Petrus Langenhoven

Horticulture and Hydroponic Crop Specialist
Department of Horticulture and Landscape Architecture
Petrus Langenhoven's website

12 articles by this author

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It is essential, especially in hydroponics to start with a laboratory analysis of your source water. It is also important to do follow-up analysis throughout the year. Water quality can change especially where the water source is a well or a pond. In the article Taking Care of Plant Nutrition in Your High Tunnel-Water Alkalinity (Issue 627), we have discussed the importance of water alkalinity and how to correct high alkalinity levels. Additional elements of importance are Ca, Mg, S, Na, Cl, Fe and Mn. Knowing concentrations of these ions can help you to determine the need to purify water, leach or bleed more frequently, as well as to avoid these contaminants by choosing the appropriate fertilizer. Hard water might be generally associated with high alkalinity, but it is not always the case. Water hardness is a measure of the amount of dissolved calcium (Ca) and magnesium (Mg), expressed as if[Read More…]


In the past I have had many conversations with growers about plant nutrition in their high tunnels. A good plant nutrient management plan is an integral part of making a success of the crop you are growing. Plant nutrition is important to grow a strong and healthy seedling, the first step of a successful crop. Fertility management of especially vining crops (e.g. tomato, cucumber, peppers) are critical to achieving a good yield. It does not matter if you grow your crop in soil or in a soilless production system. Steering your crop to have the optimum balance between vegetative and reproductive growth will result in good yields over a longer period. It is important for growers to know what is in their water and soil. Therefore, soil analysis of a representative sample of the area that will be planted, and water analysis of a water sample from the source that[Read More…]


In issue 619 and 620 of the Vegetable Crops Hotline newsletter I gave you a brief background of the materials used and methods followed during the variety evaluation. I also discussed some of the challenges we encountered while doing the trial work. The varieties evaluated included: Entry # Variety 1 Sephia (Galia type) 2 Tirreno (Italian netted cantaloupe) 3 Rawan (Ananas type) 4 Rowena (Ananas type) 5 Migdal (Galia type) 6 Magnificenza (Italian netted cantaloupe) 7 Kenza (Charentais) 8 Karameza (fully netted cantaloupe) Preliminary data will be discussed in this article. Statistical analysis of all the data has not been concluded and therefore only treatment averages are reported. Yield: One of the criteria that was set for the variety trial was that the fruit size needed to be between 2 – 4 lbs. At Meig’s Farm Magnificenza, Sephia and Kenza produced fruit that varied in weight between 3.28 and 3.96[Read More…]


Figure 3. Plant infected with bacterial wilt, transmitted by spotted and stripped cucumber beetles

In issue 619 of the Vegetable Crops Hotline newsletter I reported that during April 2016 research focusing on the development of a unique market segment for Indiana melon growers was initiated. The research aims to demonstrate that through the use of high tunnels or greenhouses growers will be able to market melons earlier and increase yield while keeping quality undeniably high. Initial research focused on variety evaluation in a soil and soilless production system in high tunnels and a greenhouse, where the plants were trellised vertically. In the long term, we aim to establish the best production practices for high tunnel and greenhouse growers in Indiana and we will do a complete life cycle analysis to determine the profitability of the proposed production systems. Well it sounds all easy to do, but in reality I have experienced several production related issues during the growing season. Let me present to you[Read More…]


Figure 5: Tirreno, an Italian netted variety, orange flesh color

Indiana is a very important player in the domestic melon market. The total acreage planted in Indiana peaked in 1997 at 3,600 acres. In that year the total production was 455,000 cwt with an average income of $16.00 per cwt. The total farm value of production was $7,280,000 ($2,022 per acre). Yield has increased since 1997 from 130 cwt per acre to more than 200 cwt per acre in 2014. The Indiana melon growers have lost a significant share of the melon market since the 2011 and 2012 food borne illness outbreaks. Compared to 2011, the acreage planted and production in 2015 decreased by 900 acres and 52% (300,000 cwt), respectively. Quick Facts about Indiana Cantaloupe Transplant Production: March/April Planting Season: April – June Harvest Season: June – Sept. Plant Population (2.5 ft. x 6 ft.): 2,904 plants per acre Total acres planted: 2,100 acres (2013), 1,900 acres (2014), 1,800[Read More…]


Planting density plays an important role in the optimization of labor efficiency and productivity of your high tunnel. For the purpose of this article I will focus on tomato which is commonly grown as a high value crop on small farming operations. Usually growers select varieties according to customer (market) preference and then try to combine that with other attributes such as ease of production, disease tolerance/resistance and productivity (yield). Consumer preference usually helps to determine the fruit color, size and shape, and the sweetness (soluble solids) of the tomato variety to be grown. The grower again is interested in earliness, growth habit (determinate and indeterminate), and ease of pruning, trellising and picking. Most growers in Indiana choose determinate varieties for high tunnel production, because it has limited growth and is easy to stake and allows for early production (short production cycle), with most fruit ripening before field grown tomatoes[Read More…]


The cost of high tunnel and greenhouse infrastructure is high. The purchase price of high tunnels can vary between $2.00 and $7.00 per square foot, while climate controlled greenhouse costs can vary between $7.00 and $30.00 per square foot. Several factors have an impact on the costs of setting up new high tunnel or greenhouse infrastructure. Location – It is essential that the terrain selected for the construction of high tunnel and greenhouse infrastructure be well drained and level. High tunnels and greenhouses displace rainfall and provision has to be made for drainage infrastructure to redirect the water. Additionally, provision has to be made for new irrigation lines and if necessary, electricity and gas. As a general rule the distance of high tunnels and greenhouses from obstacles like trees or a building should be twice the height of that obstacle. This also applies to the distance between high tunnels or[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…]


Census data showed that in 2014 Indiana (12 acres), Illinois (11 acres) and Kentucky (13 acres) dedicated a very small portion of their food crop acreage to production under protection. According to the USDA National Agriculture Statistical Service 2014 Horticulture Specialties Census, of all the states surrounding Indiana, Ohio and Michigan have grown and sold the most food crops under protection, 24 and 25 acres, respectively. The use of high tunnels for vegetable production seems to be a novelty in the Midwest. But it can be a very important tool for every vegetable grower as it can be used to modify the growing environment for crop earliness, to protect the growing crop against environmental stress, to reduce disease and insect pressure and to extend the growing season. Covering the soil with a high tunnel prevents natural rainfall from washing or leaching nutrients and soluble salts from the soil, can lead[Read More…]


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…]