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…]
34 articles tagged "Soil Fertility and Fertilizers".
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…]
Soil pH plays an important role in plant nutrition. However, we might not be familiar with how nitrogen fertilizers influence soil pH over time. This article explains how nitrogen fertilizers influence soil pH over time and discusses some considerations in choosing N fertilizers. Plants can take up N in two forms: ammonium and nitrate. Ammonium (NH4+) is positively charged, while nitrate (NO3–) is negatively charged. When plant roots take up a charged ion, they typically release an ion with identical charges to maintain a balanced pH in plant cells. Following this rule, plants release a hydrogen ion (H+) when taking up an ammonium ion; and release a hydroxide ion (OH–) when taking up a nitrate ion. As a result, the net effect of taking up nitrate-N is to increase soil pH around root zones; taking up ammonium-N reduces rhizosphere soil pH. Nitrogen fertilizers contain N in the forms of ammonium,[Read More…]
There are certain questions within our culture for which there are simply no good answers. For example, how many times have we heard the classic question, “If a tree falls in a woods and there’s no one to hear it, does it still make a sound?” One question I’ve been asked recently, for which the answer is equally elusive, is “How long must I wait to grow vegetables after applying manure to the field?” With the 2015 season quickly winding down, it will soon be time to start making plans for next year’s crops. Part of those plans will undoubtedly include the question of manure use. While manure is a good source of plant nutrients and organic matter, it may also contain human pathogens that can be transferred onto fresh fruits and vegetables. After manure is applied to a field, the bacterial community in the manure changes as it adapts[Read More…]
Crop production, decomposition of organic matter, using ammonium-producing nitrogen fertilizers, and rainfall all lower soil pH. To maintain soil pH in the optimal range (6.5 to 6.8) for vegetable production, periodic application of lime is needed. The primary form of agricultural lime is calcium carbonate (CaCO3). It is the carbonate (CO3^2-) part that brings up soil pH. Whenever lime is applied, a large amount of calcium is also added to the soil. The good news is that calcium is an essential plant nutrient. Several vegetable problems that we are familiar with are caused by calcium deficiency for example, blossom end rot of tomatoes and peppers, and tip burn of cabbages. However, it should be noted that excess calcium might interfere with plant available magnesium and potassium. Therefore, it is always better to keep a balance of those nutrients. Some lime products are specified as dolomitic lime. Dolomitic lime is common[Read More…]
You might remember seeing cation exchange capacity in soil test reports. Recently, I have been asked about what it means. This is one of the important soil characteristics that we need to understand. Firstly, we need to know what cations are. Cations are positively charged ions. There are several. The ones very important for plant growth are calcium (Ca2+), magnesium (Mg2+) and potassium (K+). Soil particles are negatively charged. They can hold positive charged cations. When plants absorb nutrients from the soil solution, these bound nutrient cations are exchangeable with other cations in the soil solution and become plant available. Therefore, CEC describes the soil’s capacity to supply nutrient cations to the soil solution for plant uptake. Sands do not have the quantity of negative charges that clays and organic matter do. Thus sandy soils generally have the lowest CEC. Soils with lower CEC have less ability to retain cation[Read More…]
Pumpkins are off to good start and vines are starting to run, which means it is time to think about making a sidedress application of nitrogen. Typically, I recommend to split nitrogen applications half preplant and half sidedress. This is especially beneficial given all of our rain this season. If you relied on preplant N alone, with all of the rain, you may very well have lost almost all of your nitrogen with plants just now starting to set fruit. In my personal scenario, on light colored forest soils (common in So. IL and IN, 1.5-2.5 % organic matter) and given no-till with cereal grain residue I generally shoot for around 100-110 lbs. actual N per year (this would be decreased with more fertile, high organic matter soils) with about 50 lbs. of that at sidedress. In a tilled field, you could decrease this recommendation to around 80 lbs. actual N/A per year. This difference can[Read More…]
I have observed many fields of cantaloupes with magnesium deficiency or manganese toxicity. Watermelon plants may exhibit similar symptoms, but not as frequently as cantaloupe. Both disorders are related to acid (low pH) soils and usually occur in clusters in a field. Magnesium deficiency usually appears on sandy ridges and can be recognized by interveinal yellowing and death of tissues on older leaves (Figure 1). Manganese toxicity also first occurs on older leaves but appears in heavier or darker sands, often in low areas of the field. The diagnostic feature of manganese toxicity are the tiny pin-hole type lesions with yellow halos clustered between the veins (Figure 2). Leaves are best viewed when held up to the sun. These disorders can easily be confused with an infectious disease. In particular, magnesium deficiency has been confused with Alternaria leaf blight. Symptoms may seem to “spread” from areas of the lowest pH[Read More…]
Pinney Purdue Vegetable Field Day and Sweet Corn Sampler. Thursday, August 13, 2015. 4:00 p.m. – 8:00 p.m. CDT. Pinney Purdue Ag Center, 11402 S. County Line Rd., Wanatah, IN. Plot tours include soil health management and disease suppressive soils, tomatoes and peppers in high tunnels, and sweet corn varieties. Private Applicator Recertification (PARP) Credit available. To register, visit http://tinyurl.com/no6tosr or contact Lori Jolly-Brown, ljollybr@purdue.edu, or 765-494-1296. Beginning Farmer Tours. Free farm tours and networking events sponsored by Purdue Extension and Local Growers Guild. For more information and to register contact the Purdue Extension Education Store at www.edustore.purdue.edu or 888-EXT-INFO. August 18: Redbud Farm, home of Caprini Creamery, Spiceland, IN. Breakfast, networking, lunch and tour. September 8: Growing Places Indy, Indianapolis, IN. Lunch, networking session, tour. Urban produce farm with raised beds, u-pick, and greenhouses. September 14: Morning Harvest, Palmyra and Hardinsburg, IN. Breakfast, networking session, lunch and tour. Developing[Read More…]
