Especially during the first and second year of growth it is essential to moisturize the soil regularly. The plants then still have a limited and not very deep reaching root-system and the saline content of the soil is usually higher due to the heavy fertilization that took place before planting.
If plants do not get enough moisture the tips of the young shoots will die off (tip-death). This can also occur after a period of heavy rain because some types of soil will then close off. This will lead to a lack of oxygen in the soil, as a result of which the plant can not absorb water anymore. Tip death can also occur during sudden sharp changes in the weather, when for example a cold, wet period is followed by a very warm and dry period. Try to prevent tip death by supplying moisture regularly. Even though the degree of moisture on the surface may be sufficient the soil underneath may still be very dry. Therefore it is important to check moisture levels regularly, especially on the depth where most of the roots are and where therefore most moisture is withdrawn from the soil. If you come to the conclusion that the soil is too dry, irrigation should take place. The amount of water needed depends on the stage of growth the plants are in. There are differences in irrigation before, during and after the harvest. Before the harvest the soil should be brought to field capacity. During the harvest irrigation should be used only to maintain the beds. For that purpose 5 to 7 millimeters of water per time should be enough. Should the soil be too dry deeper down, then small amounts of water should be given regularly but never more than 10 to 15 millimeters at one time. Ample irrigation will reduce the temperature in the soil too much and that may set the harvest back a few days.
After the harvest, when the leafage is starting to develop, increased irrigation can take place. A growing crop will vaporize about 600 mm of water during one season (under Dutch weather conditions), which is 6000m3 per ha. Especially during dry periods the crop can draw a lot of water from the soil. To prevent major shocks to the soil, it is recommended to give not more than 25 mm of water per time. If irrigation is needed frequently make sure that the water is of good quality. If a brown color appears on the crop after irrigation the quality of the water is poor. Water quality is determined by its pH, iron level, saline content and the presence of organic acids.
Our range of various asparagus offers a solution to almost every commercial grower.
The best asparagus plants will not achieve their full potential without a good cultivation system.
Asparagus plants are susceptible to threat from various pests and diseases. A number of precautionary and protective measures are required in order to achieve maximum production.
Raising the beds
It is difficult to indicate the exact time in spring when the beds have to be raised. If this is done too soon, the ground temperature will still be low. The soil thrown on top of the plant is cold which will delay harvest. Raising the beds too late is problematic too. If too many stems have already started to bud before this takes place, the quality of the first asparagus will be poor. Therefore it is generally considered best to wait until some of the stems have started to bud. On wetter and colder soil it is better to raise the beds in two times. If anti-condensation polythene is used the beds should be raised as soon as possible and the polythene should be placed in position at once. While raising the beds make sure that as little damage as possible is done to the roots. Therefore the discs of the mounted asparagus plough should be made fairly broad so that soil is taken away more broadly and it is not taken too deeply from the root layer. Every bed should be raised to about 35 cm over the crown. When the soil sinks down, 30 to 32 cm will remain. The beds must not be firmed too much, either at the top or on the sides, because that leads to too many crooked stems which makes harvesting more difficult. Plowing should be done in a straight line, so that the plants are in the middle of the bed. Do not raise beds when the soil is very dry because then the beds will not hold. Furthermore dry soil is a poor heat conductor and production will start very slowly. Depending on the weather conditions the beds may have to be raised several times during one season.
Plowing down the beds or not?
After the harvest the remaining stems should be allowed to grow out as quickly as possible. That will give them the chance to store energy for the next year. In the past this was speeded up by plowing down the beds. But in that way many stems are damaged. Damaged stems do not grow properly and they slow down the development of new stems. Also a considerable loss of production will occur. One stem less per plant means 700 to 1000 kg of asparagus less per ha.. There are two methods that can be used without damaging the stems. The first method involves partial plowing down of the bed. By changing the position of the discs the soil is worked to the sides, leaving intact a layer of 25 centimeters on top of the rows. If more soil is removed this increases the risk of damage. The remaining part of the bed is also needed to give enough support to the stems. If this method is followed a chemical weedkiller needs to be used after the beds have been plowed down. Most soils do better if the second method is used: not plowing down the beds. A chemical weedkiller is applied immediately when the harvest is over. More and more growers have started to use this method. Therefore you see more and more growers ending the harvest when the weather is warm so that the stems are able to grow out more quickly.
When winter comes, the leafage needs to be removed. Because fungal diseases such as Botrytis, asparagus rust and Stemphilium have increased over the last few years and because removing the old leafage growth leads to a production increase we recommend removing the leafage, also in older fields. Cut the leafage 10 centimeters over the top of the plant, collect them and take them away or burn them on the spot in small heaps. Cutting should be done with a knife attached to the tractor at an angle of 45 degrees. Attach some strips to the knife so that the fern is loosened more.
Alternatively a milling cutter can be used to mix the leafage into the bed if burning it is no longer allowed.
An asparagus crop forms a lot of stems during the summer and it will then have a large evaporating surface.
Much water is needed to ensure optimal growth to a crop that evaporates a lot of water. Moisture deficiency can be caused not only by dry soil but also by heavy fertilization after the harvest. Too much fertilization can lead to a saline content that is too high. Then the plant has trouble absorbing water and it will dry out sooner.
Here is some advice as to fertilization. In autumn, after the leafage has been removed, the field can be fertilized with 25 to 35m3 of organic manure per ha. Organic manure has a beneficial effect on the structure, roots and oxygen supply in the soil. If this fertilization is done in autumn there is no need to use an artificial fertilizer as well. Only on soils which are known to often have a deficiency of magnesium, extra fertilization can take place by using 200 to 300 kg of Kieseriet.(25% Mg) On fields where no use is made of organic manure a week before the end of the harvest 300 kg of NPK (12+10+18) per ha. can be distributed.
An extra 300 kg of Kieseriet per ha. might be added to this.
Asparagus for outdoor cultivation
Laying out 1 hectare of asparagus will soon cost euro 15,000. Its later yield can vary greatly, but is largely determined by the measures taken before planting. Apart from good preparation and careful laying out professional crop care will be needed to ensure maximum produce.
The ten commandments for growing asparagus successfully:
- Start in time with the preparations for a production field.
- Only use suitable soil.
- Apply appropriate deep field preparation.
- Make sure the soil contains enough nutrients.
- Choose the most suitable variety of asparagus.
- Demand planting material of excellent quality.
- Plant carefully and at the right time.
- Make sure that the soil can be kept sufficiently moist.
- Apply appropriate crop protection.
- Harvest on time
Before planting takes place trenches are made of 22 cm deep(for the production of white asparagus) or 10 cm deep (for the production of green asparagus). The distance between rows should be somewhere between 1.7 mtr and 2 mtr, depending on the size of the available machinery such as tractors. In some very warm climates a larger distance between rows is to be recommended. In the trench a small mound is made of about 3 cm on which the crowns are spread out.
The buds on the crowns should be placed along the length of the row so that the plants will grow in a straight line. The best distance between the plants in the trenches is 20 cm, depending on selected variety. The crowns should be covered immediately with about 8 cm of soil. Nowadays also double row systems are applied. In that case the crowns are planted on both sides of the trench. The distance between the rows is in this case somewhat wider , eg 2,25 mtr up to 3 mtr. If the crowns have been disinfected they should be planted before the sun can dry them up. If the weather is dry it is beneficial to irrigate the crowns. During the summer the trench is gradually filled in as shoots emerge. Weed control also takes place. Finally a small mound is set up against the new stems, so that in winter when the fern has been removed, the rows can be recovered. Working accurately and creating straight rows can prevent a lot of annoyance. At the moment several machines are available which ensure accurate planting. Perhaps your contractor has such a machine.
Harvest and storage
Asparagus should be harvested once a day, preferably early in the morning because asparagus changes color when it is exposed to light. If the weather is very hot it should be harvested twice a day.
The place where stems are about to emerge can be recognized by a star-shaped crack on the surface of the bed. The stem is then partly dug out and cut off by means of a harvesting knife. Then the hole is closed again and firmed.
Green asparagus is cut off with a small knife once it is tall enough for harvesting.
Length of the harvest season:
- Year 1: This is the year of planting, no harvest will take place.
- Year 2: Harvest will take place as long as there is the danger of frost destroying the growing stems. Mostly this is until 10 May.
- Year 3: The plants are now strong enough to produce good stems for a month. Mostly harvest will end during a warm period around 1 June.
- Year 4: From this year onward harvest will last for a whole season, until 24 June.
If polythene is used the harvest will have to be ended sooner to give the plants more time to recover.
It is best to end the harvest during a warm period. The stems will then fern out more quickly and produce heavier fern. Ending the harvest during a spell of cold weather mostly leads to poor fern growth.
Cooling and storage
Once harvested asparagus should be taken out of direct sunlight and cooled off with cold, fresh water as quickly as possible. Shock-coolers and transportable water tanks are out on the market. If it is kept too long in water that is too warm the asparagus will go sour. Therefore the water must be refreshed every 2-3 hours. The stems can be kept in water for a maximum period of 6 hours. Once the stems have been taken out of the water they should be stored in the dark.
Washing and grading
Recently harvested asparagus that dries up dirty is almost impossible to clean. Good machines for washing, cutting and grading asparagus are available nowadays. Grading will have to be done according to the demands of the buyer.
Before planting careful field preparation should take place. It is important to check carefully what should be done, when and how. Now corrections are still possible, once planting has taken place they will not be.
Covering with black/ white polythene
In order to achieve more hours of harvesting per day and to influence the speed of growth the asparagus beds can be covered in black / white polythene.
Because the polythene takes the light away from the beds, the stems will not color, this is the case whether the black side of the polythene is up or the white side. In the early days of the season and during cool periods you need to harvest only once every two days without a loss of quality. During cool periods having the black side of the polythene up will result in a slight increase of temperature on the bed which will increase production. During a very warm period having the white side of the polythene up will result in a decrease of temperature on the bed and a decrease in production. This prevents having to harvest a lot of asparagus at a low price.
Before harvesting the polythene will have to be removed from the bed either by hand or by machine. Immediately afterwards the polythene has to be put back on the bed.
In order to have your harvest earlier, you can consider to cover the beds -which already have been covered with black/white polytheen- with Thermo plastic and small hoops.
Asparagus is a crop that likes to root deeply. Root depth is largely determined by the resistance of the soil, especially by that of the subsoil. Research and practical experience have shown that the lifespan of an asparagus crop depends on the depth of the roots. Every 10 centimetres of rootable layer guarantees one year of harvest. Therefore it is very important to ensure that root depth is optimal. In practice this means that there should be a layer of at least 1 metre into which the plants can root. Because many types of soil have a top layer varying from 40 to 70 centimetres, it is necessary to make the remaining 30 to 60 centimetres accessible to the roots too. However it is important to realise that every field is different and requires its own approach. In order to find the right approach for your field contact your local Agricultural Advice Service. On soils where the rootable layer is less than one metre in most cases deep tillage will be necessary. Deep cultivating is only useful if there is a disturbing layer of a few centimetres. Profiles with a strongly loamy and compressed subsoil should only be ploughed under dry circumstances.
On soils where ground water can get into the rootable layer or where this situation may arise as a result of deep tillage you must never use deep tillage. Soils with a high water table are unsuitable for growing asparagus. Soils which are naturally rootable up to 1 metre, must not be plowed deeply. In this case preparing the soil to a depth of 50 centimetres will be enough. Spading is to be preferred because in that way fertilizer is carefully mixed through the top soil.
Green manure crops
If deep field preparation is needed for your field then this should be done at least a year before planting. In that way the soil can establish a good structure and natural moisture balance. In order to stimulate this it is a good idea to grow a green manure crop after digging the soil. In that way organic matter enters the soil and the roots of the plants will also improve the structure of the soil. If the soil has to be ploughed up to 50 centimetres, this should also be done as soon as possible, but at least half a year before asparagus is planted.
Rates of fertilizer for asparagus are dependent on soil test values. It is important to have a soil test done in time to establish especially the degree of acidity. Acidity is expressed in pH-KCI. For growing asparagus the pH-KCI should be over 5.8. If it is lower then additional calcium will be needed. The exact amount of calcium needed will depend on the outcome of the soil test, the organic matter levels and the kind of organic fertilizer you want to use. If the organic matter level is low you should be careful with providing calcium, as this fertilizer will lead to an increase in the breaking down of the so much needed organic matter. On fields where deep tillage is needed 2000 kg of calcium should be given on top of the amount indicated in the results of the soil test. This in order to correct the extra low pH of the subsoil. As organic matter is widely used nowadays, it will often not be necessary to use artificial fertilizer too. Magnesium however is an exception to the rule. Rather much of this is needed so that, depending on the type and amount of organic matter present, additional application may be necessary. Often magnesium is topdressed in the first year of growth.
Adding manure to the soil will increase its ability to retain moisture and will produce a nice loose structure of the beds. It is especially important to increase the moisture retention of light sandy soils. Organic manure will also improve the structure of heavy clay soil. But again, every field is different and requires its own approach. Still there is a general rule that applies at all times namely that all soils that require deep plowing need to be given 100m3 of manure per hectare beforehand. Please take into account national regulation with regard to the maximum amount of manure that is allowed. And soils which will be worked down to 50 centimetres should get 75 m3 of manure beforehand.
Mushroom compost is an organic fertilizer that is rich in calcium. Per 1000 kg this fertilizer contains about 50 kg of pure calcium. It is great for improving the quality of the soil. On light sandy soil the use of mushroom compost is best because here more cohesion of the soil is needed.