Nutrient Mobility in Plants

18 elements have been identified as vital to plant growth. 

3 elements, carbon, hydrogen and oxygen, are non-minerals.  Carbon and oxygen enter plants through leaves as carbon dioxide. Oxygen also enters plants with hydrogen through roots as water.

14 are minerals. The 14 must be dissolved in soil water and enter the plant as roots take up water. Mineral elements can further be divided into primary or secondary macronutrients and micronutrients. 

Macronutrients are those needed in relatively large amounts while micronutrients, as their name implies, are needed in small amounts. However, a deficiency in any vital element can seriously inhibit plant development.

Once inside plants, nutrients are transported to where they are needed. Once incorporated by the plant, some elements can be immobile while others can be remobilized. 

Immobile elements essentially get locked in place. Those that can be remobilized can leave their original location and move to areas of greater demand.

Availability of Nutrients to Plants at Different pH Levels

Plant Growth : Nutrients

Essential elements

Carbon 碳 ( C ) , Hydrogen氢 ( H ) ,& Oxygen 氧 ( O).

Essential elements ( Arnon and Stout, 1939) :

-        A plant must be unable to complete its life cycle in the absence of the mineral element.

-        The function of the element must not be replaceable by another mineral element.

-        The element must be directly involved in plant metabolism.

Macronutrients ( 大量元素):
Primary : Nitrogen氮(  N ) , Phosphorus磷( P ) , Potassium鉀( K )
Secondary : Calcium钙( Ca ) , Magnesium鎂( Mg ) ,&  Sulfur硫( S ).         

Macronutrients are consumed in large quantities.  They are present in plant tissue in quantities from 0.2% - 4%.

Micronutrients ( 微量元素 ) ( Trace elements ) :

Chlorine 氯( Cl ) , Iron 铁( Fe ) , Manganese 锰( Mn ) , Boron 硼( B ) , Zinc 锌( Zn ) , Copper 铜( Cu ) , Molybdenum 钼( Mo ) & Nickel 镍( Ni ).  

Micronutrients are present in plant tissue in small quantities.

Beneficial Elements :

Silicone 硅 ( Si ) ,&  Cobalt 钴 ( Co ).   

Beneficial elements are those that  :

-        can compensate for toxic effects of other elements or

-        may replace mineral nutrients in some other less specific function e.g. the maintenance of osmotic pressure.

The omission of beneficial nutrients in commercial production could mean that plants are not being grown to their optimum genetic potential but are merely produced at a subsistence level.

The beneficial elements have not been deemed essential for all plants but may be essential for some.

 

e.g. Cobalt is essential for nitrogen fixation in legumes. It may also inhibit ethylene formation ( Samimy, 1978 ) and extend the life of cut roses ( Venkatarayappa et al., 1980 ).

e.g. Silicon is deposited in cell walls, has been found to improve heat and drought tolerance and increase resistance to insects and fungal infections. Silicon can help compensate for toxic levels of manganese, iron, phosphorus and aluminum as well as zinc deficiency.

Types of Fruits ( Botanical )

1. Simple fruit, fleshy ( develop from a simple or compound ovary with only one pistil ) :

· Berry

- develop from a single ovary, ovary ripens into edible pericarp.

- eg. Avocado, Barberry, Buah, Melaka, Current, Chili, Ciku, Eggplant, Elderberry, Gooseberry, Grape, Guava, Honeysuckle, Kiwi, Mayapple, Nannyberry, Oregon-grape, Pomegranate, Tomato, Sea-bcukthorn, Starfruit

Hesperidium

- modified berry

- eg. Orange, Kumquat, Lemon

Pepo

- modified berry

- eg. all Cucurbitaceae ( Cucumber, Pumpkin, Squash, Watermelon ), Passiflora, Carica

· Epigynous / False Berry

- an accessory fruit, developed from flowers with inferior ovary. some or all of the flesh is derived not from the ovary but from some adjacent tissue.

- eg. Banana, Blueberry, Cranberry

· Drupe

- develop from a single carpel, mostly from flowers with superior ovaries ; endocarp with seed inside, surrounded by fleshy mesocarp and endocarp

- eg. Coffee, Jujube, Longan, Lychee, Mango, Olive, most Palms ( Date, Oil Palm ), Pistachio, Rambutan, all Prunus ( Almond, Apricot, Cherry, Damson, Nectarine, Peach, Plum )

· Pome

- An accessory fruit developed from one or more carpels, surrounded by accessory tissue

- all Maloideae of Rosaceae ( Apple ), Pear 

2. Simple fruit, dry

a. Dehiscent

Capsule

- developed from two or more carpels

- eg. Brazil nut, Cotton, Durian, Lily, Orchid, Poppy.

Follicle

- developed from 1 carpel; many-seeded dry unilocular fruit

- eg. Larkspur, Magnolia, Banksia, Peony, Milkweed

Legume

- developed from a simple carpel ; fruits usually called a pod

- eg. Alfalfa, Clover, Peas, Beans, Lentils, Lupins, Mequited, Carob, Soy, Peanuts

Loment

- eg. member of genus Desmodium and Hedysarum of Fabaceae

Schizocarp

- developed from multiple carpels

- eg. members of Geranium

b. Indehiscent

Achne

- developed from a single carpel, contain a single seed that nearly fills the pericarp, but does not adhere to it.

- Eg. Buttercup, Buckwheat, Dandelion, Sunflower

Caryopsis

- developed from a single carpel, resembles an achene, except that in caryopsis the pericarp is fused with the thin seed coat

- eg. Corn, Rice, Wheat

Dry drupe

- sometime fibrous

- eg. Coconut

Nut

- developed from pistils with inferior ovaries ; ovary wall becomes very hard at maturity, seed remains unattached with the ovary wall.

- eg. members of family Fagales ( Chestnust, Hazel )

Samara

- winged achne

- eg. Maple

Shizocarp

- developed from multiple carpels

- eg. Carrot, member of genus Abutilon, Malva, Malvastrum, Sida

Silique

- fruits of 2 fused carpels that separated when ripe

- eg. many members of Brassicaceae family

3. Compound - Aggregate fruit

- aggregates of small, individual fruits, each fruitlets develop from a single flower with multiple carpels

- aggregate of achenes, eg. Strawberry

- aggregate of drupes, eg. Blackberry, Raspberry

- aggregate of samaras, eg. Tuliptree

- aggregate of capsules, eg. Sweet gum

- aggregate of follicles, eg. Magnolia

4. Compound - Multiple fruit

- aggregates of small, individual drupes. Each drupelets develop from a different flower, from a cluster of flowers
- eg. Cempedak,  Fig, Jakefruit ( Nangka ), Mulberries, Pineapple, ¿ Soursop, ¿ Nona, Noni

Organic Farming - Methods

"An organic farm, properly speaking, is not one that uses certain methods and substances and avoids others; it is a farm whose structure is formed in imitation of the structure of a natural system that has the integrity, the independence and the benign dependence of an organism"
Wendell Berry "The Gift of Good Land"


Organic farming is a production system which favors maximum use of organic material and discourage use of synthetically produced agro-inputs, for maintaining soil productivity and fertility and pest management under conditions of sustainable natural resources and healthy environment.

Soil Management

Plants rely primarily on soil for water and nutrients. It is therefore soil health is utmost important for organic farmers. But providing adequate nutrients is often a challenge.

Crop rotation, green manure, intercropping, cover cropping, mulching etc., help to provide nutrient to the soil, as well as increasing the soil’s organic matter. Certain processed fertilizers such as seed meals, compost, bloodmeal, animal excreta, naturally-occurred-fertilizer, eg. rock phosphate and limestone are used. Altogether these methods help to control erosion, promote biodiversity, and enhance the health of the soil.

Weed Control

Weed control is the botanical component of pest control, stopping weeds from reaching a mature stage of growth when they could be harmful to domesticated plants and livestock.

Typically, a combination of methods is used in organic farming. The most basic is manual weeding, with hand or aided with some simple tools. Flaming, a traditional technique is sometime used, but subjected to local legislation. Mechanically tilling and ploughing, are effective ways to control weeds, were however involve diesel-powered tractor, unfortunately which is not an environmental-friendly machine. Other techniques for controlling weeds include mulch, solarization, crop rotation, drip-irrigation ( limit weeds access to water ) natural pre-emergence herbicide ( e.g. corn gluten meal, garlic, clove oil, borax, pelargonic acid, table salt, vinegar, and various other homemade remedies).

Control Other Organisms

Organisms aside from weeds which cause problems include athropods (e.g. insects, mites) and nematodes. Fungi and bacteria can cause disease.
Insect pests are a common problem, and insecticides, both non-organic and organic, are controversial due to their environmental and health effects. One way to manage insects is to ignore them and focus on plant health, since plants can survive the loss of about a third of lead area before suffering severe growth consequences.

To avoid using insecticides, one can select naturally-resistant plants, put bags around the plants, remove dying material such as leaves, fruit, and diseased plants, covering plants with a solid barrier ("row cover"), hosing, encouraging and releasing beneficial organisms and beneficial insects, planting companion plants and polycultures, various traps, sticky cards and season extension. Biological pest control uses natural predators to control pests. Recommended beneficial insects include minute pirate bugs, big-eyed bugs, ladybugs, lacewings, parasitoid wasps, praying mantis and predatory mites.

Several of pesticides approved for organic use have been called green pesticides such as spinosad and neem. Generally, but not necessarily, organic pesticides are safer and more environmentally friendly than synthetic pesticides. The main three organic insecticides used are Bt (a bacterial toxin), pyrethrum and rotenone. Nicotine sulfate may also be used; although it breaks down quickly, it is extremely toxic, nearly as toxic as aldicarb. Less toxic but still effective organic insecticides include neem, spinosad, soaps, garlic, citrus oil, capsaicin (repellent), Bacillus popillae, Beauvaria bassiana, and boric acid. Pesticides should be rotated to minimize pest resistance.

The first disease control strategy involves keeping the area clean by removing diseased and dying plants and ensure that the plants are healthy by maintaining water and fertilization. Polycultures reduce the ability of disease to spread. Disease-resistant cultivars can be purchased. Organic fungicide include the bacteria Bacillus subtilis, Bacillus pumilus, and Trichoderma harzianum which are mainly effective for diseases affecting roots. Bordeaux mix, sulfur, lime sulfur, potassium and sodium bicarbonate can be used as an organic fungicide in various forms