Fertilizing Greenhouse Crops

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Greenhouses are aids in the cultivation of crops. They are very effective in extending the growing seasons of certain crops and in protecting the crops from various adverse conditions which are brought about by weather conditions and predators. They enhance the capabilities of nature and of man to cultivate crops.

Indeed, greenhouses have become effective tools for man to properly cultivate crops. However, the proper growth and development of the crops are still in the hands of the cultivator. There are many factors that should be considered in maintaining a greenhouse. The temperature, humidity, ventilation, and shading are some of the factors that need attention when handling a greenhouse.

One of the most important factors in maintaining crops inside a greenhouse is fertilization. Maintaining an adequate amount of nutrition is needed to successfully sustain the growth and development of the crops inside a greenhouse.

More often than not, greenhouse crops are classified as heavy feeders. Heavy feeders are usually defined as crops that require large amounts of fertilizers. However, knowing that the crops are heavy feeders is not enough. Knowing the ratio of the elements that go into the fertilizers is as important as knowing the amount to be applied to the crops.

Recent research has proven that the nitrate, nitrogen, and ammonium balance will affect the growth of plants. In the State of Texas, cultivators are advised to use less than 50% of nitrogen in the form of ammonium. High amounts of ammonium in turn can cause foliage burn due to toxicity.


Most of the greenhouse crop cultivators today use a liquid feeding program to be able to supply nutrients to the crops. This kind of nutrient supply program can be supplemented by the slow release of granular fertilizers to the crops.

The frequency of the application of fertilizers can influence the growth of the plants as well. Most often, it is deemed important to be able to supply different nutrients during the peaking periods of the vegetative growth or reproductive (flower) growth of the crops. It is generally accepted that the best application system for fertilizers is a constant one. Constant feeding may be modified to be able to suit the needs of the plants. High soluble salts may be feed to the plants every other application.

The balance between nutrients should be maintained by the cultivator so as to avoid the occurance of deficiencies and toxicities in the plants.


There are many fertilizers that offer complete nutrients that are needed by the plants. These fertilizers contain nitrogen, potassium, and phosphorus which are the most essential elements that are needed by growing crops. There are also fertilizers that are custom-made for different crops.


Here are some key facts about the different basic elements that are needed by greenhouse crops:

Nitrogen- There are many different sources of nitrogen which can be used to supply the nutrient to the plants. Ammonium nitrate, potassium nitrate and calcium nitrate are some of the sources of nitrogen. If one is to supply nitrogen to the crops, he should not supply more than 50% of it in ammonium form.

Potassium- This is an essential element in the water utilization of the plants. The most common source of potassium for plants is potassium nitrate.

Phosphorus- Phosphorus is needed by the plants for their growth. It is usually supplied in large amounts. However, one must always be cautious in supplying phosphorus in large amounts for it may make other nutrients insoluble. This will make these nutrients impossible for plant absorption. The most common way of supplying phosphorus is through phosphoric acid or superphosphate.

Other nutrients

There are other nutrients that are needed to be able to provide complete nutrition to the crops. Plants need calcium, magnesium, sulfur, iron, zinc, copper, manganese, boron, molybdenum and chloride. Some of these are supplied through the growing medium but the others are supplied through supplemental application.

Both the primary and secondary nutrients should be incorporated to the feeding program. There are commercial blends which can suit the needs of the crops that are being cultivated in the greenhouse.

One must be able to monitor the amount and the balance of the different nutrients that are supplied to the crops in the greenhouse. Only through proper nutrition will the plants achieve their optimum growth and development potential. Quality crops can be harvested if one knows how to get around the nutritional requirements of the crops.

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