39 articles tagged "Greenhouses & High Tunnels".

In a recent visit to a high tunnel, we observed a severe salinity problem on tomatoes. Approximately one month after planting , most tomato plants in the affected area had not sent out any new leaves. Roots did not grow at all (Figure 1).  After conducting a soil test, very high soluble salt level explains these symptoms. This article reviews the basics of soil salinity. Salinity describes salt content in the soil. Virtually all fertilizer materials are salts, but they vary in their effects to increase salt concentration in soil solutions. In a field situation, precipitation in the form of rain and snow tend to leach salts.  Since high tunnels exclude rain and snow, elevated salt levels are a common concern for high tunnel vegetable growers. Table 1 are the salt indexes of common fertilizers. If you are using a premixed fertilizer such as 12-12-12, check the fertilizer components on[Read More…]


Figure 1. Note stigma of tomato flower on the left was more exerted compared to flower on the right. In addition to temperatures, genetic factor, nutritional status and light might cause stigma exertion.

Maintaining temperature in the ideal range is very important for tomato fruit set. The optimum temperatures are 60-75°F (night) and 60-90°F (day). Studies showed that exposing plants to 3-h periods of temperatures above 104°F on two successive days may caused fruit set failure. Not only is the maximal temperature critical for fruit set, maintaining night temperature in the ideal range is also essential. Effects of high temperature on fruit set are primarily on the stage of pollen development, which occurs about nine days before flowers open. High temperatures also affects flower structure by causing stigma exertion that prevents pollen from successfully landing on the stigma (Figure 1). After pollination, pollen germination can be severely reduced at temperatures above 100°F. Preventing temperatures from reaching the extremely high level is important in high tunnel tomato production. Since biomass production and flower numbers are less likely to be affected by high temperatures compared to[Read More…]


In a previous article ‘Opportunities in Hydroponics’ (VCH 609) we discussed two types of Hydroponics, solution culture and medium culture. In this article we will focus on Growth Substrates (media), which form an integral part of medium culture. Growth substrates can be divided into two groups, organic and inorganic media. Inorganic media can be further divided into natural and synthetic. Media included under inorganic and natural are sand, gravel, rockwool, perlite, vermiculite, pumice, expanded clay aggregate, zeolite and volcanic tuff. Inorganic and synthetic media includes foam mats (polyurethane) polystyrene foam, oasis (plastic foam), hydrogel, and Biostrate felt®. Included under organic media is pine sawdust, pine bark, wood chips, peat moss, coconut coir, and rice hulls. The number of substrates available are not limited to this list. Using growth substrates instead of soil gives the grower several advantages: No need for arable land. Soilless growing media (substrates) is lightweight and can[Read More…]


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We went through an unseasonably cold period in early April (Figure 1). In southern Indiana, a few high tunnel tomato growers have already planted their crops. These plants may need some extra help. In Vincennes, IN, we used row covers to cover the newly planted tomatoes in high tunnels the past few nights, our recorded lowest temperature was 37 °F under row covers. Plants all look good. However, the temperature is apparently too cold for cucumbers. The majority of the early planted cucumbers in our high tunnels were dead. We are waiting for the weather to warm up (soil temperature at least above 60 °F) to reset the cucumbers. Please let us know if you also ran into problems in the past a few days because of the low temperature. It might be issues in the greenhouse, the high tunnels, or even the field. We would appreciate you sharing your experiences with us.      


Lettuce is grown in channels using the Nutrient Film Technique

Travelling through Indiana last summer, I realized that many growers plant their crops in soil inside their high tunnels or greenhouses. Soilless production offers different benefits and challenges. This is the first article in a series focusing on soilless crop production in high tunnels and greenhouses. Today we are discussing Hydroponics. What is Hydroponics?  The word hydroponics technically means ‘working water’, derived from the Latin words “hydro” meaning water and “ponos” meaning labor. Hydroponics is a method to grow plants using a mineral nutrient solution, in water and without soil. Two types of hydroponics are commonly found: a) solution culture, and b) medium culture. Solution culture types include continuous flow solution culture (Nutrient Film Technique) and Aeroponics. Medium culture types include ebb and flow sub-irrigation, run to waste, deep water culture and passive sub-irrigation systems. History.  The first research published on the production of spearmint in water was conducted by[Read More…]


​ Last year at the Southwest Purdue Agricultural Center (SWPAC) we conducted a tomato high tunnel trial described here. In this article, I would like to talk about the trial we will conduct in 2015, a repeat of the 2014 trial. In particular, I would like to talk about what we have done for fertility. Before deciding on a fertility scheme, it is critical to conduct a soil test each year. Our soil test from November 2014 showed that our high tunnels were low in sulfur, boron and moderately low in zinc. In fact, plant tissue tests conducted during the 2014 season were low for both sulfur and boron. As a result of these tissue tests, we added a 10% liquid boron product and ammonium thiosulfate (7%) to the fertigation during the 2014 season. However, the next set of tissue tests carried out during the 2014 season also came back[Read More…]


Over the last several years, the number of questions I have had about tomato production in high tunnels has increased dramatically. Since I am a plant pathologist, most of the questions I have been asked are about diseases of tomatoes in high tunnels. However, I also have been asked production questions. One particular question about tomato product that may impact disease severity is this: how many staked tomatoes can be grown in a high tunnel effectively? To be honest, the above question is one that I often ask myself when I observe high tunnels in Indiana. It isn’t necessarily one that is asked by growers. But maybe it should be. It has been my observation that growers often try to place too many staked tomatoes in a high tunnel. The result may include diseased tomato plants due to insufficient air circulation, poor quality fruit and even reduced yields. I was[Read More…]


Unit heaters that aren’t properly maintained can be a source of air pollution that harms seedlings. (Photo by E. Maynard)

Transplant production will soon begin in earnest if not already underway. It is sensible to check the greenhouse heating system before starting production to make sure it works and won’t pollute the air in the greenhouse. This checklist for gas or propane-fire unit heaters highlights some of the major points. If you are not familiar with the system a service technician can help. General Maintenance. Check for physical damage; Remove any obstruction in vent and exhaust systems; Make sure components are supported properly and securely. Fans and Blowers. Lubricate as needed; Check for smooth operation; Inspect for physical damage; Adjust belts as needed; Check connections to electrical power. Heat Exchangers and Burners. Inspect exchanger closely for cracks or corrosion where air-polluting gases can escape; Clean inside tube surfaces if required; Inspect for dark discoloration on metal which may be a sign of overheating and if found, investigate cause; Clean gas[Read More…]


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​The low tonight is forecasted to be 28 F. In preparation, we placed clear plastic over each row. This type of plastic is not vented. Therefore, one must be very careful to watch the temperature inside the tunnel when there is direct sunlight. Although we made it through last night, tomorrow morning will be the real test! UPDATE: After the cold night of Tueday morning–the tomatoes made it through fine. However, it didn’t get as cold as predicted. We found it difficult to manage the low tunnels when the sun was out during the day. Growers should be very careful about clear plastic tunnels without vents. The tunnels can get very hot. Clear plastic low tunnels over the tomatoes in the high tunnel. Note that there are no vents. Care must be taken to vent low tunnels if necessary. This can be done by opening the ends. The ends would[Read More…]


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