Zinc: Importance and Current situation

Zaghum Sattar & Abdul Saboor Butt

Institute of soil & Environmental Sciences, University of Agriculture, Faisalabad

Zinc (Zn) is among those minerals that were first considered as essential for plants, animals and human. Zn is a basic essential trace mineral element for normal healthy growth in plants, animals and humans that uptake as a divalent cation (Zn²⁺) by plants. Zn is playing principal metabolically role in plants and required in the carbonic enzyme present in all photosynthetic tissues, and also required for chlorophyll biosynthesis. Zinc is one of the essential micronutrient for the normal healthy growth and reproduction of crop plants. Zn plays an important role in plant metabolism by influencing the activities of enzymes, hydrogenase and carbonic anhydrase, stabilization of ribosomal fractions and also synthesis of cytochrome.  Zn also activate plant enzymes involved in carbohydrate metabolism, integrity maintenance of cellular membranes, synthesis of nucleic acids and specific proteins, regulate auxin synthesis and pollen formation. The regulation of the gene expression required for the tolerance of environmental stresses in plants also depend on the Zn.Zinc deficiency involves in the abnormalities development in plants as deficiency symptoms such as stunted growth, chlorosis and smaller leaves, spikelet sterility. Zn deficiency can also adversely affect the quality of harvested products; plants susceptibility to injury by high sunlight or temperature intensity and to infection by fungal diseases can also increase. A zinc deficiency affects the capacity for water uptake and transport in plants. Zn involves in the synthesis of tryptophan which is a precursor of IAA, and in the production of growth hormoneauxin. Zinc deficiency is common in humans, animals and plants. More than 30% world’s population suffers from Zn deficiency. Zinc deficiency is found to be more common in developing countries due to low Zn in their diet. Zinc plays a part.in the basic roles of. Cellular functions in all living organisms and also involved in the human immune system. The optimum dietary intake for human adults is 12-15 mg Zn per day. Zinc acts as a catalytic or structural component in various body enzymes.Unsatisfactory intake and improper absorption of Zinc in the body may cause deficiency of Zn.  Zn malnutrition in humans can result in many fatal and other diseases like hair and memory loss, skin problems and weakness in eye side and body muscles. Insufficient intake of Zn during pregnancy in women also causes stunted brain development of the fetus. Infertility has also been observed in Zn deficient men. Zinc deficiency may cause congenital diseases like Acrodermatitis enteropathica. According to FAO/WHO recommendations an average male need 11 mg of Zn daily while an average female needs 9 mg of Zn. During pregnancy and lactation, the female needs 13 mg to 14 mg of Zn daily. Infants from 7 months to 3 years need 3 mg, 4 to 8 years need 5 mg and children from 9 to 13 years need 8 mg of Zn daily. In Pakistan, Zn deficiency is common in children and in women.Trace elements such as Zn are contained in all soils in measurable amounts. However, these concentrations can vary considerably. The overall mean total Zn concentration in soil is around 55 mg Zn kg^-1. A typical range of Zn in soils is from 10 to 300 mg Zn kg^-1. These values do not include contaminated soils, which may have much higher zinc concentrations.However, plant available Zn is very low as compared to its total amount. For a better Zn nutrition of human beings, cereal grain should contain around 40-60 mg Zn kg^-1 where current situation is 10-30 mg Zn kg^-1. Soils with low zinc availability for plant uptake represent nearly half of the cereal-growing areas of the world. The countries most affected by zinc deficient soils are Pakistan, India, Iran, China and Turkey with 50-70% of arable land classified as zinc deficient.

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Soil Sampling

Soil testing is the single most important guide to the profitable use of fertilizer and lime. It is in the best interest of farmers, lawn care professionals, landscapers, gardeners, fertilizer suppliers, and consultants to promote the use of soil testing for several reasons like

• Grow Higher Crop Yields
• Produce Higher Quality Crops And Ornamentals
• Use Fertilizer Dollars More Efficiently

The purpose of soil testing is to identify the soil fertility that the plants or crop, in a given area will experience. The soil area and volume could be a large field, a small garden, or simply the root zone of a single tree or shrub. The most difficult step in soil testing is accurately representing the desired area of soil. A laboratory cannot improve the accuracy of a sample that does not represent the area.

In most soils, it takes more than one year to make significant changes to the soil test levels. As the soil improves with better fertility programs, subsequent crops or plant growth should show increasing rates of improvement. Soils are formed over thousands of years, and are not easily changed in a short time.

Sampling Tools

Tools that may be used to take a sod sample include a spade or shovel, soil sampling tube, or soil auger. Sample tubes or augers should either be stainless steel or chrome plated.

When sampling various soils at different times of the season it is important to use the proper equipment. A soil probe, either a hand tube or hydraulic probe, can be used under most conditions. A small wooden rod may be helpful in removing the soil core from the tube. The soil auger is especially useful when sampling frozen ground or heavily compacted soil that a soil tube can't penetrate. If a spade is used for sampling, dig a V-shaped hole to sample depth; then cut a thin slice of soil from one side of the hole. if using a pail to collect the soil, it should be plastic to avoid any contamination from trace metals. For instance, soil will pick up zinc from a galvanized pail. When sampling wet soils, vegetable oil or mineral oil may be used to lubricate the probe to minimize soil pushing ahead of the probe.

A Few Universal Basics

1. Soil samples can be taken with a professional soil probe, or simply using a shovel, spade, or garden trowel.

2. Each sample should be composed of from 10 to 15 cores.

3. As you take cores of soil, put them into the plastic bucket. Mix the soil thoroughly in the bucket (galvanized buckets will contaminate the sample with zinc), breaking up all cores. Then, fill the soil bag to the green line (about 1 cup of soil). Discard any extra soil.

Soil Sampling Procedure:

1. Samples are taken separately and away from the road side and heaps of the fertilizers or farm yard manure.

2. Take first sample of the soil with the Augar or shovel/spade at the depth of 0 to 15 cm.

3. Take second sample at the depth of 15 to 30 cm.

4. Similarly further samples will be taken from the selected are in the field.

5. Put the simples of soil in the buckets depth wise.

6. Note soil depth with the help of marker on polythene plastic bags.

7. Dry the samples at optimum sun shine.

8. Now store the sample for further analysis.

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Nitrogen Fertilizers Used Off-Season Help Crops Planted Later

Oct. 7, 2008 — Combating soil erosion is a primary concern for agricultural producers in the United States, and many have incorporated conservation tillage systems in their effort to maintain a profitable crop output.

Cover crops are an important tool in this cycle, and while it is known that using nitrogen fertilizers can increase these crops biomass, the resulting levels of nitrogen for the following cash crops have been unknown.

Researchers found that areas that did have fertilizer applied to their cover crops had less biomass output for soil protection, while plots that did use fertilizer had greater biomass along with an increased amount of nitrogen available for the cash crop.

“Use of high-residue cover crops is imperative to prevent soil erosion, to bank leftover nutrients during the winter for summer cash crops, and to improve soil quality,” said Mark Reiter, lead author of the study. “From this data we see that we can increase cover crop biomass by using nitrogen fertilizer and that the nitrogen will later be available to our cash crop. It is a win-win situation.”

The study was conducted by USDA-ARS scientists with the Conservation Systems Research Team in Auburn, AL and the J. Phil Campbell Senior Natural Resource Conservation Center in Watkinsville, GA, in cooperation with Auburn University. Scientists investigated the effects of using nitrogen fertilization on rye cover crops, as well as the subsequent fertilizer availability to cotton.

The focus of the study was on plots in the Tennessee Valley Region of northern Alabama, which is a highly productive region in the nation’s Cotton Belt. To study the effects of fertilizer, rye cover crops were varied in the amount of nitrogen used.

After the rye had dried up, cotton was planted in the same soils and fertilized with different amounts of nitrogen. Researchers collected the plant and soil samples and determined how much nitrogen had been integrated into the plant and soil systems. A nitrogen isotope was used to trace the nitrogen used in the fertilizer, as opposed to nitrogen that is native to those soils.

While the results of the study are positive to understanding conservation tillage, further research is still needed before establishing new fertility management guidelines in all crops using high-residue cereal cover crops. In applying this research, it is expected that soil quality, along with management of the nutrients in the soil, will improve the success of American agricultural producers.

Story Source:

The above story is reprinted from materials provided by Soil Science Society of America.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.

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Journal Reference:

1. Reiter et al. Cotton Nitrogen Management in a High-Residue Conservation System: Cover Crop Fertilization. Soil Science Society of America Journal, 2008; 72 (5): 1321 DOI: 10.2136/sssaj2007.0313

Website Source: http://www.sciencedaily.com/releases/2008/10/081001125958.htm

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Pomegranate:Cultivation and Farming

Pomegranate

(Punica granatum)

Cultivation and Farming

Pomegranate Cultivation Farming Soils and Climate

 

Soil - Pomegranates are fairly drought tolerant and can be grown on either calcareous or acid soils. Climate - Grow best in dry climates with mild winters. Chilling requirement - Unclear; can be grown in tropical climates without chilling. Cold hardiness - Wood tolerates temperatures down to -11°C.

 

The pomegranate thrives on calcareous, alkaline soil and on deep, acidic loam and a wide range of soils in between these extremes

 

Propagation

 

Pomegranate seeds germinate readily even when merely thrown onto the surface of loose soil and the seedlings spring up with vigor. However, to avoid seedling variation, selected cultivars are usually reproduced by means of hardwood cuttings 25-50 cm long. Treatment. indole-butyric acid and planting at a moisture level of 15.95% greatly enhances root development and survival. The cuttings are set in beds with 1 or 2 buds above the soil for 1 year, and then transplanted to the field. Grafting has never been successful but branches may be air-layered and suckers from a parent plant can be taken up and transplanted.

 

Pollination

 

The pomegranate is both self-pollinated and cross-pollinated by insects. There is very little wind dispersal of pollen. Self-pollination of bagged flowers has resulted in 45% fruit set. Cross-pollination has increased yield to 68%. In hermaphrodite flowers, 6 to 20% of the pollen may be infertile; in male, 14 to 28%. The size and fertility of the pollen vary with the cultivar and season

 

Cultivar

 

Types with relatively soft seeds are often classed as "seedless". Among the best are 'Bedana' and 'Kandhari'. 'Bedana' is medium to large, with brownish or whitish rind, pulp pinkish-white, sweet, seeds soft. 'Kandhari' is large, deep-red, with deep-pink or blood-red, subacid pulp and hard seeds. Others include:

 

'Alandi' ('Vadki')–medium-sized, with fleshy red or pink, subacid pulp, very hard seeds.

 

'Dholka'–large, yellow-red, with patches of dark-pink and purple at base, or all-over greenish-white; thick rind, fleshy, purplish-white or white, sweet, pulp; hard seeds. The plant is evergreen, non-suckering, desirable for commercial purposes

 

'Kabul'–large, with dark-red and pale-yellow rind; fleshy, dark-red, sweet, slightly bitter pulp.

'Muscat Red'–small to medium, with thin or fairly thick rind, fleshy, juicy, medium-sweet pulp, soft or medium-hard seeds. The plant is a moderately prolific bearer.

 

'Paper Shell'–round, medium to large, pale-yellow blushed with pink; with very thin rind, fleshy, reddish or pink, sweet, very juicy pulp and soft seeds. Bears heavily.

 

'Poona'–large, with dark-red, gray or grayish-green rind, sometimes spotted, and orange-red or pink-and-red pulp.

 

'Spanish Ruby'–round, small to medium or large; bright-red, with thin rind, fleshy, rose-colored, sweet, aromatic pulp, and small to medium, fairly soft seeds. Considered medium in quality.

 

'Vellodu'–medium to large, with medium-thick rind, fleshy, juicy pulp and medium-hard seeds.

'Muscat White'–large, creamy-white tinged with pink; thin rind; fleshy, cream-colored, sweet pulp; seeds medium-hard. Bears well. Desirable for commercial planting in South Africa

 

Culture

 

Rooted cuttings or seedlings are set out in pre-fertilized pits (60 cm) deep and wide and are spaced 3.5-5.5 m apart, depending on the fertility of the soil. Initially, the plants are cut back to 60-75 cm in height and after they branch out the lower branches are pruned to provide a clear main stem. Inasmuch as fruits are borne only at the tips of new growth, it is recommended that, for the first 3 years, the branches be judiciously shortened annually to encourage the maximum number of new shoots on all sides, prevent straggly development, and achieve a strong, well-framed plant. After the 3rd year, only suckers and dead branches are removed. For good fruit production, the plant must be irrigated.

 

Pests and Diseases

 

Pomegranate butterfly, Virachola isocrates, lays eggs on flower-buds and the calyx of developing fruits; in a few days the caterpillars enter the fruit by way of the calyx. These fruit borers may cause loss of an entire crop unless the flowers are sprayed 2 times 30 days apart. A stem borer sometimes makes holes right through the branches. Twig dieback may be caused by either Pleuroplaconema or Ceuthospora Phyllosticta. Discoloration of fruits and seeds results from infestation by Aspergillus castaneus. The fruits may be sometimes disfigured by Sphaceloma punicae.

 

Dry rot from Phomopsis sp. or Zythia versoniana may destroy as much as 80% of the crop unless these organisms are controlled by appropriate spraying measures. Excessive rain during the ripening season may induce soft rot.

 

Minor problems are leaf and fruit spot caused by Cercospora, Gloeosporium and Pestalotia sp.; also foliar damage by whitefly, thrips, mealybugs and scale insects; and defoliation by Euproctis spp. and Archyophora dentula. Termites may infest the trunk.

 

Training Young Trees

 

Trees may be trained to a bush, single- or multiple-trunked tree. The bush form is satisfactory for backyards or hedgerows, but is undesirable for good commercial production.

 

Trees form the nursery are planted bare root in winter or early spring. The natural growth habit of the pomegranate is to produce many suckers from the base of the tree. If a single truck tree is desired, only one vigorous sucker or the trunk of the original nursery tree should be selected and branches grown from it. Basal suckers should be removed periodically to promote growth form the main trunk of the newly planted tree. If the orchard trees are to be developed into a multiple-trunk system, five or six vigorous suckers should be selected around the base of the young tree and allowed to grow.

 

Selection of the five or six suckers to be developed into permanent trunks may take two or three or more years until good trunks are correctly positioned to form a sturdy and symmetrical tree. All other suckers should be removed in summer and during dormant pruning.

 

Many growers prefer the multi-trunk system. In case of frost injury, usually only one or two trunks are injured, leaving the others to continue bearing. New trunks can be trained from suckers and full production restored to the tree in 2 or 3 years. Single-trunked trees may be completely killed except for suckers coming form the ground. Trees trained to a multiple truck require less frequent care in pruning during the first few years and come into bearing sooner than trees having only one truck.

 

Some pruning and tying with ropes for support may be needed for the first 3 or 4 years or until trunks are large and rigid enough to support the developing top.

 

Pruning

 

Pomegranate trees require a small amount of pruning each winter to maintain shape and good bearing surface. Even mature trees grow vigorously, sending up a large number of shoots and basal suckers that require removal each year.

 

The short spurs on 2- or 3-year-old wood growing mostly on the outer edge of the tree produce flowers. These spurs develop on slow growing, mature wood that bears fruit for several years, but as the tree increases in size the wood loses its fruiting habit. Light, annual pruning encourages growth of new fruit spurs and heavy pruning reduces yields. Care should therefore be taken to leave adequate fruit-bearing wood on the tree, while removing crossing over or interfering branches. In addition, some thinning out of crowded bearing areas helps produce larger fruit having fewer wind scars.

 

Should below-freezing temperatures occur in early winter before trees are fully dormant, or in early spring when trees are beginning to leaf out, severe damage can be done to tree trunks. Occasionally, entire trunks are girdled and killed by frost. Remove weak or dead limbs during the next growing season, and permit a vigorous sucker to develop from ground level to replace it.

 

Fertilization

 

Mature pomegranate trees require from 1-2kg of actual nitrogen per tree per year. This may be applied in one application in fall or winter. On light soils a split application may be desirable, one-half of the fertilizer being applied in late winter and the remainder in spring. Excessive or late applications of nitrogen may delay fruit maturity and color. Some evidence indicates that excessive nitrogen applications cause increased vegetative growth and reduce fruit production.

 

There is not evidence to show that phosphorous (P) or potassium (K) will improve growth or fruit quality when used to fertilize pomegranate orchards. Occasionally, zinc deficiency is evident in trees. This is corrected by applying zinc sprays during the dormant season or to the foliage in spring and early summer.

 

Irrigation

 

The pomegranate can withstand long periods of drought. Although not much fruit is produced under drought conditions, trees will survive for years; then, if properly irrigated, they grow vigorously and produce good crops.

 

Trees will thrive and produce an abundance of fruit under high summer rainfall conditions but the fruit tends to be soft and has poor shipping and storage quality.

 

To produce large crops of good-quality fruit, pomegranates require about the same amount of water and frequency of application as citrus. Adequate soil moisture must be maintained throughout the growing season, particularly as harvest approaches in late summer and early fall, when it helps reduce the number of split fruit.

 

Most orchards are irrigated under the furrow system, but sprinkler and drip irrigation systems are satisfactory if properly designed. Orchards thrive under noncultivation and semi-noncultivation systems. Weed control is difficult because at present no pre-emergence herbicides are registered for use in pomegranate orchards.

 

 

Harvesting and Yield

The fruits ripen 6 to 7 months after flowering. The fruit cannot be ripened off the tree even with ethylene treatment. Growers generally consider the fruit ready for harvest if it makes a metallic sound when tapped. The fruit must be picked before over maturity when it tends to crack open if rained upon or under certain conditions of atmospheric humidity, dehydration by winds, or insufficient irrigation. Of course, one might assume that ultimate splitting is the natural means of seed release and dispersal.

 

The fruits should not be pulled off but clipped close to the base so as to leave no stem to cause damage in handling and shipping. Appearance is important, too much sun exposure causes sunscald–brown, russeted blemishes and roughening of the rind.

 

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