Introduction to organic Agriculture

Organic Agriculture

• The term organic in chemistry refers to components containing the element carbon as an essential component, and refers to chemical components derived from living organisms of either animal or vegetable origin. Organic fertilizers are generally by-products of the processing of animal or vegetable substances that contain sufficient plant nutrients to be value of as a fertilizer without the need to add any synthetic materials.

• Organic Fertilizers - Should be 100% organic.

• Organic based Fertilizers – Blend of synthetic (in organic) as well as organic raw materials.

• Organic materials appear to be more ‘available’ to growing plants than inorganic materials, and do not leach as readily from the soil. This is thought to be due to the high cation exchange capacity of the organic matter in which nutrients are retained.

• Inorganic fertilizers because of its very nature of easy water solubility, when used in excess leads to heavy leaching of soluble phosphorus and nitrogen from the soil.

• Soil organic matter contains decomposed humus, decaying plant and animal matter and living soil organisms. Humus is a structure less colloidal matter resulting from the decomposition of any type of dead organic matter. It is a complex chemical mixture comprising proteins, lignin, fats, carbohydrates and organic acids. Humus is a storehouse of essential plant nutrients; including 95% of the Nitrogen 60% of the Phosphorus and 98% of the Sulphur available to plants. It has the ability to make some nutrients more soluble and available to plants because of increased activity by soil microorganisms.

• Always opt for organic based fertilizers because of their “slow release nature” resulting in minimum fertilizer wastage.

• Always apply Nitrogen in ammonium form rather than in nitrate form. Nitrogen in the ammonium form is attracted to and held by soil colloids and temporarily resistant to leaching. Plants can use Nitrogen in ammonium form but in most soils the ammonium form is gradually changed to the nitrate form before being taken up by plants. The conversion to nitrate form is more rapid where there is adequate air and moisture and where soils are warm. The change from ammonium form to the nitrate form, may take a few days to several weeks or months depending mainly on soil conditions, depth of application and temperature. This means that the nitrogen applied as ammonium form becomes available over a much longer period than is the case when nitrogen is applied in the nitrate form.

Soil Science - Basic Knowledge

S O I L S C I E N C E

As a tree grower we should have some basic knowledge about the chemical composition of our farm soil enabling us to select correct plant that suits our soil type. Some basic soil types, some problematic soils and their remedy methods are listed here.

Those who have already tested their farm soil and got test reports can verify their soil status with the following 'Soil quality parameter chart.'

S.No. ........ Parameter

1. pH range

Acidic : Below 6.5

Neutral : 6.5 to 7.5

Alkaline : above 7.5

2. E.C Electrical Conductivity should be less than 1.

3. Carbonate status:

P.E - Profuse effervescence

M.E - Medium effervescence

N.E - No effervescence

4. N.P.K
HighStatus ... MediumStatus........... LowStatus

N 148 ............ 113 to 148 .......... Below 113 Kgs per acre

P above 9 ...............4.5 to 9 .............Below 4.5 Kgs per acre

K above 113 ............ 48 to 113 .............Below 48 Kgs per acre

N Nitrogen – Essential for life

P Phosphate – P₂O₅ – Phosphate Pentoxide ( Key to yield)

K Potash – K₂ O – Potassium oxide ( Chemical Policeman)

( Na – Sodium is the thief.)

5. O.C Organic Carbon 0.5 – Good, 1 – Excellent

6. O.M Organic Matter Always double of O.C

Soil weight of 6” depth x 1 Acre area = 10 Lakh Kgs. In that mass if you add 200 tons of dry matter,You will get 20 tons of Organic matter (OM), that will give 10 tons of Organic Carbon (OC) that’s called 1% OC

7. C.E.C Cationic Exchange Capacity. It should be above 50. Achieving 100 is a must. Heavy dose of organic input and Humic acid will enhance CEC considerably.

8. Essential elements: Carbon, Hydrogen and Oxygen (available from air & water)

9. Major Nutrients: N P K

10. Secondary Nutrients: Ca, Mg and S

Ca – Calcium is the king among the nutrients. Among Ca, Mg, Na & K, more than 50% should be Ca. Ca content should be ¹/₃ to ¹/₂ of C.E.C. In other words Ca should be 50% of CEC. If Ca is low, then apply Calcium Carbonate. Application of Mono calcium Phosphate and Super Phosphate should be increased.

Mg - Magnesium should be 25% of CEC. Ca and Mg should be in the ratio of 3:1. If Mg is low, then apply MgSo₄.

Na, K and other Mineral balance 25% of CEC.

10 a) Micro Nutrients: Cu, Zn, Mn, Fe, Boron, Chlorine, Fluorine Etc.,

Cu - above 1.2 ppm or Kgs / Acre. If lower, then apply Cu So₄.

Zn - above 1.2 ppm or Kgs / Acre. If lower, then apply Zn So₄.

Mn - above 3.8 ppm or Kgs / Acre. i.e half the value of Fe. If lower, then apply Mn So₄.

Fe - above 6 ppm or Kgs / Acre. i.e double the value of Mn. If lower, then apply Fe So₄.

11. B.S.P: - Base Saturation Percentage should be above 80%.

Ratio between – (Ca + Mg + Na + K / (CEC) x 100 = 80%

12. E.S.P - Exchangeable Sodium Percentage.

Safe level below10

Moderate level 10 to 15.

Toxic level >15.

( Na / CEC) x 100 = below 10%

13. Types of Soil : Sand, Loamy Sand, Sandy Loam, Sandy Clay Loam, Clay loam, Sandy Clay, Silty Clay and Clay.

14. Ideal Soil Texture : Sand 33% : Silt 33% : Clay 33%

15. Acidic soil and its remedies: ( ‘அமில நிலம் ’ in Tamil)

Acidity due to Lower Ph because of low Ca.

pH range below 6.5 is Acidic.

Apply recommended dose of Calcium 10 days before applying any basal fertilizers then plough well to properly mix the Ca in the soil and irrigate.

16. Alkaline soil and its remedies: ( ‘களர் நிலம் ' in Tamil) Alkalinity due to higher pH because of the presence of Na.

Soil pH above 8 to 8.9 is Alkaline.

E.C below 4

E.S.P Below 10% (For Sodic Soil above 15%)

Growth of sensitive deep rooted crops will be moderately affected.

Apply liberal Qty. of FYM, raise Green Manure crops and plough them back into soil to increase O.C thereby increasing the drainage capacity of the soil.

Basal application of 300 Kgs of Gypsum per Acre for every crop. Apply more depending upon the alkalinity of the soil.

Use only Fertilizers like DAP, Zn So₄, Am So₄, K₂ So₄ (Pottassium Sulphate) Etc.

17. Sodic soil and its remedies: Presence of Na above 15 in Alkaline soil.

Soil pH above 9

E.C below 4

E.S.P above 15% (For Alkaline soils below 10%)

Sodium Carbonate in the Soil reacts with salts and Fertilizers and the end products get deposited as white patches above the soil.
Because of higher pH, nutrients in the soil are less. Since the soil subsurface is harder, plant roots can’t able to penetrate it.
Remedy for Sodic Soil:
Raise Daincha or Sunhemp and plough it back into soil (incorporate).

Cultivate Sun Flower Crop every year. It was proved that the Sun Flower plant absorbs Na from the soil and stores them in its parts. After harvest, the total plant with dried leaves should be removed.
Apply 5 Tons of press mud from Sugar mill.

Use only Fertilizers like DAP, Zn So₄, Am So₄, K₂ So₄ (Pottassium Sulphate) Etc.

Apply liberal Qty. of M.N nutrients especially Zn. (Zn So4 @ 40Kgs per Hect. as basal is necessary.

25% more N as Basal is necessary.

Raise Saline resistant varieties (Such as Trichy 1, Co 43 in Paddy)

For Paddy, transplant only matured plantlings of 35 to 40 days age. Plant 3 to 5 saplings per Kuthu. Sodic condition can be rectified using Chemicals such as Gypsum, Sulphur or Pairates.

Role of Gypsum (Ca So₄) in the reclamation of Sodic Soil:

Contents of Gypsum: S 18% + Ca 23% + P2 O5 5%

Regular application of Gypsum (Ca So₄) @ 200 Kgs per Acre will give good yields because of it’s S and Ca contents.

It neutralizes the harmful Na in the soil and reduces the E.S.P.

For Sodic soil reclamation :

1) Deep plough the field twice especially by Disc plough. It breaks open the hard soil pan lies in the subsurface and brings out the Na rich soil to the surface.

2) Evenly spread Gypsum (Ca So₄) 2 Tons – leading in good quality water (leaching) – puddling by cage wheel ( தொலியடிப்பு ) - maintain Water level at 6’’ and wait for 2 days. - Ca So₄ in Gypsum reacts with Na ( Sodium Bicarbonate ) in the soil and becomes Na So₄ – Drain out the frothy Na So₄ solution from the field. – Irrigate immediately - puddling by cage wheel ( தொலியடிப்பு) 2^nd time – Drain out the frothy Na So₄ solution from the field.

3) Raise Daincha and incorporate. 4) Afetr that raise ‘Horse Gram’ ( “கானம் ” in Tamil) and don’t take seeds in the first year – allow the seeds to drop and the plant to wither – after the rains i.e. in the next season take seeds.

Saline soil and its remedies: ( ‘ உவர் நிலம்’ in Tamil)
Normal Ph range, but with more E.C, because of Sulphates and Chlorates of Ca, Mg, Na and K.

Soil with high soluble salts, hence E.C above 4

Density of the cell sap in the root system is lower than the density of the salts in the soil resulting in reverse osmosis. (i.e) water / cell sap will ooze out of the cell wall and into the soil.

Cultivate Saline (Uvar) tolerant varieties such as Paddy , Ragi, Cotton, Sugar cane and Chillies,

Apply liberal Qty. of FYM, raise Green Manure crops and plough them back into soil to increase O.C thereby increasing the drainage capacity of the soil.

Level the field evenly - Irrigate Soft water ( free from Bicarbonates) copiously – maintain water level – then drain out the water completely - the unwanted salts dissolves in the water and flows out.

Provide adequate channels to let in rainwater and water from the irrigation tank. Salts will be washed off during heavy rains. Drain out the salt dissolved water from the field. We can reduce the salt content of the soil by increasing the drainage capacity of the field.

Botanical and Vernacular names of Trees

No. Botanical Name .........Vernacular Name ...............Tamil Name

Acacia Auriculiformis ......... Pencil Tree ......... Kathi Savukku, Kathi Karuvel, Elai Karuvel.
Acacia Mangium ......... Maan Sevi Karuvai
Acacia Leucopholea ......... Velvael
Acacia Planiferns .......... Kudai Vel, Udai Mul
Acacia Arabia .......... Babul ............ Karuvel
Acacia Nilotica .......... Babul ............ Karuvel
Prosopis Juliflora - Seemai Karuvel, Vaeli Karuvel, Vaeli Kathaan, Seemai Udai
Adina Cardifolia ......... Manja Kadambu
Anthocephalus Indicus /
Anthocephalus cadamba .......... Vellai Kadambu
Aegle Marmelos ......... Vilvam
Ailanthus Excelsa .......... Perumaram, Peemaram
Sterculia Foetida .......... Wild Almond, Poon ..... Peenari, Paei Elavam
Albizzia Amara ........... Usila Maram
Albizzia Lebbeck .......... East Indian Walnut ......... Vagai
Albizia Falcataria .......... Kattumaram
Albizzia Odoratissima ....... Sila Vagai
Gmelina Arborea .......... Kumil, Kumul
Melia Dubia ........... Malabar Neem Wood ........ Malai Vembu
Azadirachta Indica ......... Vembu
Toona Ciliata ......... Santhana Vembu
Casuarina Junghuhniana .......... Indonesian Savukku, Junguniana Savukku
Cassia Siamea .......... Manja Konrai, Panni Vagai
Grewia Tiliaefolia ........... Thadasu, Sadachi, Valukkai, Unnu
Khaya Senegalansis ......... Kaya Maram (Grow upto 15 m Ht. Gives high quality wood)
Memecylon umbellatum ...... Kaya Maram (Small tree, grow upto 5m only)
Memycylon edule .......... Kaya Maram
Swietenia Macrophylla ...... Peruvian Mahogany
Swietenia Mahogany .. Jamaican Mahogany ...
Pterocarpus Santalinus ... Red Sanders ... Sivappu Santhanam, Santhana Vengai
Pterocarpus Marsupium .......... Indian Kino Tree ......... Vengai
Dalbergia Sissoo.....Indian Rose Wood .......... Sisu
Dalbergia Latifolia ..... East Indian Rose Wood .......... Thothakathi
Dalbergia Paniculata ....... Pani Vagai

( To continue )

Grewia tiliifolia (Tamil: Thadasu)

Name of the plant - Grewia tiliifolia (Tamil: Thadasu, Sadachi, Valukkai, Unnu)



‘N’ fixing capacity - NO

Fodder Tree - Yes, Nutritious

Deciduous - Yes

Drought tolerance - Yes

Soil type / pH range - Red soil, Mixed soil

Tolerance to water logging - NO

Seeds - 5 to 20 seeds / gm.

Germination - 73%

Vegetative propagation - Possible

Spacing for border planting- 3 m
For bulk planting - 6 m x 6 m

Maturity Years - 15? - 20? years

Growth : Height - 12 – 15 m Ht
Girth - 1.3 m at basal

Yield - 5 Sq.m / Hect / Year

Timber Density - 0.72, Hard wood, Black colour heart wood
Weight - 734 Kgs./ Sq.m

Uses - For furniture,

Ratoon - Poor, not recommended.

Special features if any - Tree with thick canopy. Performs well in irrigated lands. One of the fastest growing trees. Timber is amenable to carpentry works so it fetches good price.