Table of Contents
- Agriculture is a broad term encompassing all aspects of crop production (food and fibre), livestock farming, fisheries, forestry etc.
- Food and fibre productivity has increased by using new technologies, mechanization, increased use of fertilizers and pesticides and expansion of irrigation facilities.
- These changes reduced the labour demand to produce the majority of the food and fibre.
- Although these changes have had the positive effect, they also caused some serious environmental and social problems such as erosion of top soil, depletion and pollution of groundwater and other water resources, unemployment of farm laborers due to their replacement by farm machinery.
- In view of the growing negative consequences of modern agriculture there is growing demand to promote “sustainable agriculture”.
- Sustainable agriculture is the production of food, fiber, plant or animal products using farming techniques that protect the environment, public health, human and animal welfare.
- Sustainable agriculture incorporates many environmentally safe agricultural practices and offers innovative and economically viable opportunities for farmers, laborers, consumers, policymakers and many others in the entire food system.
- Sustainable farming systems are those that are least toxic and least energy intensive and yet maintain productivity and profitability. E.g. Organic farming.
- Thus, sustainable agriculture is one that,
- supports profitable production;
- protects environmental quality;
- uses natural resources efficiently;
- provides consumers with affordable, high-quality products;
- decreases dependency on non-renewable resources;
- enhances the quality of life for farmers and rural communities; and
- will last for generations to come.
- At the planning level one must take into account the local geography (topography), soil condition and nature, local climate, pests, local inputs and the farmer’s goals.
- The grower (farmer) must then select appropriate practices.
- Several methods adopted in sustainable agriculture are:
- cultivation practices to increase biological and economic stability.
- selection of improved varieties to suit the need.
- soil management by proper method of tillage.
- In mixed cropping or diverse cropping two or more crops are grown all at the same time in a field.
- If by chance one crop fails, the others crops cover the risk of total crop failure.
- Usually a long duration crop is grown with a short duration one so that both get sufficient nutrition at the time of maturity.
- Generally a leguminous crop is grown along with the main crop.
- Legumes helps to increase soil fertility by fixing atmospheric nitrogen. This saves the cost of chemical fertilizers.
- The various plans followed in diverse or mixed cropping practices are:
- polyvarietal cultivation where several genetic varieties of the same crop are planted.
- intercropping where two or more different crops are grown at the same time on a plot like carbohydrate rich cereal that uses soil nitrogen and nitrogen fixing legume that puts back the nitrogen in the soil.
- polyculture, in which different plants maturing at various times are planted together.
- This practice has many advantages because fertilizer and water requirement of plants are different so there is less need of these inputs.
- Pests are controlled naturally because their natural predators find multiple habitats to survive.
- It has been found that this practice produces much higher yield per hectare compared to monoculture.
- It is practice of growing different crops in regular succession in the same field.
- This practice controls insects and diseases, increases soil fertility and decreases soil erosion.
- Generally soil cannot sustain continuous cropping with high yielding single crop because certain nutrients required by the crop get exhausted totally while others remain unutilized leading to serious nutrients imbalance in soil and encouraging certain diseases and pests.
- Sowing a leguminous crops (e.g. green gram) as a rotational crop is very useful because legumes enhance nitrogen level in the soil, reduces the need for chemical nitrogen fertilizer thereby saving the soil from the harmful effects of using high yielding varieties along with the application of large amount of fertilizer, pesticides and water.
- It is possible to grow two or sometimes three different crops in succession on the same land within a year is known as multiple cropping. This practice can go on for some time but the land cannot maintain high yield in the long run.
- Crop rotation takes into amount the following factors:
- Leguminous crop should be grown after non-leguminous crop.
- Crops require less water (irrigation) should be grown after one – that requires more water.
- Crops requiring less manure should be sown after one that requires more manure.
- Important crop patterns of crop rotation
- Green gram – Wheat – Moong
- Ground nut – Wheat – Moong
- Arhar – Sugarcane – Wheat – Moong
- Paddy – Wheat – Moong
- Optimum diversity may be obtained by integrating both crops and livestock in the same farming operation.
Mixed crop along with livestock operations have several advantages.
- Growing crops only on more level land and pastures or forages on steeper slopes will reduce soil erosion.
- Pasture and leguminous forage crops in rotation enhance soil quality and reduce erosion; livestock manure, in turn, contributes to soil fertility.
- Livestock can buffer the negative impacts of low rainfall periods by consuming crop residue which in “plant only” systems would have been considered crop failure.
- Feeding and marketing are flexible in animal production systems. This can help cushion farmers against price fluctuations and, make more efficient use of farm labour.
|Strip Farming: This method is another method of soil erosion. This involves planting the main crops in widely spaced rows and filling in the spaces with another crop to ensure complete ground cover. The ground is completely covered so it retards water flow which thus soaks down into the soil, consequently reducing erosion problems.|
- A healthy soil is a key component of sustainable agriculture. That is healthy soil along with water and nutrients produces healthy crops that are less susceptible to pests and diseases.
- Accordingly, soil must be protected and nurtured to ensure long term productivity and stability.
- Methods of protection include using cover crops, compost, reducing tillage, conserving soil moisture by dead mulches, this increases water hold capacity of the soil.
- There are sixteen nutrients which are essential for plants.
- Air supplies carbon and oxygen, hydrogen comes from water, and soil supplies the other thirteen nutrients to plants.
- Amongst these thirteen nutrients, six are required in large quantities and are therefore called macronutrients.
- The other seven nutrients are used by plants in small quantities and are therefore called micronutrients
- Deficiency of these nutrients affects physiological processes in plants including reproduction, growth and susceptibility to diseases.
- Based on the relative abundance in plants, viz., Nitrogen (N); Phosphorous (P), Potassium (K), Sulfur (S), Calcium (Ca) and Magnesium (Mg)
- Their concentration is very small. They are also referred to as minor elements.
- Iron (Fe); Zinc (Zn); Manganese (Mg), Copper (Cu), Boron (B), Chlorine (Cl) and Molybdenum (Mo).
- In some plants, other than the above, Sodium (Na), Cobalt (Co), Vanadium (Va), Nickel (Ni) and Silicon (Si) are considered as essential micronutrients
- N is an essential constituent of proteins and is present in many other compounds of great physiological importance in plant metabolism
- N is an integral part of chlorophyll, which is primary observer of light energy needed for photosynthesis.
- N also imparts vigorous vegetative growth and dark green colour to plants.
- Phosphorus (P) is an essential part of the enzymes which help the crop to fix light energy.
- It forms an integral part of nucleic acids, the carriers of genetic information, and is important in stimulating root growth
- Potassium (K) is involved in processes which ensure carbon assimilation and the transportation throughout the plant for growth and the storage of sugars and proteins.
- The potassium ion is also important for water regulation and uptake.
- Furthermore, the presence of potassium in sufficient amounts ensures resistance to frost, drought and certain diseases
- Magnesium occurs in chlorophyll and is also an activator of enzymes,
- Sulphur forms part of two essential amino acids which are among the many building blocks of protein. It is also found in vitamin B1 and in several important enzymes.
- Calcium is required for plant growth, cell division and enlargement. The growth of root and shoot tips and storage organs is also affected by calcium as it is a component of cell membranes. Calcium is also vital for pollen growth and to prevent leaf fall.
- For a sustainable agriculture system, it is essential to use renewable inputs (fertilizer, pesticides, water etc.) which can benefit the plant and cause no or minimal damage to the environment.
- One of the energy efficient and pollution free method is to exploit the ability of certain microorganisms like bacteria, algae and fungi to fix atmospheric nitrogen, solubilize phosphorus, decompose organic material or oxidize sulphur in the soil.
- When they are applied in the soil, they enhance growth and yield of crops, improve soil fertility and reduce pollution. They are known as “bio fertilizers”.
- Thus bio-fertilizers are living or biologically active products or microbial inoculants of bacteria, algae and fungi (separately or in combination) which are able to enrich the soil with nitrogen, phosphorus, organic matter etc.
- Following are some of the important types of bio fertilizers which can be considered for agro based industries.
- Rhizobium is a symbiotic bacteria forming root nodules in legume plants. These nodules act as miniature nitrogen production factories in the fields.
- The nodule bacteria fix more nitrogen (N2) than needed by legume plant and the bacteria. The surplus fixed nitrogen is then secreted and fertilizes the soil.
- Rhizobium is more efficient than-free living nitrogen-fixing bacteria.
- Azotobacter are aerobic free living nitrogen fixers.
- They grow in the rhizosphere (around the roots) and fix atmospheric nitrogen nonsymbiotically and make it available to the particular cereals.
- These bacteria produce growth promoting hormones which helps in enhancing growth and yield of the plant.
- These are aerobic free living nitrogen fixers which live in associative symbiosis.
- In this type of association bacteria live on the root surface of the host plant and do not form any nodule with roots of grasses.
- It increases crop yield and its inoculation benefits crop. They also benefit the host plants by supplying growth hormones and vitamins.
- These bacteria are commonly used for the preparation of commercial inoculants (vaccines, culture medium).
- Blue green algae (BGA or cyanobacteria) like Nostoc and Anabaena are free living photosynthetic organisms also capable of fixing atmospheric nitrogen.
- In the flooded rice fields blue green algae serves as a nitrogen biofertiliser.
Consider the following organisms
Which of the above is/are used as biofertilizer/biofertilizers
- 1 and 2
- 2 only
- 2 and 3
- 3 only
Answer: b) 2 only [Not sure]
- Azolla is a water fern inside which grows the nitrogen fixing blue green algae Anabaena.
- It contains 2-3% nitrogen when wet and also produces organic matter in the soil.
- The Azolla-Anabaena combination type biofertiliser is used all over the world. This can be grown in cooler regions.
- But there is a need to develop a strain that can tolerant to high temperature, salinity and resistant to pests and diseases.
- Production technology is very easy and can be adopted by rice farmers.
- The only constraint in Azolla is that it is an aquatic plant and water becomes limiting factor in growing it particularly in summer.
- Phosphorus is an important element required for plant growth. This element is also needed for nodulation by rhizobium.
- Some microorganisms are capable of solubilizing immobilized phosphorus making it available to plants for absorption.
- Mycorrhizal fungi acts as biofertiliser and are known to occur naturally on roots of forest trees and crop plants.
- Mycorrhizal fungi resist disease in plants. The plants also show drought and salinity resistance. Plants can tolerate adverse soil, pH, high temperature and heavy metal toxicity.
- In soils low in available nutrients there is an increased absorption of nutrients by plants infected with Mycorrhiza.
- The fungus has the ability to dissolve and absorb phosphorus that plant roots cannot readily absorb.
- A wise way will be to develop an integrated nutrient supply system involving the combination of chemical fertilizers and biofertilisers.
Mycorrhizal biotechnology has been used in rehabilitating degraded sites because mycorrhiza enables the plants to
- resist drought and increase absorptive area
- tolerate extremes of pH
- Resist disease infestation
Select the correct answer using the codes given below:
- 1 only
- 2 and 3 only
- 1 and 3 only
- 1, 2 and 3
Answer: d) all
- Compost Tea is a Liquid fertilizer for flowers, vegetables and houseplants.
- Compost tea is an aerobic (in the presence of oxygen) water solution that has extracted the microbe population from compost (dead and decaying matter) along with the nutrients.
- In simple terms, it is a concentrated liquid created by a process to increase the numbers of beneficial organisms as an organic approach to plant/soil care.
- Air is sent through the water to keep the water oxygenated, as this favors the beneficial bacteria and fungi over the pathogens.
- At the end of the brewing cycle, what you have is a concentrated liquid full of billions of microorganisms (bacteria, fungi, protozoa, nematodes) that can then be sprayed directly onto the leaf surface.
- The liquid fertilizer occupies the infection sites on the leaf surface and is held there by simple sugars that the plant puts out that work as a glue to keep the beneficial microorganisms thriving and protecting the plant.
- Bio char is found in soils around the world as a result of vegetation fires and historic soil management practices.
- Intensive study of bio char-rich dark earths in the Amazon (terra preta), has led to a wider appreciation of bio char’s unique properties as a soil enhancer.
- Bio char is charcoal that is as soil amendment (minor improvement).
- It created using a pyrolysis process (decomposition brought about by high temperatures), heating biomass in a low oxygen environment.
- Once the pyrolysis reaction has begun, it is self-sustaining, requiring no outside energy input.
- Byproducts of the process include syngas (H2 + CO), minor quantities of methane (CH4) (greenhouse gas), organic acids and excess heat.
- Once it is produced, bio char is spread on agricultural fields and incorporated into the top layer of soil.
- The syngas and excess heat can be used directly or employed to produce a variety of biofuels.
Agricultural Benefits of Bio char
- It increases crop yields, sometimes substantially if the soil is in poor condition.
- It helps to prevent fertilizer runoff and leeching, allowing the use of less fertilizers.
- It retains moisture, helping plants through periods of drought more easily.
- Most importantly, it replenishes exhausted or marginal soils with organic carbon
- It fosters the growth of soil microbes essential for nutrient absorption, particularly mycorrhizal fungi.
- Bio char can increase soil fertility of acidic soils (low pH soils)[pH < 7 = Acidic Soils; pH > 7 = Basic Soils] [The most fertile soils are slightly acidic (pH just below 7)]
- Bio-char reduces the acidity of the soil, protects the plants from diseases, promotes growth of friendly microorganisms, and reduces the loss of micro nutrients apart from increasing water retain-ability.
Kollam, Kerala, is famous for fishing and fishery-related activities; as an agricultural sector, it does not evoke any enthusiasm. Why?
- With the prevailing soil and climatic conditions which favors leaching and draining of soil nutrients into the Arabian sea and Ashtamudi Lake, the soil has high acidity making it unfit for cultivation of any kind (Why? Because friendly microorganisms don’t like acidic medium. They like slightly alkaline or basic medium [having a pH greater than 7]).
- Bio char can make a difference to the agriculture of the region.
Other Environmental Benefits
- Most carbon in the soil is lost as greenhouse gas (carbon dioxide, CO2) into the atmosphere if natural ecosystems are converted to agricultural land.
- Soils contain 3.3 times more carbon than the atmosphere.
- This makes soils an important source of greenhouse gases but also a potential sink if right management is applied.
- The use of crop residues for bio-energy production reduces the carbon stocks in cropland.
- Further the dedication of cropland to bio-fuel production increases the area of cultivated land and thus carbon loss from soils and vegetation.
- Bio char remains stable for millennia, providing a simple means to sequester carbon emissions.
- If bio char is returned to agricultural land it can increase the soil’s carbon content permanently and would establish a carbon sink for atmospheric CO2.
- Organic farming is a type of agriculture or farming which avoids the use of synthetic fertilizers, pesticides, growth regulators, and livestock feed additives.
- Organic farming systems rely on crop rotation, crop residues, animal manures, legumes, green manure, off-farm organic wastes and biofertilisers, mechanical cultivation, mineral bearing rocks to maintain soil productivity to supply plant nutrients and biological pest control, controlling weeds, insects and other pests.
- All kinds of agricultural products can be produced organically, including grains, meat, dairy, eggs, fibres such as cotton, jute, flowers etc. Thus organic farming creates a sustainable lifestyle for generations to come.
- Organic farmers build healthy soils by nourishing the microbial inhabitants that release, transform, and transfer nutrients.
- Soil organic matter contributes to good soil structure and water-holding capacity.
- Organic farmers feed soil biota and build soil organic matter with cover crops, compost, and biologically based soil amendments. These produce healthy plants that are better able to resist disease and insect predation.
- Organic farmers’ primary strategy in controlling pests and diseases is prevention through good plant nutrition and management.
- Organic farmers use cover crops and sophisticated crop rotations to change the field ecology, effectively disrupting habitat for weeds, insects, and disease organisms.
- Weeds are controlled through crop rotation, mechanical tillage, and hand-weeding, as well as through cover crops, mulches, flame weeding, and other management methods.
- Organic farmers rely on a diverse population of soil organisms, beneficial insects, and birds to keep pests in check.
- When pest populations get out of balance, growers implement a variety of strategies such as the use of insect predators, mating disruption, traps and barriers.
Some important benefits of organic farming and organic foods
- Organic farming can be learnt easily by any conventional farmer.
- Switching to organic farming, conventional farmer can actually reduce its production cost by over 25% as.
- Eliminates the use of expensive synthetic fertilizers and pesticides, minimizing soil degradation.
- Organic farms can support substantially higher levels of wildlife especially in low lands and where animals can roam in pastures or graze on grassland.
- Entire ecosystems and ground water are improved by simply following organic farming methods.
- When dairies feed their cows organic feed and graze them on organic fields, the cows experience better health, less sickness, diseases and ultimately produce better tasting milk for consumers.
- Organic farming promotes healthy soils rich in micro nutrients and which can be used for decades to grow crops without getting exhausted.
- Consumers purchasing organically grown foods are tastier.
- Organically grown products are free from harmful chemicals, artificial flavors and preservatives that ultimately cost consumers more money than non-organically grown products.
- Vermicomposting is an appropriate technique for efficient recycling of animal wastes, crop residues and agro-industrial wastes.
- The process of conversion of organic materials into manure is chiefly microbiological.
- Earthworms are important for producing vermicompost from organic wastes.
- Vermicompost can be prepared from all sorts of organic residues – animal waste, sericulture residues, dairy and poultry residues, bagasse from sugarcane factories, sorghum straw, rice straw after feeding cattle, dry leaves, groundnut husk and wheat husk, waste vegetables, weeds (particularly Parthenium hysterophorus or Congress weed before flowering) etc..
- In this approach, each crop and its pests are evaluated as parts of an ecological system.
- Then farmers develop a control programme that includes cultivation, biological and chemical methods applied in proper sequence and with the proper timing.
- The aim of IPM is not to eradicate the pest population completely but to keep the crop damage to economically tolerable level.
- Farmers monitor the field and when they find the pest level to be high enough, they first use biological methods and cultivation practices to control and then use small amounts of insecticides mostly insecticides derived from plants as a last resort.
Biological control includes
- Natural predators, parasites and pathogens of the pests are used.
- Pest on cucumber plant called red spider mite is controlled by using a predatory mite that feed on red spider mite.
- Citrus fruits in California heavily damaged by scale insects which were controlled by Australian ladybird which ate away the insects.
- A variety of cultivation practices like crop rotation, polyculture and inter cropping etc. can be used to get rid of the pests.
- Some amounts of insecticides, mostly of plant origin (e.g. Pyrethrum and Rotenone neem product) are applied as a last resort.
- Pest and disease resistant crop plants can be produced by genetic engineering. Example is Bt cotton, insecticidal for bacterial gene (Bacilus thuringinesis) introduced into cotton plant making cotton plant resistant to pest.
- Farmer should have an expert knowledge about each pest.
- It acts more slowly than conventional pesticides.
- Methods developed for a crop in one area might not apply to areas with even slightest different growing conditions.
- Initial cost may be higher but in the long-term cost become very low.