ORGANIC FARMING – A CLEAR PERSPECTIVE K.Periasamy M.Tech(Chem Engg), Chennai - 96The Plants need Carbon( C ), Nitrogen(N), Phosphorous (P), Potassium (K), Hydrogen (H), Oxygen(O),Magnesium(Mg), Sulphur (S) for their growth. They also need several micro nutrients likeManganese(Mn), Calcium(Ca), Zinc(Zn), etc depending upon the plant type and the products that theyyield. Let us see the role of each element and its source for the plants.Carbon (C) - Carbon has two important roles. One is that it is part of the body of the plant itself – it is the major building block of Cellulose and Lignin which constitute any Plant. The other is that, its presence in top soil as Soil Organic Carbon (SOC). This is essential for the growth of microorganisms, which in turn facilitate the biological activity of Plant growth. - Carbon for the first part – Body of the plant is derived from two sources and both are required. Either alone will not work – (1) From the CO 2 absorbed by the leaves from Air (2) From the Carbon compounds (Organic Acids) available in the soil. The first is naturally available in atmosphere and it is recharged naturally. We have no role to play. The second, Carbon availability in soil. This needs to be understood fully, since human intervention is required here. - This Carbon is recharged in the soil by Four Means (1) Absorption of CO 2 by moisture present in the soil. (2) Natural manuring by the dead leaves / plants falling on soil. (Tilling will be useful here for the proper assimilation of Carbon in the soil.) (3) Man made manuring by addition of bio-mass – this can be part of the plants grown in the same soil or plants grown exclusively for manure in same soil or some other soil (Here tilling is a must). (4) Addition of Chemical compounds called Fertilizers containing Carbon. The most common compound is Urea. This contains Nitrogen, Hydrogen and Oxygen apart from Carbon. All three are useful. No harmful elements are present. These are not heavy elements like Mercury, Lead, Arsenic, Chromium, etc. - Next is Soil Organic Carbon (SOC) required for the growth of Micro Organisms. SOC is different from Carbon present as Inorganic Compounds (Eg-Calcium Carbonate). The
Carbon present in these inorganic compounds cannot participate in any biological activity. Also, the Carbon as SOC has to be preferably in the form of Bio-Mass. Carbon in the form of simple chemical compounds like Urea are not effective here.Nitrogen (N) - Nitrogen is present in two forms in Plants. 1) As an important element in the Chlorophyll molecule which are present mostly in leaves and green parts of plants. This Chlorophyll molecule only absorbs the sunlight and facilitates the conversion of CO 2 (derived from) Air and H 2 O (derived from soil) into cellulose. This Nitrogen is liberated back to the air as soon as the leaves die or the plants themselves die. That is this Nitrogen is not present in the dry Bio-Mass. 2) As an element in Protein Molecules. This Protein can be a part of the useful product of the plants (like Cereals, Seeds) or can be a part of plant which is not useful to human beings (like nodules in roots). This Nitrogen is fixed and is available even after the Plants die. - Nitrogen is derived by the plants in 2 ways. 1) By the presence of Nitric Acid naturally available in the soil. This Nitric Acid is produced by the absorption of NO 2 present in air by soil moisture (Tilling will be useful). This NO 2 in turn is produced by the Chemical reaction taking place between Nitrogen and Oxygen present in the Air when lightning generates high temperatures in Air. 2) By the addition of Chemical compounds in the form of Fertilizers. The most common fertilizers which carry Nitrogen are Urea and Complex Fertilizers (NPK).Phosphorous (P) & Potassium (K) - These two are part of any plant stem like bones in human beings and animals. They are also present in the products of the plants. These are absorbed in ionic form by the plants. Hence they need to be dissolved in water. - P & K are naturally available in the soil and their percentage varies from soil to soil. - Depending upon the type of plant grown, the extent of removal of these elements from the soil varies. - Even if the entire plant parts are recycled back as manure (which is not taking place anyway), the part of P & K that are going as plant products, (as seeds, fruits, etc) which
enter human/animal bodies to produce bones, are not put back into the soil from where they are taken. Hence, we have to intervene and replace at least that much of P & K. - The replacement has to be by Manuring, Ash addition or chemical fertilizer addition. There are no natural means, as they are not available in air or water.Hydrogen (H) & Oxygen (O) - These two elements are present in every constituent part of the plant – Cellulose, Lignin, Chlorophyll, Protein, Oil, Pulp, etc. - These are derived from Air, Water, Oxygen dissolved in water and Oxygen & Hydrogen present in Organic Chemical compounds which are present in soil. - These Chemical compounds can be from manure or Chemical compounds added by man i.e Fertilizers.Magnesium (Mg) - Magnesium is an essential element for plant growth. Magnesium is the nuclei of Chlorophyll ( like Iron in Hemoglobin present in our blood) - Magnesium is taken from the soil by the plants in ionic form. Hence it has to be dissolved in water. - As long as all the leaves and stems are put back into the soil, majority of the Magnesium will get back into soil and we need not add any Magnesium. - Obviously all leaves and stem do not get recycled. - Hence we have to replace that much of Magnesium. - Magnesium addition has to be either as manure or as some Chemical compound.Sulphur (S) - Sulfur is a component of numerous protein enzymes that regulate photosynthesis and nitrogen fixation. - Plants take Sulfur in the form of Sulphate ion. - It is obtained partly by acid rain and the balance by human intervention in the form of fertilizer or manure addition.
Micronutrients: - Apart from the above elements, there are several other nutrients essential to plant growth and health. These are only needed in very small quantities and hence are called Micronutrients. Each has its own role. - Boron is believed to be involved in carbohydrate transport in plants and it also assists in metabolic regulation. - Chlorine is essential for osmosis and ionic balance; it also plays a role in Photosynthesis. - Cobalt is an important catalyst in Nitrogen fixation. - Copper is a component of some enzymes and Vitamin A. - Iron is essential for Chlorophyll synthesis. - Manganese activates some important enzymes involved in Chlorophyll formation. - Molybdenum is used by plants to reduce nitrates into usable forms. Some plants use it for Nitrogen fixation. - Zinc participates in Chlorophyll formation and also activates many enzymes. - Thus, it is important to note that these Micronutrients are essential for plant growth and hence their product yield. - In general, farmers apply Micronutrients only when crops show deficiency symptoms, while Micronutrient deficiencies decrease yields even before symptoms appear. Hence care should be taken that these nutrients are added to the soil before the crops are seeded unlike NPK Fertilizers. - As none of the above mentioned elements are available in Air or Water and we cannot be sure of their presence in manure to the required level, these Micronutrients have to be necessarily added as chemical compounds only.From the above discussions, we can understand the following:a) Carbon constitutes the major weight of the plant. Though part of the Carbon is obtained from Air(as CO 2 ), almost an equal amount is required to be obtained from soil as dissolved organic acid. Also,Carbon needs to be present in the soil as Bio-Mass as substrate for the micro organisms to grow andsustain the biological activity.We have to replace Carbon at the same rate as the plants remove it from the soil. Understandably therate of removal is going to be proportional to the number of Crops per year and the yield of Crops. If, we
have 3 Crops per year, then the rate of removal will be that much higher. Similarly if Paddy yield is high at6 Tonnes per hectare due to hybrid varieties like Ponni, then there will be that much Carbon removal. Thesame logic is applicable for other elements also.What is the level of Carbon recycle? Since it is difficult to answer this question, let us see how much is notrecycled. The balance is what is recycled. 1. About 13 Lakh tonnes of garbage is generated every day in the Towns and Cities of India. About 40% of this is organic matter which is obtained from soil – It can be Food grains, Banana leaves, fruit skins, Animals, Bamboo, coconuts, Milk, Meat, etc - it is nothing but anything grown in the soil. So, that much Carbon is not going back to soil. As the population increases, the fuel requirement increases. More and more trees grown in the soil are cut and burnt for fuel. That much Carbon is not recycled. A substantial part of the organic matter ( Straws of Rice / Wheat / Sorghum / Millet, Sugarcane leaves, etc) is consumed by animals. Major part of the Carbon present in this organic matter reaches the atmosphere as CO2 and Methane. The remaining part is present in cow dung. At least if all this cow dung reach the fields it is very effective. Unfortunately with rising demand for cooking fuel, this also does not happen. Now the latest trend is Bio-Mass based Power plants! The Agricultural products like Rice Straw, Wheat Straw, Rice husk, Wood Waste, Cashew nut Shells, Groundnut Shells – whatever we can see as burning material – are used in boilers to generate electricity. Where are the Bio-Mass left out for recycling back to the soil? The worst part is that the Ministry of Non-Conventional Energy Sources (MNES) encourages such burning by giving higher price for the electricity generated in Bio-Mass based power plants compared to Wind Mills. What a great wisdom! In similar lines, the MNES is encouraging the Power Plants which use Municipal Solid Waste (MSW). On the one hand the MSW Act 2003 stipulates that these MSW shall be segregated at source as Bio-Degradable and Non – Biodegradable, and the Bio – Degradable substances shall be composted and returned as manure to the soil. On the other hand the MNES discourages Source Segregation, since anyway it is going to be burnt, why we need to emphasize on Source Segregation. If I add one plastic in my garbage, heaven is not going to fall! The result is the old story of the King asking for Milk from everyone in a common vessel and getting completely water
only! Likewise, all plastics and hazardous waste will continue to burn like ever before till we realize that the Dioxin level increases to such high levels that the cancer in Cities and Suburbs increases substantially. 2. We are not putting back the plant products (Grains, Fruits, Oil, etc). About 250 Million Tonnes of Grains, 50 Million Tonnes of Pulses, Oilseeds, etc are produced every year in India. That much of carbon present in these products are not recycled back to the soil. . 3. Part of the Soil Organic Carbon is continuously getting oxidized by the presence of Air and only part of it enters the plant. The remaining enters Atmosphere. 4. Year after year we are adding irrigation and the number of crops per year keeps increasing from one to two, and two to three. Naturally there is additional depletion in the transition from one crop to two crops and two crops to three crops. 5. Similarly, as the yield level of crops increases with the introduction of hybrid varieties, the rate of Carbon depletion also increases to that extent. We cannot avoid introduction of hybrid varieties. Today almost all crops that we plant are hybrid. The Ponni rice which we all enjoy today is a hybrid. It matures in 120 days as against 180 days of the olden day rice variety like “ Sivapparisi”, “Nettai Nell”. The Wheat, Brinjal, Snake Guard, Coconut, Groundnut, Sugarcane - almost every item that we use today is a hybrid. What is wrong about all these? How many have died of Cancer by eating these items? The average life expectancy has actually increased substantially in the past 50 years. So, we have to accept hybrids as the right solution to the growing needs of our ever increasing population. So do GM crops, as long as they are proved to be harmless. Bio-diversity issue of GM crops is something fundamental to the very existence and exploitation of the Planet by the human beings. For that, we can not find fault with GM crops alone. Which means, the Carbon present in all the above mentioned items are not recycled back to the soil? Then how will the soil get back the Carbon removed by the plants? As explained above, the recycling of even 100% of Plant residues does not put back all the Carbon taken by the plants and that is lost by the soil.Hence atleast that much Carbon which is not recycled needs to be replenished in some form or the other.Obviously, Fertilizer is inevitable.
b) Nitrogen taken by the plants is almost lost completely as the plants die - major part, which is in theleaves escapes to the atmosphere. Part quantity present in plant products is consumed by Man / Animal(and only a fraction of it is recycled back to soil). The part quantity present in the root is also not recycledcompletely.Hence we need to intervene and replace at least that much of Nitrogen that is not put back into the soilbetween each crop.Nitrogen addition can be by aeration of soil and addition of Fertilizers. Nitrogen addition can be by Bio –Fertilizers also.c) Phosphorous and Potassium need to be replenished to the extent that they are consumed by Man /Animal in the form of Plant Products (Rice, Wheat, Nuts, Oil Seeds, etc).P&K addition can only be done by Chemical Fertilizers.d) Hydrogen and Oxygen need to be replenished to the extent of diversion of Organic manure whichoriginally provided part of the Oxygen and Hydrogen required by the earlier crops.These two elements can be provided by Chemical Fertilizer only.e) Majority of Magnesium remains in the dead leaves and some quantity remains in other parts of thePlants. Hence, Mg needs to be replenished in the soil to the extent that the leaves and other parts ofplants which are not put back into the soil.Magnesium addition can be done by chemical addition only.f) As for the Micro Nutrients, majority go into the plant products (Grains, Seeds, Fruits, etc) and some areretained in the roots. Hence most of the Micro Nutrients do not get recycled back to the soil.Hence they need to be added to the soil between each crop cycle.The only means of addition of them is by chemical addition.Now, from the above analysis, it is clear that most of the elements required for the plants need to beadded between any two crops, even if we are aiming for the same level of yield per crop, and even if theentire bio-mass produced is put back into the soil.
Since, we are increasing the yield per crop every year with hybrid varieties and also increasing the numberof crops per year, we have to necessarily add these elements.Hence, the much hyped only Organic farming is a misguided adventure!Please note, no one is against recycling of the Organic matter as manure. What we should understand isthat major part of the Organic matter is not recycled back as manure and what is more, even if 100%Organic matter is recycled as manure, still we need to supplement it with Chemical Fertilizers. Secondly,the Fertilizer addition is in no way harmful and inferior to manure, excepting that the Carbon as ChemicalFertilizers will not be useful for the growth of Micro Organisms and definitely we need manure, atleast forthat purpose. If, we can add more manure, then to that extent we can reduce Fertilizer. The Vice versa ismostly true. That is all!Let us analyze another misconception going around the so called “natural farming technique” – That isTilling of land is not required! Their argument is based on two factors:1. Tilling destroys the Microorganisms naturally present in the soil.2. They destroy the Earthworms that grow well if the soil is left undisturbed.What they fail to understand is that Microorganisms and Earthworm can only provide only Nitrogen andOxygen (and that too not enough if we need 3 crops per year) and all other elements need to be addedexternally as chemicals. This chemical addition necessitates tilling, as these elements have to reach theroots for the plants to absorb.We have to add here a few lines about the misconception on the Green Revolution in Punjab. We oftencome across statements like, “Green Revolution with the introduction of Hybrid varieties and chemicalfertilizers has spoiled the soil in Punjab. Hence there is plataeuing of the growth in yield, and we are notable to increase the yield any further, or there is declining trend in some cases.” - See the absurdity of this argument! Before the Green Revolution in 1965 – 66, the yield of Wheat was 1104 kg/hectare and it increased steadily to 2238 kg/hectare in 1970 – 71 and now in 2004 – 05 it is 4221 kg/hectare. This increase in yield is in response to introduction of Hybrid varieties, Fertilizer addition and effective pest control. In recent years the yield is stable. It is common sense that the yield cannot continue to improve indefinitely. There has to be some limit for a given agro climatic conditions. Obviously that limit has been
reached in Punjab. Probably by changing the seeds, we can further improve the productivity. - If there is decline in some areas from the peak yield, then there could be several factors, and one of them could be insufficient Bio-Mass recycle leading to lesser biological activity, as discussed earlier. There could be no scientific reason for reduction in yield due to fertilizer addition.Also, there are some misconceptions about use of pesticides.Why we are using pesticides? There is crop damage beyond some level called “economic threshold”.Hence we are using pesticides. If the pests develop immunity for a particular pesticide after repeateduse, then we have to introduce alternate pesticide. It is as simple as it is! What is wrong about it? If, wecan find natural pesticides which can replace the chemical pesticides, use them in preference to syntheticpesticides. There is no second opinion about it. Earlier, we were using natural pesticides like Neem. Atsome stage, they were not effective. Hence, we introduced chemical pesticides. Simply arguing againstuse of pesticides is half backed wisdom.Another argument is between Chemical pesticides and Bio-pesticides. It is known that all the bio-pesticides are pest specific. Hence, we can use those bio-pesticides if we are sure that only that pest ispresent in the plant. Otherwise we have to use broad spectrum pesticides which are available aschemical pesticides only.What is important is that excessive pesticides are harmful for both plants and human beings. Hence, wehave to be careful in the quantity used and as far as possible minimize the possibility of the residualpesticides getting into the food chain. The consumers need to be cautious while eating anythinguncooked. *******