36 articles tagged "Crop Culture".

Figure 2. Demonstration soil solarization in a high tunnel.

Soil solarization can be used as a tool for soil disinfestation. It is accomplished by covering moist soil with transparent polyethylene film for 4 to 6 weeks in the summer. During this period, soils are heated to temperatures that are lethal to many soil pathogens, nematodes and weed seeds. This summer we conducted a demonstration trial in one of the high tunnels at Southwest Purdue Ag Center. The high tunnel was divided into three parts that were covered with 6-mil plastic, 1.5-mil plastic, and no plastic. The 6-mil plastic is the old covering of the high tunnel, and the 1.5-mil plastic was purchased from a paint store. Air temperature and soil temperature at the depth of 12 inches were recorded. We saw little difference between temperatures of the soils covered with 6-mil plastic and 1.5-mil plastic, which indicated that the old coverings of high tunnels are as good as thin[Read More…]


Figure 3: The pumpkin plants in the foreground of this photos have yellow leaves.

This time of year, I receive many complaints of pumpkin plants with yellow leaves. There can be many reasons why pumpkin plants have yellow leaves. The most common reason for yellow pumpkin leaves doesn’t have anything to do with a disease that can spread from plant to plant. Usually, the reason for the yellow pumpkin leaves has to do with lack of water, weather that has been too hot, nutrient deficiency or other stresses. The photos and discussion below will, I hope, illustrate my point. Let’s say you have a pumpkin field where you have pumpkin leaves that are yellow and you are wondering about the cause. You may want to ask yourself, which leaves are yellow and where are they yellow. In Figure 1, yellow pumpkin leaves may be observed.  When one looks a bit closer to find out where the yellow leaves are, one can see that the[Read More…]


Figure 1. Tomatoes are grown under a retractable tunnel system.

Tomato foliar diseases such as early blight, Septoria leaf blight, bacterial spot and speck that are commonly seen in the field are often less common on tomatoes grown in greenhouses and high tunnels. It is also true that high tunnel tomatoes have smoother skins than tomatoes grown in the fields. An important factor that determines this difference is rainfall. Pathogens that cause foliar diseases require leaves to be wet in order for infection to occur and rely on rain for spread. In addition, heavy rains cause tomato physiological disorders such as rain check. It is great that greenhouse and high tunnel structures prevent tomato canopies from direct exposure to rainfall, however, a significant initial investment is required for building the structures, and it is hard to relocate them after they are built. This summer, we used a retractable tunnel to grow tomatoes and peppers in the field (Figure 1). The tunnels[Read More…]


Figure 3. Broccoli ready to harvest.

A fall broccoli trial was conducted in a high tunnel at Southwest Purdue Ag Center in 2016 to test the potential of growing broccoli in high tunnels after tomatoes. This article describes what we found from the trial. Broccoli is a cool-season, frost-tolerant crop. The harvest portion of broccoli is the compact, slightly dome-shaped head that is comprised by numerous immature flower buds. Broccoli that forms a single large head and thick stalks requires 50-70 days to harvest. Vegetative growth occurs over a wide range of temperatures, but high-quality head development requires temperatures in the range of 54-68 ºF. If temperatures are below 41ºF, plant growth is significantly reduced. In Indiana, fall production of broccoli in an open-field can be challenging because of the relatively long growing season. But with increased heat accumulation in high tunnels, it is possible to have a second crop of broccoli following tomatoes. Broccoli can[Read More…]


Figure 1. A 30% black shade cloth was added to one of the high tunnels

Tomatoes growing in high tunnels are in the middle of or close to harvest. Developing and maturing fruit are under leaf canopies. On the top of the plants, many flowers are still blooming. These flowers will contribute to the second big harvest. Although tomatoes in June are most valuable, we certainly appreciate big, red and delicious tomatoes in July and August.  To ensure a sustained yield, it is important for these flowers to set fruit. The process of fruit set is very sensitive to excessively high temperatures. When temperatures rise above 100°F, even just for a few hours for a handful of days, tomato flowers may be aborted and fruit set fail. Night temperatures above 75°F may also cause tomato fruit set failure. In addition to fruit set, high temperatures affect fruit ripening process. Ethylene associated ripening decreases markedly at a temperature above 93°F. As a result, there might be an increasing number of[Read More…]


Figure 1. Grafted Fascination plants were grown on the right bed, ungrafted plants were grown on the left bed. The field were naturally infested with Fusarium wilt.

Watermelon production is threatened by Fusarium wilt, a widely distributed soilborne disease that can cause yield losses up to 100%. Currently, there are no watermelon varieties that are completely resistant to all races of Fusarium wilt. One way to control the disease is through grafting. The grafted plant combines a watermelon cultivar with a squash rootstock that has resistance to Fusarium wilt. In a study conducted at Southwest Purdue Ag Center (SWPAC), we found grafted watermelons significantly reduced disease incidence, and more than doubled watermelon yield in a Fusarium wilt infected field (Figure 1). In addition to controlling Fusarium wilt, grafted watermelons often show substantial advantages in early watermelon production due to cold tolerance from rootstocks. In a study conducted in Arizona, grafted watermelons that were transplanted in the field two months before soil temperatures reached 70 °F had twice as much yield as ungrafted watermelons grown in the same[Read More…]


Figure 1. A tomato plant showing nutrient deficiency symptoms.

Recent rain and cold conditions have brought detrimental effects to some of the early planted vegetables. In southwest Indiana, air temperatures have dropped into the 40s °F and soil temperatures have dropped into the 50s °F in early May. The low temperatures would have greatly inhibited absorption of water and mineral nutrients for many warm season vegetables. In one of our fields where watermelon and cantaloupe were transplanted on April 26, almost all the plants showed wilt symptoms on May 3. The wilt was caused by decreased water absorption from roots. The plants were dead due to the extended cold weather. Peppers and tomatoes that were planted about the same time maintained turgid and survived the cold period (Figure 1). But they showed symptoms similar to nutrient deficiency due to the reduced function of roots in the cold soil. The plants should start new growth when the temperature rises. Growers using low tunnels are more likely[Read More…]


Figure 2. A seedless cucumber

A plant is considered to be seedless if it is able to produce a fruit without or contain a much-reduced number of seeds, or in some cases, only present traces of aborted seeds. Seedlessness is a desirable fruit character because seeds are often hard, have a bad taste and produce hormones that lead to fruit deterioration. As a result, seedless fruit often has better quality and longer shelf lives. Seedless watermelons that were introduced in the 1990s have become the main type of watermelons grown in the U.S.  Besides seedless watermelons, breeders have developed seedless varieties for other fruiting vegetables. This article briefly introduces the different types of seedless fruit and discusses potential opportunities for growing theses varieties. Seedlessness exists in two forms. In the case of seedless watermelons, the fruit contains partially formed seeds that are aborted after fertilization (Figure 1.). Seedless watermelon plants are self-infertile. They must be[Read More…]


Effectively managing foliar diseases including late blight (LB), early blight (EB), and Septoria leaf spot (SLS), is one of the biggest challenges facing organic tomato growers. New, resistant hybrid varieties are available, but organic growers often plant heirloom varieties instead because they are perceived to have superior flavor and growers can save seed. Copper fungicides can provide fair control of these diseases, but these products are contact, not systemic, and must be applied often, which can negatively impact soil and water quality. The tomato organic management and improvement project (TOMI), led by Lori Hoagland in the Horticulture Department at Purdue, brings together a multidisciplinary team of researchers from across the U.S. to develop short, medium and long-term solutions to this challenge. In the short-term, the team aims to identify biofungicide and biostimulant combinations that can effectively control LB, EB and SLS. Greenhouse and field trials are underway testing various combinations[Read More…]


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There are several potential benefits of growing grafted tomatoes, particularly for early season tomato production in greenhouses or high tunnels. If you are interested in trying this technique but wondering whether it is possible to graft tomato plants by yourself, a Purdue extension publication, Techniques for Tomato Grafting, (https://extension.purdue.edu/extmedia/HO/HO-260-W.pdf ) provides a step-by-step guideline for small growers to explore this technique. A question I am often asked is: when should I start to plant the seeds to produce grafted plants? The chart below shows a general timeline and materials needed for producing grafted tomatoes on a small scale on your farm. As a general rule, the grafting process delays seedling growth for 6-7 days. The delay normally does not make a noticeable difference on the size of seedlings after the grafted plants are grown in a greenhouse for more than 2 weeks prior to transplant. As a matter of fact, grafted[Read More…]


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