Crop biofortification

Written by Fahim Nawaz

A GROWTH rate of 1.2 per cent was estimated in the agriculture sector of the country during 2010-11 with a significant increase in staple food crops like wheat, maize and sugarcane.

Crop biofortificationThese crops are grown to feed the country’s ever increasing population with little awareness about the hidden malnutrition. No
real effort has been made to enrich crops with nutritional value required for improving human health.

Most farmers are illiterate and do not have knowledge about modern farming. This is a real challenge for the extension workers, breeders and researchers to create awareness among them. Farmers need to be encouraged to replace modern varieties periodically, as these lose their resistance to new evolving strains of disease.

In this respect, the role of plant breeders is very important and challenging. Plant breeding technology has great impact as breeding of micronutrient dense staple food crops can deliver most of the micronutrients. Micronutrient dense staple food crops can be introduced by using best traditional practices and biotechnology to achieve pro-vitamin A, zinc and iron concentrations.

Plant breeders can work with nutritionists to introduce high nutrient traits into agronomically superior varieties and to determine the quantity of a nutrient required in a crop to improve human nutrition. The loss of nutrients also occurs during harvesting, storage, processing, or cooking and these losses must be considered before determining breeding target levels.

International research organisations like Future Harvest Centers of the Consultative Group on International Agricultural Research have been working in the country to evaluate the feasibility of using modern breeding techniques to develop micronutrient-enriched new varieties of staple crops.

Another international organisation Harvest Plus is working in collaboration with the scientists of Aga Khan University, Pakistan Agriculture Research Council (PARC) and University of Agriculture, Faisalabad, to develop zinc-fed wheat crop. The scientists in these research organisations are working on the breeding strategy to incorporate high zinc and iron traits into wheat varieties resistant to new strains of yellow and stem rust but their efforts would not bear fruit until farmers realise the importance of bio-fortification of crops.

The enrichment of food crops with nutrients can also be achieved by adaptation of suitable agronomic practices. A recent research has shown that trace minerals also help plants to resist disease and biotic stresses. The survival of more seedlings will ensure rapid initial growth which ultimately results in higher yields particularly in trace mineral ‘deficient’ soils in arid regions.

This suggests the dual benefit of enrichment of crops with nutrients.

The extension workers can play a pivotal role in introducing new technology among farming communities. The best agronomic practices would help preserve and enhance nutrient balance of micronutrient dense seeds. In fact, biofortification would help increase farm productivity in an environmentally-beneficial way.

It is time that agriculture and nutrition disciplines collaborate to improve human nutrition. A multidisciplinary research team of scientists from different disciplines should be made to work in this direction.

Plant breeders should be encouraged to include micronutrients in their breeding portfolios along with higher yield, disease resistance and other agronomic traits. Public health officials must understand the importance of micronutrients consumption in food and help end micronutrient malnutrition.

The biofortification of crops would get support among farmers, research scientists, health professionals, and policymakers, once it is proven a viable, cost-efficient and effective solution for combating micronutrient malnutrition.

Courtesy: Dawn

Soil Testing: Give Your Ground a Surprise Pop Quiz

Written by  Annie Spiegelman

Having your yard landscaped can be expensive; so, before you or someone else starts digging, be sure to take the soil test so your money doesn’t go to waste

If you’re thinking about here are some questions to first ask yourself (and anyone else who looks remotely interested) about your backyard soil:

  • Is the soil worked easily?
  • Is the soil full of living organisms?
  • Are earthworms abundant in the soil?
  • Is water and air available for plant growth?
  • Does my garden make me look good?

“I’m really, really mystified by homeowners who will plop down $30,000 to a landscape designer who will come up with a plant palette without ever thinking to take a spoonful of soil to test it first,” says Professor Stephen Andrews, soil scientist at UC Berkeley. “One of the criteria for selecting a landscape architect is to give them a soil quiz! Ask them what kind of soil test they will be providing. Be an informed consumer.”

So, after you’re done hating your compacted soil and admiring yourself in front of the mirror in your new garden hat, it’s time to get scientific. Why? Because we compost- spinning tree huggers believe all home gardeners caring for a plot of land, large or small, can be become superb stewards of their gift from Mother Nature by learning a little soil science.

“If you’re going to do any type of landscaping project, make sure to test your soil first to understand what kind of a baseline you have,” says Andrews. “If you’re changing a large backyard area, doing drainage work or you’ve just purchased a new home, go get a ‘commercial’ soil test done. It may cost you a few hundred dollars, but you’ll have a thorough analysis and interpretation of your land. The soil scientists at the testing company will give you specific advice on how to proceed.”  

For the rest of us, who don’t have the green to spend on the brown, it’s perfectly fine to take the mom-and-pop route. Head down to your local plant nursery and purchase a home garden test kit. A good soil test will run about $20. Andrews recommends Mosser Lee’s Soil Master kit “because of the educational information included. It’s also a simple test. It’s color-coated and it’s idiot-proof, I promise. Do it with the kids or grandkids. Or, get the entire neighborhood and have a soil testing barbecue! One test kit will have enough tubes to do 10 soil tests. You may be the diva who does everything organic, but…you’re living next to Charlie Chevron who uses every petrochemical on the planet. Get together and literally talk dirt.”

soil testingWith the home soil test, you’ll be testing your soil’s pH. The pH level will tell you if nutrients are actually available to your plants or if you’re just out fertilizing, polluting and wasting your hard-earned cash on garden products.

“The ideal pH of soil for many common plants is 6.5. The reason we want the soil to be slighty acidic is because the plant nutrients are carried in a solution. If it’s slightly acidic, the nutrients can dissolve and can be transported,” says Andrews. “If the pH is too alkaline, the nutrients will sit there like lead balls of pasta, not going anywhere. By having it slightly acidic you have the best pH for nutrient uptake. To lower the pH, use coffee grounds, tea bags, sulfur, aged animal manure or compost. To raise the pH, add limestone or oyster or egg shells.”

Home tests also check the availability of your soil’s macronutrients: nitrogen (N), phosphorus (P) and potassium (K). These are the main nutrients and minerals needed by your plants (which is why you’ll see the letters NPK on fertilizer containers). Once you know which nutrients are already hanging out in your soil, you won’t be wasting money on unnecessary products.

When collecting your home soil sample, choose a few different sections of your yard. For instance, your edible garden in raised beds would be one test area while your front lawn, a slope or a woody spot would each be a separate area to test. “For each chosen area, do a representative sampling. Pick ten to fifteen different spots in that area and dig down 6-8 in.,” recommends Andrews. “Remove critters, rocks, roots and plant material. You just want soil parts. Take all samples from that area and mix them into a plastic baggie. Label the bag and the area accordingly. For a lawn, dig down only 2-3 in..”

If you’ve decided to do the commercial test, you’ll want to decide just how comprehensive a test you need. Andrews suggests testing for pH nutrient availability, particle size analysis, bulk density, moisture content, organic matter content, macro- and micronutrients and soluble salts. If you live in an urban area and are growing edibles, or in an older home where lead contamination from paint is prevalent, heavy metals testing should be done as well.

As mentioned above, commercial soil testing should be done when you first move into a home. It should also be done every ten years or so, depending on your budget and your gardening success or utter failure. The home soil test, on the other hand, would be useful to do any time a considerable amount of plants in your yard look beaten down, chewed up or super sluggish. (Gardeners don’t have patience for lollygagging plants. Testing your soil twice a year—once in the spring and again in the fall—is especially helpful if you’re growing fruits and vegetables year round.

“Cold season crops have different needs than warm season crops. Like us, our underground soil friends slow down when it’s colder outside,” says Andrews. “The bacteria slow down; but, once the soil warms up, the disco lights come on and they’re ready to party!”

Source: maximum yield

ROLE OF PRUNING IN CITRUS, TIMING AND ITS IMPACT ON TREE AND FRUIT

*Muhammad Shafique Khalid, *Muhammad. Amin, *Omer Hafeez, **Muhammad Umar and **Faheem Haider

* PhD Scholar, Institute of Horticultural Sciences, University of Agriculture Faisalabad

** M.Sc Scholar Institute of Horticultural Sciences, University of Agriculture Faisalabad

Pruning fruit trees is a technique that is employed by gardeners to control growth, remove dead or diseased wood or stimulate the formation of flowers and fruit buds. Pruning of tree fruits and vines is a horticultural practice handed down from ancient time. It has in common the objectives of manipulating various aspects of vegetative and fruiting behaviour. Some of the benefits traditionally attributed to pruning and girdling in the practical culture of citrus have been called into question by field research in the past few decades.

PRUNING IN CITRUSCitrus is a perennial crop. As long as the trees remain healthy, they can flower and fruit for years on end, some times for as long as twenty or thirty years (Mazhar and Nawaz, 2006). However, if the trees are not maintained at a proper size, the height and canopy shape of mature trees in a citrus orchard will not be uniform and the branches will be too crowded. In a crowded orchard, disease and pests can spread quickly. Fruit quality tends to be poor, and trees may not bear fruit every year. A proper training and pruning program is essential for the maintenance of a healthy and productive orchard.

Benefits of pruning in citrus

The major benifits of pruning in citrus include:

  1. The total effective leaf area is increased resulting in increased photosynthesis by exposing the leaves to light and air.
  2. The water use efficiency and the conversion of available plant nutrients is increased.
  3. By removing diseased or infested branches and exposing leaves to light and air, a good training and pruning program helps control pests and diseases in citrus orchard.
  4. Proper pruning of the tree keeps it in the right size.
  5. It also increases the vigor of the tree, enhances its tolerance of various stresses, and helps maintain the most efficient balance between vegetative growth and fruiting.

Pruning and skirting (removal of low-hanging limbs) affects on canopy temperature, relative humidity (RH), and fruit yield and quality of Orlando’ tangelo trees (Citrus paradisi Macf. x Citrus reticulata Blanco). Pruning increased the percentage of large fruit and reduced the percentage of small fruit. (Morales et al., 2000).

The alternate tendency exists across all varieties of the citrus. To attenuate alternate bearing, pruning and fertilization are processes the only options which growers can exploit. For pruning to be effective, it must be done after the end of an “off” or light crop year, i.e., prior to the season of anticipated high production. It should not matter whether the pruning is conducted before or after the bloom, as the results should be about the same, reduction in production during the season following pruning (Mazhar and Nawaz, 2006).

Eissenstat and Duncan (1992) reported that total reducing and ketone sugars (free fructose, sucrose and fructans) in the fine roots were less in pruned than unpruned trees 20 days after pruning, but not thereafter. By 30 days after pruning, at least 20% of the roots of the pruned trees at a soil depth of 9 to 35 cm apparently died. By 63 days after pruning, root length density had recovered to that of the unpruned trees, although starch reserves were 18% less in the fine roots of pruned than unpruned trees at this time.

Growers should select the correct time for the pruning. Since citrus trees are evergreen, they do not have a period of true dormancy. However, the metabolism of the tree is less active in the period after fruit harvesting. This period of reduced metabolism activity is the time to prune. Light pruning can also be conducted at other seasons to remove unwanted and overcrowded shoots.

Tree age is another important factor that should be taken into account, because the tree’s response to pruning varies according to age (Mazhar and Nawaz, 2006). Therefore citrus growers have to recognize the characteristics of the different cultivars they are growing in order to select the best training and pruning system for their orchards.

References:

Eissenstat D.M and L.W Duncan.1992. Root growth and carbohydrate responses in bearing citrus trees following partial canopy removal. Tree Physiol. 10(3): 245-57.

Mazhar, M.S. and M.A. Nawaz. 2006. Pruning as a tool to improve yields in citrus. Pakistan Horticulture. 4(1): 23-25.

Morales, P., F.S. Davies and R.C Littell. 2000. Pruning and skirting affect canopy microclimate, yields, and fruit quality of ‘Orlando’ tangelo. Hort Science. 35: 30-35.

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KINNOW MANDARIN: THE PREMIER CITRUS OF PAKISTAN

*Muhammad Shafique Khalid,** Aman Ullah Malik,* Samina Khalid,* Omer Hafeez and *M. Amin

 

* PhD Scholar, Institute of Horticultural Sciences, University of Agriculture Faisalabad

**Professor, Institute of Horticultural Sciences, University of Agriculture Faisalabad

 

 

Kinnow mandarin (Citrus reticulata Blanco) is one of the major citrus cultivars and is extensively grown in Pakistan. It was developed by H.B. Frost at California as hybrid (F1 generation) between King and Willow leaf during 1915; released in 1935 and was introduced in sub continent during 1943-44. The first plantation in Pakistan was made at Experimental Fruit Garden of Punjab Agricultural College and Research Institute Lyallpur (now University of Agriculture, Faisalabad). Since its introduction, it has flourished well under the agro-ecological conditions of Punjab, Pakistan. According to an estimate approximately 95% of the world Kinnow is being produced in Pakistan (Anonymous, 2011). The Kinnow fruit of Pakistan possesses superior taste, flavor and aroma and competes well with other citrus cultivars in qualitative and nutritive attributes as under:

KINNOW MANDARIN THE PREMIER CITRUS OF PAKISTANØ Kinnow grown in Pakistan is naturally coloured, no chemical degreening is needed.

Ø The fruit peel off very easily unlike other citrus members.

Ø Kinnow mandarin fruits have higher juice contents i.e. 53% as compared to other citrus varieties e.g. Grapefruit (48.50%), Blood Red (37.7%). Even Kinnow is juicier than Clementine mandarin.

Ø Kinnow has 18.59% more vitamin C as compared to Blood Red orange, 9.9% than Musambi and 6.65% than Grapefruit. Vitamin C protects against cancer by scavenging their causing compounds.

Ø As far as minerals contents (calcium, iron, magnesium, potassium and sodium) are concerned, Kinnow possess 11.11% more calcium than Grape fruit, 14.50% than Blood Red and 16.27% than Musambi. Similarly Kinnow has 10.73% higher Magnesium contents than Grapefruit, 14.19% than Blood Red and 15.87% than Musambi. Iron contents are also 7.93% greater in Kinnow than Grapefruit, 11.47% than Blood Red and 28.30% than Musambi.

Ø Kinnow mandarin is also loaded with photochemicals like antioxidants and phenolic compounds. Almost 16.18% high phenolic compounds are present in Kinnow as compared to Blood Red.

Ø Kinnow has about 16.14%, 6.05% and 47.02% higher antioxidant activity than that of Blood Red, Hamlin and Lemon respectively. These compounds are very important due to their antiallergic, anti inflammatory, anticancer and antiviral properties

Ø Kinnow mandarin is good source of Folic acid, β-carotene etc. Folic acid is recommended before and early pregnancy for healthy babies (avoiding neural tube defects). While β-carotene is important in immune response and also acts as antioxidant.

Ø Consumption of Kinnow fruits can provide sufficient quantities of pectin in diet as juice sac walls and capillary membranes are effective source of pectin. Pectin affects several metabolic and digestive processes most important of them are its affect on glucose absorption and maintaining cholesterol levels. Dietary fiber also reduces the chances of colon cancer by absorbing carcinogen in gastrointestinal tract.

 

Table 1: Biochemical profile of Kinnow mandarin of Pakistan

1. Juice (%age)* 51-54

2. TSS oBrix* 09-10.3

3. Acidity (%age)* 0.55-1.0

4. Ascorbic acid (mg/100ml)* 41-53

5. Total Sugars (%age)* 7.2-7.5

6. Total phenolics compound (ppm) * 852-1059

7. Antioxidant activity (I %)* 65-73

8. Calcium (mg/100ml)+ 0.750

9. Iron (mg/100ml)+ 0.338

10. Magnesium (mg/100ml)+ 7.48

SOURCE: *Khalid and Malik (unpublished data); +Rashid, (2007);

Variation exists for different maturity stages

Table 2: Biochemical profile of other citrus varieties grown in Pakistan.

Grape fruit Blood Red Musambi

1. Juice (%age)** * 48.50 37.70 54.0

2. TSS oBrix+ 7.50 10.0 10.5

3. Acidity (%age) + 1.39 0.55 0.32

4. Ascorbic acid (mg/100ml)+ 46.39 36.38 43.45

5. Total Sugars (%age) + 5.3 5.55 8.51

6. Total phenolics compound (ppm) —- 255.0** —-

7. Antioxidant activity (I %) —- 49.1++ —-

8. Calcium (mg/100ml) + 0.602 0.562 0.542

9. Iron (mg/100ml)+ 0.287 0.268 0.188

10. Magnesium (mg/100ml)+ 6.03 5.62 5.42

SOURCE: + Rashid, (2007); ** Tounsi et al. (2010); ++Scalzo et al. (2004); ** *Ikhtiar et al. (2010)

Variation exists for different maturity stages

Table 2: Biochemical profile of citrus varieties grown in USA.

  Tangerine Clementine Navel Valencia Grapefruit Lemon
Energy Kcal 53 47 49 49 32 29
Total lipids (g) 0.31 0.15 0.15 0.30 0.10 0.30
Carbohydrates(g) 13.34 12.02 12.54 11.89 8.08 9.32
Dietary fiber (g) 1.8 1.7 2.2 2.5 1.6 0.4
β Carotene (mcg) 155 —- 87 —- 552 3
α Carotene(mcg) 101 —- 7 —- 4 1
β Crytoxanthin, (mcg) 407 —- 116 —- 6 20
Vitamin A IU(IU) 681 —- 247 230 927 22
Vitamin E (mg) 0.20 0.20 0.15 —- 0.13 0.15
Folate (mcg) 16 —- 34 39 10 11

SOURCE: USDA National Nutrient database (2010)

It is clearly concluded from above facts and figures that Tangerine including Kinnow has higher energy, carbohydrates, carotenes, Vitamins, Minerals contents (Ca, Mg and Iron), Juice percentage, Phenolics compound and Antioxidant activity than other citrus varieties grown nationally and internationally. Its distinguished features like natural color, easy peel, aroma, size and good blend of TSS to acidity ratio is an asset and worth for consumer attraction and export of Kinnow from the country.

References:

Anonymous, 2010. U.S. Department of Agriculture, Agriculture research service data base for standard reference release 23. Available at: www.ars.usd.gov/ba/bhnrc/ndl. Date of retrieval: 25 Jan 2011.

Anonymous, 2011. All about Citrus. Available at: http://www.pakissan.com /english/allabout/ orchards/ citrus/index.shtml. Date of retrieval: 25 Jan 2011.

Khalid, S. and Malik, A.U. Fruit quality and storability of Kinnow mandarin (Citrus reticulata Blanco) in relation to tree age. (Unpublished data).

Khan, I., Shah, Z., Saeed, M. and Shah, H. 2010. Phytochemical analysis of Citrus sinensis, Citrus reticulata and Citrus paradise. J. Chem. Soc. Pak., Vol. 32(6). 774-780.

Rashid, A. 2007. Evaluation of organic acids and mineral contents in citrus juices. M.Sc (Hons) Thesis, National Institute of Food Science and Technology (NIFSAT), University of Agricutlure, Faisalabad, Pakistan.

Scalzoa, R.L., Iannoccari, T., Summa, C., Morelli, R. and Rapisarda, P. 2004. Effect of thermal treatments on antioxidant and antiradical activity of blood orange juice. Food Chem. 85, 41–47.

Tounsi, M. S., Wannes, W. A. Ouerghemmi, I. Jegham, S. Njima, Y. B., Hamdaoui, G. Zemnib, H. and Marzouka, B. 2011. Juice components and antioxidant capacity of four Tunisian Citrus varieties. J Sci Food Agric. 91: 142–151.

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Promoting Floriculture

By Dr S M Alam

FLORICULTURE is fast emerging as a profitable venture and the country is also earning a sizable foreign exchange by exporting roses to Middle East and European countries.
The local production of cut flowers is estimated at about 10,000-12,000 tons per annum. Roses are popular crop for both domestic and commercial cut flowers. They are harvested and cut when in bud and held in refrigerated conditions until ready for display at their point of sale.
Both local and grafted roses are grown in all the four provinces of the country, but Punjab has lion’s share in production of grafted roses and supply to all the cities of the country.
Promoting FloricultureRoses may be grown in any well-drained soil with optimum sunlight. Most rose varieties are grown by budding on lower portion of a plant and propagated from seeds or cuttings. Clay soils, warm temperatures are always preferred, and the rose plants grow best when not set among other plants. Cow manure is the preferred fertilizer for rose cultivation, but other organic fertilisers, especially composts, are also used.
Rose plants usually require severe pruning, which must be adapted to the intended use of the flowers. Pattoki, a small town about 80-km south of Lahore, has emerged as a leading home for cut flower floriculture technology. More than one million pieces of cut flowers are sent daily from this town to all the major cities of the country. The availability of flowers and ornamental plants has recently increased with change in crop production priorities and rise in living standards. The availability of pick flowers of red rose in use since ages for garlands has increased manifold. Additionally, cut flowers for flowers arrangements have sprung up in market due to demand pull by the local consumers.
The demand for long stem roses, tube roses, gladioli has tremendously increased. In order to explain the cultivation of these plants, import of quality hybrid flower seeds and planting material may be allowed free of duty to promote production of quality leading to export. The small items of machinery and shading nets to be used by the flowers and ornamental plant nurseries should be exempted from the levy of duty.

Roses are best known as ornamental plants grown for their flowers in the garden and sometimes indoors. They have been also used for commercial perfumery and commercial cut flower crops. Some are used as landscape plants, for hedging and for other utilitarian purposes such as game cover. They also have minor medicinal uses. The majority of ornamental roses are selected hybrids. A few, mostly species roses are grown for scented foliage, ornamental thorns or for their ornamental fruit.
Rose perfumes are made from attar of roses or rose oil, which is a mixture of volatile essential oils obtained by steam distilling the crushed petals of roses. An associated product is rose water which is used for cooking, cosmetics, medicine and in religious practices. Rose water made as a byproduct of rose oil production, is widely used in Asian and Middle Eastern cuisine. The French are known for their rose syrup, most commonly made from an extract of rose petals.
By observing the rapid growth in cut flower export, this business can become Pakistan’s second largest export sector after textile if the government encourages the cut flower growers by facilitating them to provide better technology in the year round production, refrigerated transportation and exploring more foreign markets.
The world trade of cut flowers runs in billion of dollars and Holland serves as the centre of cut flower business.
The cut flowers trade is tremendously increasing due to its demand worldwide. The cut flowers importing countries are: Australia, Denmark, Dubai, France, Italy, Saudi Arabia, South Africa, Syria, Turkey, U.S.A. and United Kingdom and the major suppliers are Colombia, Ecuador, India, Israel, Kenya and Zimbabwe.
Courtesy: The DAWN

Cultural Methods of Vegetable Disease Control

Most vegetables are susceptible to one or more diseases. You can, therefore, anticipate disease problems sooner or later in your vegetable garden. By following good cultural practices and taking preventive measures, your chances of garden failure due to disease problems can be reduced.

Cultural Methods of Vegetable Disease ControlGarden site selection is important to pro-duce high yields of healthy vegetables. Trying to grow vegetables on a poor site is one of the main causes of garden failure. Although few people will have ideal garden sites, they should select the best site available.

Garden sites should not be within the drip line of large trees. Avoid planting near black walnut trees, since they produce a root sub-stance that is toxic to certain vegetables, especially tomatoes. The garden site should be slightly sloped to provide good water and air drainage through the soil.

Excess soil moisture can damage vegetable roots, as well as promote root diseases caused by certain fungi. Air movement through the garden is also important to help dry the foliage, thus reducing the chances of fungal and bacterial infections. Garden sites with good air drainage are less likely to be damaged by late frosts.

Most garden vegetables require full sunlight for maximum production. Sunlight also hastens drying of foliage. Soil tillage should be done early enough, prior to planting, to allow decomposition of raw organic matter such as manure or green plant material. This usually requires about six weeks under warm temperatures and longer at low temperatures. Organic material that has not decomposed can be a source of disease organisms and can also promote development of certain diseases such as root and stem rots. Applying nitrogen fertilizer before plowing or tilling green plant material into the soil will hasten its de-composition.Cultural Methods of Vegetable Disease Control2

Crop rotation will help prevent the buildup of disease-causing organisms in the soil. Some disease causing organisms affect one vegetable or group of vegetables, but may not affect an-other. Several vegetables of the same family, such as squash, cucumbers and cantaloupes, may be affected by the same disease. Therefore, it is not a good practice to grow plants of the same family in rotation. Table 1 gives crop groupings for rotation to control soil-borne diseases. At least a three-year rotation is suggested for vegetable crops.

Sanitation is very important in controlling vegetable diseases. Many disease-causing organ-isms survive the winter in plant debris, cull fruit or plant stubble left in the garden. Any practice that will eliminate these overwintering sites for fungi, bacteria, viruses and nematodes will reduce the occurrence of disease problems the following year. Removal or plowing-under of crop stubble and trash helps destroy overwintering populations of disease organisms. Some disease-causing organisms are able to survive the off season on contaminated equipment or containers. Equipment that has been used in disease-infested vegetable gardens or containers used in handling diseased vegetables should be disinfested before being used again.

Disease-free seed and transplants are a must in vegetable production. Seed should not be saved from diseased plants. Always buy seed from a reputable dealer, since you normally cannot tell from their external appearance if seed are contaminated with disease-causing organisms.

Certain geographical areas, such as the arid western states, can produce disease-free seed because of climatic conditions. Seed from these areas should be stipulated in your seed orders. Gardeners starting their crop from transplants should, likewise, insist on disease-free plants.

Seed treatments vary, depending on the crop as well as the disease to be controlled. Some disease-causing organisms are carried on the surface of seed and can be controlled by a simple fungicide treatment. Fungicides are not effective against those organisms carried beneath the seed coat.

Fungicides applied to seed also give young seedlings some protection from soil-borne disease organisms as they germinate and emerge. Such treatments, however, do not control organisms that attack the plant after the seedling stage.

A seed treatment is usually applied by the company from which the seed is purchased. Home-grown seed can be treated at home with relative ease. Thiram or Captan fungicides can be used as seed treatments on most vegetable crops. Use these protectant fungicides according to instructions on the label. For small quantities of seed, such as packets, apply sufficient fungicide to coat the seed surface. Simply place a small quantity (comparable to the size of a match head) in the packet, reclose and shake to coat the seed with the fungicide.

Planting dates can be an effective tool in reducing diseases of vegetables. Okra, for in-stance, requires warm soil for good germination and growth. If planted when the soil is still cold, the seeds will rot, or if they do germinate, they will probably develop damping-off or stem rot. Some crops, such as corn and beans, should be planted as early as the weather permits to escape severe virus infections. Aphids that transmit viruses are usually at lower population levels early in the season.

Mulches can be used to conserve moisture, keep fruit clean and prevent diseases. Mulches reduce fruit rot on crops, such as strawberries, tomatoes, squash, cucumbers and melons by preventing direct contact with the soil. Mulching will reduce splashing of soil onto lower fruit and foliage by rain.

Staking or trellising tomatoes, pole or half runner beans and cucumbers will prevent soil contact with the foliage and fruit. Air circulation will be better if these plants are trellised, thus promoting better drying of foliage and reducing diseases. Pesticides can be more effectively applied to trellised plants.

Watering can influence the development and severity of many foliage diseases. Wet foliage is favorable for the development of most diseases. To reduce infections, apply irrigation water to the soil rather than the foliage. If water must be applied to the foliage, then it should be done in late morning or mid-afternoon to allow the foliage to dry before evening.

Maintaining uniform soil moisture can re-duce problems such as blossom end rot of pe-pers and tomatoes. Excessive soil moisture can result in increased root and stem rot diseases. It is best to work in the garden when the foliage is dry to reduce disease spread. Bacterial diseases of tomatoes, beans and other crops are readily spread on hands and clothing of workers when the foliage is wet.

Use of resistant varieties is one of the most economical ways of controlling vegetable diseases. Resistant varieties should be used in areas where diseases are present or where the soil is known to be infested with disease-causing organisms. Resistant varieties should be used even when rotation is practiced.

Hydroponics for Home Gardeners

By: J. Raymond Kessler Jr., Extension Specialist, Associate Professor; J. David Williams, Department Head and former Extension Specialist; and Robyn Howe, Undergraduate Student, all in Horticulture, Auburn University

Hydroponics1For centuries, civilizations throughout the world have experimented with soilless gardening, from the ancient Babylonians to the Aztec Indians. Marco Polo spoke of China’s magnificent floating gardens, and there is documentation that the Egyptians practiced primitive hydroponics. It was not until the 1930s, however, that this “new” form of gardening began to receive notice due to the notable experimentation of Dr. W.E. Gericke of the University of California. Gericke, often called the “father of modern hydroponics,” coined the term hydroponics, which literally means “working with water.” Since that time, many developments have been made, and hydroponic gardening continues to grow and thrive in popularity and usage.

Hydroponics is, simply put, growing plants without soil. The discovery was made years ago that it was not the actual soil that plants need to grow is the mineral nutrients held by soil particles or those unleashed through the action of bacteria and worms. The nutrients slowly dissolve in the surrounding soil-water solution, and the roots then absorb the nutrients from the soil-water. All plants have the same basic needs whether they are grown in soil or not. When the plant’s nutritional needs are met, soil is no longer necessary. In fact, the soil may harbor pathogens and other organisms that could harm the plant. In hydroponics, all the nutrients are supplied in a water solution that passes over the roots or floods around them at regular intervals. Plants often grow faster in a hydroponic system because nutrients are immediately available and therefore can be assimilated faster.Hydroponics2

When experimenting with hydroponics, as with all other gardening techniques, it is important that the gardener know the basic physiology of the plant that is, how the plant works. Plants use their roots to draw in water and minerals that are trans-ported upward into the leaves. They also take in oxygen and release carbon dioxide in respiration.

The leaves absorb energy during the day from sun-light and take up carbon dioxide from the air. The water from the roots, the carbon dioxide, and the light energy combine to form carbohydrates such as sugar. The plant then releases oxygen back into the atmosphere. These actions, aided by the nutrients gleaned from absorbed minerals, complete the process of photosynthesis, providing the energy and raw materials for growth. At night, the process reverses in the leaves. Carbohydrates break down, releasing the energy needed to create new leaves, stems, and roots, and carbon dioxide is released.

Hydroponics3Plants, much like human beings and animals, re-quire water, air, food, light, and warmth in order to perform these essential physiological processes and, as a result, to grow and reproduce. The basic hydroponic system should fill the needs of the plant’s roots just as the earth would by providing support, oxygen and carbon dioxide exchange (via the substrate), and water and nutrients (via the nutrient solution). Adequate light and warmth complete the minimal requirements for successful hydroponic plant growth.

Substrate

In order to serve as a suitable replacement for soil, the substrate must be capable of supporting the root system and holding moisture and nutrients. It should be inert, free of insects and diseases, and not easily broken down. Also, the substrate should allow adequate aeration of the roots and have good drainage qualities. Plants need sufficient access to oxygen in the air in order to grow and take up water and nutrients. Poor drainage can lead to de-creased growth, stunting, wilting, and discoloration of the leaves and, in the worst cases, “drowning.” Hydroponics4

Several commonly used substrates are coarse sand (ask for washed river sand), gravel, perlite, coarse vermiculite, and rock wool. Perlite and coarse vermiculite are good choices because they are sterile, uniform, and readily available in garden centers. Sand and gravel also work well but should be washed thoroughly before planting to remove lime or other impurities.

Water

Mature plants process a surprisingly large amount of water. For instance, a fully grown to mato plant may use up to 2⁄3gallon of water a day. An inadequate water supply is the most limiting factor to plant growth. Water deficiencies can cause the plant to spend all its available energy on developing an extensive root system, the result being a small, stunted shoot. For this reason, it is important that the media be flooded, and subsequently drained, one to three times daily or as often as necessary to keep the roots moist.

Light

The amount of light required varies from plant to plant. Most fruiting plants such as corn, tomatoes, and peppers need 8 to 10 hours of sunlight a day. If these plants are grown indoors, an artificial light must be used to provide high light intensity without causing the temperature to rise above acceptable levels. This situation may be difficult to achieve. On the other hand, many ornamental and foliage plants require less sunlight than fruiting plants do and therefore perform very well indoors. One common error in applying hydroponics is trying to grow plants in reduced light when full sun is required.

Temperature

Hydroponics5Warm-season plants perform best when the temperature is between 70 and 80 degrees F during the day and 60 to 70 degrees F at night. Cool-season plants generally require temperatures approximately 10 degrees lower than those suitable for warm-season plants. Above or below this range, plant growth will slow dramatically. Therefore, it is important that these temperatures be maintained whenever possible.

Nutrients

The key ingredient in the recipe for successful hydroponic gardening is the nutrient solution. In traditional soil-based gardening, the plant receives fertilizer from the slow breakdown of organic materials and the release of mineral nutrients in the soil. Hydroponic systems provide readily available, water-soluble minerals directly to the roots in a complete and balanced solution, thus eliminating the need for soil.

There are sixteen elements needed for plant growth. Plants extract several of these elements, such as oxygen, carbon, and hydrogen, from water and air. The rest of the elements must be supplied through the nutrient solution.

The primary macronutrients are nitrogen (N), phosphorus (P), and potassium (K). The secondary macro-nutrients are calcium (Ca), magnesium (Mg), and sulfur (S). These distinctions are made based on how much of each nutrient plants need. Micronutrients, or trace elements, such as iron (Fe), manganese (Mn), boron (B), molybdenum (Mo), zinc (Zn), copper (Cu), and chlorine (Cl) are used in very small amounts by plants, hence the name micronutrients. Micronutrients are sometimes present as impurities in the water and in the solid substrate.

Nitrogen

Nitrogen is central to the development of new leaves and stems as well as to overall growth and performance. An overabundance of nitrogen causes soft, weak growth and possible delay of fruit and flower production. Symptoms of nitrogen deficiency are yellowing leaves and weak, spindly growth.

Phosphorus

Phosphorus is used by the plant in photosynthesis and in the production of flowers and seeds. It also encourages strong root growth. When phosphorus levels are low, the older leaves begin to turn deep green and develop brown or purple dis-coloration. Other symptoms may be stunted growth and chlorosis, or yellowing, of the lower leaves.

Potassium

Potassium is necessary during all stages of growth, particularly during fruit development. It is involved in the manufacture of sugars, starches, and chlorophyll. Potassium helps the plant make good use of air and water by regulating stomatal openings in the leaves and also helps build strong roots. Deficiency symptoms are mottling and yellowing of older leaves, generally along the margins, and flower and fruit drop. Hydroponics6

Calcium

Calcium is used by the plant in the manufacture and growth of cells. It also acts as a buffer for excess nutrients in soil. Calcium deficiency is recognizable by the curling and stunting of young leaves and dieback of the shoot tip. Too much calcium can stunt the growth of a young plant.

Magnesium

Magnesium is fundamental in the absorption of light energy and is central to the structure of the chlorophyll molecule. Symptoms of magnesium deficiency include curled leaf margins, yellowing of older leaves (veins remain green), and, eventually, bright green coloration of the growing tips.

Nutrient Solutions

The elements needed for successful hydroponic growth are widely available in premixed form from gardening catalogs, garden centers, fertilizer companies, and hydroponic supply companies. Most hydroponics amateurs will rely on these commercially available mixes rather than preparing their own solutions at home.

However, for those enthusiasts who are willing to mix their own, the extra time and effort may offer more precise nutrient combinations for specific plants, as well as provide an opportunity for experimentation. Many nutrient solution recipes have been developed, some for general use and others for specific plants, and no one recipe is better for all plants than another. Hydroponic nutrient solutions contain several water-soluble, nutritive salts that can be purchased at fertilizer companies, green-house supply companies, and chemical companies.

The primary and secondary macronutrient salts are usually mixed in a large volume of water at a concentration ready to use on plants. The micronutrients are mixed as separate concentrated solutions that are then added in a measured amount to the macronutrient solution.

To make your own solution, mix 10 gallons of macronutrient solution according to the recipe in either Table 1 or Table 2. Nutrient solution No. 1 is more appropriate for slow-growing plants and plants growing under low light intensity, such as foliage plants. Nutrient solution No. 2 is more appropriate for rapidly growing plants and plants under high light intensity, especially vegetables. Next, mix the following two micronutrient solutions, and add each to the macronutrient solution.

• Mix 7.6 grams (11⁄4level teaspoons) of boric acid (H3BO4) and 0.6 grams (1⁄10teaspoon) of manganese chloride (MnCl2• 4H2O) in 1 quart of water.

Use 1⁄2cup of this solution for 10 gallons of macro-nutrient solution.

• Mix 3 grams (1⁄2level teaspoon) of chelated iron (NaFe EDTA) in 1 quart of water. Use 1 3⁄5cup of this solution for 10 gallons of macronutrient solution.

After mixing the nutrient solutions together, check the pH. (Meters for measuring pH can be purchased from garden and hydroponic supply companies.) Most plants grow well in a slightly acidic solution with a pH of 5.5 to 6.5. If the solution is too alkaline (pH greater than 7.0), add a few drops of white vinegar per gallon, stir, and recheck the pH. If the solution is to acidic, add a small amount of baking soda per gallon to increase the pH. Continue rechecking and making adjustments until the desired pH level is reached.

The nutrient solution can be reused for 10 to 14 days when applied one to three times a day. At the end of this period, flood the substrate with clean water and drain it several times to wash out any accumulated materials. Mix and add a new solution.

Simple Hydroponic Systems

The simplest hydroponic system for beginners is a non recycling system consisting of a well-drained container filled with an acceptable A larger-scale version of the recycling method involves using a container that has a hose and an outlet an inch or two from its base. The container must be raised off the floor and tilted so that the nutrient solution drains through the outlet into a receptacle. These simple hand-fed methods work best with small-scale systems. For larger systems, a submersible pump can be used to pump the solution back into the container from the receptacle substrate. The nutrient solution is mixed, and then it is applied one to three times daily, using a simple watering can. The excess solution drains away and is lost.

A more economical technique is the recycling method, which involves collecting and reusing excess solution. The simplest version of this technique involves placing a large dish under the plant container to catch the solution and then pouring the solution back over the plant at regular intervals.

In addition to the systems that require a substrate, there are non aggregate methods such as water culture and aeroponics. In water culture, the plant’s roots are kept submerged in the nutrient solution. The plants are supported by a grid of wire, rope, or string or by coarse screening. This method, however, introduces aeration problems and re-quires an aquarium pump to bubble oxygen into the nutrient solution.

One simple version of water culture for a single plant consists of using a pint- to quart-sized glass or plastic bottle or jar that has a stopper or lid with two holes in it. The stem of a young plant is passed through one hole so that the plant is held above the nutrient solution and the roots are in the nutrient solution. The plant’s stem is surrounded with cotton for support. The nutrient solution is aerated by an aquarium pump. The plastic tube from the pump is passed through the second hole in the lid and into the nutrient solution. The container is covered with aluminum foil to keep light off the root system.

In aeroponics, the plant’s roots are suspended in air and are regularly misted with a fine spray of nutrient solution. Misting must occur often enough to cover the roots with a constant film of nutrient solution at all times. The misting chamber must be kept dark so algae does not grow and compete with the roots. This method requires more mechanical and electrical sophistication than the previous methods do. The methods that use a substrate are generally less expensive, are easier to transplant from, and have fewer difficulties than the water or aeroponics methods do.

Getting Started

It is important that the beginner keep in mind that hydroponics is not the perfect solution to all gardening woes. There are pros and cons to both traditional soil-based gardening and hydroponics. One major disadvantage of hydroponics is the commitment of time and energy necessary for success. Soilless gardening is much more exacting than traditional gardening and may overwhelm the novice gardener if too complex a system is implemented.

Begin with a small project such as an herb garden to get a feel for hydroponics, and, as your knowledge and comfort increase, move on to a more elaborate system.

Source: Alabama Cooperative Extension System