Organic matter and beneficial microorganisms for greenhouse-grown vegetables

In Italy, there are over 40,000 hectares occupied by structures designed to protect various crops — namely tunnels and greenhouses of different sizes, either unheated or heated, covered with plastic, glass, or other more technological materials. Protected cultivation is most widespread in Central and Southern Italy and on the islands, with Lazio, Campania, Puglia, and Sicily leading the way. However, albeit on smaller areas, it is also found in the North, mainly in Veneto and Emilia-Romagna.

Vegetable crops dominate among those grown under cover, occupying about 70% of the greenhouses in our country. Floriculture and nursery production follow, at a considerable distance.

As we have already discussed in a previous article, many vegetable species are grown in Italy, both in open fields and under cover.

Under cover, we find fruit vegetables, leafy vegetables, and flower vegetables: tomato, watermelon, zucchini, melon, strawberry, lettuce, ready-to-eat leafy vegetables (“fourth range”), and bell pepper are the most extensively cultivated, but noteworthy are also spinach, eggplant, green bean, and asparagus.

Greenhouse cultivation thus involves both short-cycle vegetables, such as spinach, lettuce, strawberry, and certain green bean varieties, and long-cycle vegetables, such as tomato, pepper, eggplant, and melon.

Production is spread throughout the year.

…there is a reason.

In essence, protected cultivation, in addition to reducing the risk of crop damage from adverse weather conditions, accelerates germination in case of direct seeding, supports overcoming transplant stress, and in all cases positively influences vegetative growth due to the favorable temperatures created inside the greenhouse or tunnel.

The materials used for coverings are clearly permeable to solar radiation, which plants use for photosynthesis. At night, the soil and plants release the heat accumulated during the day, which is not dispersed into the surrounding atmosphere thanks to the covering. However, for optimal photosynthesis inside greenhouses, it is necessary to also create ideal conditions in terms of air humidity and carbon dioxide concentration.

Even if partly intuitive, it is worth emphasizing the reasons why protected crops are expanding in our country and beyond.

The covering ensures superior and consistent quality standards, allowing for optimal production management through careful planning. Yields are potentially higher, while the controlled environment may enable a reduction in the use of plant protection products.

Farmers can implement advanced agricultural techniques, including soilless cultivation, increasing their capacity to effectively meet the demands of large-scale distribution. Water resource management also becomes more efficient thanks to advanced systems such as drip irrigation.

Nevertheless, protection from adverse weather remains the main advantage of this approach.

Cultivating in greenhouses or tunnels does not come without drawbacks.

The first critical aspect to highlight is structural, even before being agronomic: greenhouses and tunnels operating in Italy still largely show a limited use of technology and automation, making it more difficult to control and maintain optimal environmental conditions for crop development and at the same time generating a high labor demand for their management. The European benchmark country for highly technological greenhouses is the Netherlands.

Then, purely phytosanitary considerations arise: air humidity levels in greenhouses or tunnels are often high (especially in the absence of forced ventilation systems), favoring the development of fungal diseases, such as downy mildew and gray mold (Botrytis), but also bacterial diseases like those caused by Pseudomonas syringae, Xanthomonas campestris, and Erwinia carotovora. The risk of infection and the extent of damage will also depend on whether leafy, fruit, or seed vegetables are being cultivated.

Certain pests are also particularly threatening in greenhouses. These include insects such as aphids, thrips, and whiteflies, and mites such as the red spider mite, which can damage the aerial parts of the crop and, in some cases, transmit viruses.

Soil can also be a source of problems: wireworm larvae (Coleoptera), fungi responsible for rots, and, above all, various species of nematodes can cause direct damage to roots and collars and/or, again, transmit viruses.

Another critical aspect to manage in protected cultivation is the fact that soils, due to the intensive exploitation they are subjected to, often exhibit suboptimal chemical, physical, and biological characteristics. The high temperatures in greenhouses or tunnels favor the mineralization of organic matter, which must be properly replenished to maintain soil friability suitable for the development of underground organs, which in some cases also represent the harvested product (carrots, potatoes, etc.).

The organic or organo-mineral fertilization of greenhouse-grown vegetables meets several needs. A good supply of humified organic matter promotes the maintenance of the correct soil moisture level and the bioavailability of nutrients, both those naturally present in the soil and those supplied with fertilization. This is thanks to the “transport” action performed by humic and fulvic acids. This is particularly important for long-cycle vegetable crops. The mineral fraction of organo-mineral fertilizers can instead more promptly meet the needs of short-cycle vegetable crops, but also of all crops, both short- and long-cycle, during initial stages of germination or post-transplant.

Finally, the supply of organic matter can promote the rebalancing of the soil microbiota, stimulating biodiversity and making the environment unfavorable to the dominance of a few, potentially pathogenic, species. The application of organic fertilizers inoculated with beneficial microorganisms can accelerate the “microbial rehabilitation” of tired and unbalanced soils.

Agr Bio Aktiv is an organic fertilizer inoculated with beneficial microorganisms, particularly suitable for use on short-cycle vegetables and for soil regeneration. In addition to providing organic matter and nutrients, it promotes and guides the proliferation of microorganisms beneficial to plant development in the soil. Its specific microbial composition, rich in Trichoderma, acts on soil and roots by limiting, through antagonism, the development of pathogenic agents responsible for certain root diseases.

Biosinergy is an organic fertilizer inoculated with beneficial microorganisms, suitable for use on medium- to long-cycle vegetables, and acts as a root system activator. It contains humified organic matter, rhizosphere bacteria, and mycorrhizal fungi inoculants. In addition to providing humified organic matter and nutrients, it promotes the formation of mycorrhizal symbioses and the development of the root system, thereby improving yield, plant health, and resistance to abiotic stresses, particularly water stress.

Nemaplus is an organic fertilizer containing, in addition to a highly humified organic fraction mainly composed of vegetable cakes, substances capable of creating a soil environment unfavorable to the development of soil-dwelling nematodes and parasitic insects, while at the same time promoting the development of beneficial microorganisms. The addition of Calcium makes Nemaplus an organic fertilizer with a specific targeted action.