na [mmol/l] Cl [mmol/l]
Good < 0.5 < 1.5 < 1.5
Acceptable 0.5-1.0 1.5-3.0 1.5-3.0
Bad > 1.0 > 3.0 > 3.0
4.1.3.Sodium and chlorine
Both elements increase the EC and are not necessary for the plant. The standard EC is higher so less good elements can be dissolved in the feeding solution. Sodium and potassium are both easily taken up by the plant so at higher sodium concentrations the uptake of potassium is lower. For this reason the dosage of potassium is increased in the feeding water, for every 2 mmol Na, 0.5 mmol K extra. Sodium is easily taken up and the excess accumulates in the leave tips and edges. Finally the tips and leaf edges become necrotic and die. The uptake of chlorine is less harmful and plants can take up quite a lot of this element. A tomato plants has no problem with 10 μmol chlorine in the feeding water. The chlorine can even enhance the uptake of calcium.
4.1.4Calcium, magnesium and sulphate
These elements are normally present in surface and well water. As long as the concentration is lower than the concentration wanted in the feeding solution the elements are useful. In case the concentration of the elements is higher than the concentration wanted in the feeding solution it is an excess. A higher concentration means a higher EC and the large amounts of cat ions cause antagonistic effect against other elements. In case of higher concentrations of sulphate and calcium a precipitate occurs on the leaves of the plant. This is caused by the formation of lime.
Quality indication of feeding water
Ca Mg S [mmol /l]
Good < 2 < 0.5 < 0.5
Acceptable 2-4 0.5-2.0 0.5-1.5
Bad 4-6 > 2.0 > 1.5
4.1.5Conclusion
Surface or well water is useful in case the concentration of the elements is not too high. Dalsem always advises to take a sample from the basic water. Only when it is known which elements are present in the basic water a good feeding solution and advice can be made for
Summary
• High pH; bad growth, caused by less uptake of phosphate and iron
• High EC; salt damage, yellow leaves
• High Na; potassium deficiency
• High Ca and HCO3 -; precipitation of lime
4.2.Irrigation water quality “Microelements”
These elements cause by excess often a lot of damage. Well water often contains iron, manganese and boron, surface water a lot of boron. These elements have to be reduced from the feeding solution. Iron is an exception because the iron from well and surface water is not easily taken up.
4.2.1.Iron
Some soils contain a lot of iron. The well water also contains a lot of iron and when reaching the surface the iron is oxidizing. The oxidized iron precipitates and this is visible as red iron. In case not all iron is removed precipitation can occur in drippers and on the leaves of the plants. When drippers are used the iron concentration should be lower than 10 μmol/l. The iron concentration may be a bit higher in case the water contains a lot of organic matter. Water with a concentration of 25 tot 50μmol iron can be used whit overhead raining on green and outside plants. Higher concentrations of iron are possible when water is given on the soil and the water is not coming in contact with the plants. In general no damage is seen when concentrations are below 100μmol/l. Aeration of well water will precipitate most of the iron. In case the iron content stays too high professional equipment is necessary.
4.2.2.Manganese
Well water can contain high amounts of manganese. This is not directly damaging the plants because most manganese will precipitate in the soil. The problem is that with decreasing pH the manganese comes into solution and is taken up by the plant. Concentration above 10-20μmol/l can cause damage.
4.2.3.Zinc
Tubes, tanks and greenhouse constructions containing zinc are often a source of zinc. Zinc concentration above 5 till 10μmol in the water should be avoided.
4.2.4.Boron
Well water and surface water often contain large amounts of boron. Boron is easily rinsed out but can increase in closed systems. Concentrations in the range of 15-50μmol are in most cases acceptable. Up till 100μmol is sometimes possible. Glass bottles contaminate a sample with boron out of the glass and should not be used.
4.2.5.Copper
The plant only needs small amounts of copper. Watering systems sometimes contain copper valves and in combination with acid the copper slowly dissolves and in this way contaminate the water.
4.2.6.Fluor
Bulbs, tuber crops and palms are sensitive for Fluor. The maximum concentration for sensitive crops is set at 25μmol/l, in other crops the maximum concentration is set at 50μmol/l. Fluor is used for cleaning glass greenhouses and this water can reach the surface water. In case surface water is used for watering the concentration fluor can increase unknown.
4.2.7Contamination of water samples with micro elements
Water that has been standing still in metal tanks can contain more zinc or copper. For the same reason it is important when tanking a water sample to let the tap flow for 15 minutes to get fresh water. Always be aware of contamination of the water.
Summary
Maximum concentration micro elements in basic water:
Element Concentration
Iron < 10 μmol
Manganese < 5 μmol
Zinc < 3 - 5 μmol
Boron < 7 - 25 μmol
Copper < 0.5 μmol
Fluor < 25 or <50 μmol