Sustainable Agriculture

Sustainable agriculture refers to the ability of a farm to produce food perpetually. Two key issues are physical (the long-term effects of various practices on soil properties and processes essential for crop productivity) and socio-economic (the long-term ability of farmers to obtain inputs and manage resources such as labor). While air and sunlight are generally available in most geographic locations, crops also depend on soil nutrients and the availability of water. When farmers grow and harvest crops, they remove some of these nutrients from the soil. Without replenishment, the land would suffer from nutrient depletion and be unusable for further farming. Sustainable agriculture depends on replenishing the soil while minimizing the use of non-renewable resources, such as natural gas (used in converting atmospheric nitrogen into synthetic fertilizer), or mineral ores (e.g., phosphate). Possible sources of nitrogen that would, in principle, be available indefinitely, include: 1) recycling crop waste and livestock or human manure, 2) growing legume crops and forages such as, peanuts, or alfalfa that form symbioses with nitrogen-fixing bacteria called rhizobia, 3) adapting the current industrial nitrogen fixation process to use hydrogen made by electrolysis (perhaps using electricity from solar cells or windmills) instead of natural gas or 4) genetically engineering (non-legume) crops to form nitrogen-fixing symbioses or fix nitrogen without microbial symbionts. The last option was proposed in the 1970s, but would be well beyond the capability of current (2006) technology, even if various concerns about biotechnology were addressed. Sustainable options for replacing other nutrient inputs (phosphorus, potassium, etc.) are more limited. Green Revolution The term is used to describe the transformation of agriculture in many developing nations that led to significant increases in agricultural production between the 1940s and 1960s. The world's worst recorded food disaster occurred in 1943 in British-ruled India. Known as the Bengal Famine, an estimated 4 million people died of hunger that year in eastern India . Initially, this catastrophe was attributed to an acute shortfall in food production in the area. However, Indian economist Amartya Sen has established that while food shortage was a contributor to the problem, a more potent factor was the result of hysteria related to World War II, which made food supply a low priority for the British rulers.

There were three basic elements in the method of the Green Revolution Continuing expansion of farming areas Double-cropping in the existing farmland Using seeds with improved genetics. The area of land under cultivation was being increased from 1947 itself. But this was not enough to meet the rising demand. Though other methods were required, the expansion of cultivable land also had to continue. So, the Green Revolution continued with this quantitative expansion of farmlands. Double cropping was a primary feature of the Green Revolution. Instead of one crop season per year, the decision was made to have two crop seasons per year. The one-season-per-year practice was based on the fact that there is only one rainy season annually. Water for the second phase now came from huge irrigation projects. Dams were built and other simple irrigation techniques were also adopted. Using seeds with superior genetics was the scientific aspect of the Green Revolution. The Indian Council for Agricultural Research (which was established by the British in 1929) was reorganized in 1965 and then again in 1973. It developed new strains of high yield variety seeds, mainly wheat and rice and also millet and corn. The Green Revolution was a technology package comprising material components of improved high yielding varieties of two staple cereals (rice and wheat), irrigation or controlled water supply and improved moisture utilization, fertilizers, and pesticides, and associated management sk Shortcomings In spite of this, India's agricultural output sometimes falls short of demand even today. India has failed to extend the concept of high yield value seeds to all crops or all regions. In terms of crops, it remains largely confined to foodgrains only, not to all kinds of agricultural produce. The Green Revolution has created some problems mainly to adverse impacts on the environment. The increasing use of agrochemical-based pest and weed control in some crops has affected the surrounding environment as well as human health. Increase in the area under irrigation has led to rise in the salinity of the land. Although high

yielding varieties had their plus points, it has led to significant genetic erosion. Since the beginning of agriculture, people have been working to improving seed quality and variety. But the term ‘Green Revolution’ was coined in the 1960s after improved varieties of wheat dramatically increased yields in test plots in northwest Mexico. The reason why these ‘modern varieties’ produced more than traditional varieties was that they were more responsive to controlled irrigation and to petrochemical fertilizers. With a big boost from the international agricultural research centres created by the Rockefeller and Ford Foundations, the ‘miracle’ seeds quickly spread to Asia, and soon new strains of rice and corn were developed as well. By the 1970s the new seeds, accompanied by chemical fertilizers, pesticides, and, for the most part, irrigation, had replaced the traditional farming practices of millions of farmers in developing countries. By the 1990s, almost 75% of the area under rice cultivation in Aisa was growing these new varieties. The same was true for almost half of the wheat planted in Africa and more than half of that in Latin America and Asia, and more than 50% of the world's corn as well. Overall, a very large percentage of farmers in the developing world were using Green Revolution seeds, with the greatest use found in Asia, followed by Latin America. Importance of Soil Soils are one of the most critical natural resources. Vital, healthy soils are necessary to support plant growth and agriculture; without the oxygen and food supplied by plants and crops, life on Earth would not be possible, so the quality of soil ecosystems is a matter of considerable importance. Soils are dynamic ecosystems composed of a combination of minerals, organic matter, and living organisms. The variety of soil types is the result of the diversity of minerals and organisms that compose them. Soils consist of four main mineral types: sand, silt, clay, and loam. Sandy soils have a coarse texture, clay soils have a sticky texture, and silt particles, which are smaller than sand particles, but larger than clay, give soils a silky, powdery texture. Soils in which all three minerals contribute equally to their texture are loam soils, which are the best for agriculture. Mineral and organic particles make up about 50 percent of soil's volume; pores containing air and water make up most of the remaining volume.

Soil quality can be distinguished by color, which is determined by the availability of oxygen and the presence of iron. Red and yellow soils indicate that the soils are well aerated, that is, they are porous and have a substantial amount of oxygen. Poorly aerated soils are gray or olive. Oxygen is required for plant respiration so well aerated soils are most suitable for plant growth. In addition to mineral and organic matter composition, quality of soils is determined by its texture, porosity, ability to retain water, and depth. The quality of soils determines how productive agricultural lands are. Soils also play an important part in recycling carbon; 85 percent of carbon in the atmosphere comes from biological reactions in the soil. As plants and animals decompose, they release carbon dioxide into the atmosphere. Some of the carbon, in the form of plant residues and animal remains, becomes part of the organic material, or humus, in the soil. It is estimated that there is twice as much carbon in soils as in the atmosphere, and three times as much carbon as is stored in all the Earth's vegetation. Irrigation Irrigation is the replacement or supplementation of rainfall with water from another source in order to grow crops or plants. In contrast, agriculture that relies only on direct rainfall is sometimes referred to as dryland farming. Types of irrigation Overhead (sprinkler) irrigation Overhead irrigation of blueberries in Plainville, New York.

Spray Head

In overhead or sprinkler irrigation, water is piped to one or more central locations within the field and distributed by overhead high-pressure sprinklers or guns or by lower-pressure sprays. A system utilizing sprinklers, sprays, or guns mounted overhead on permanently installed risers is often referred to as a solid-set irrigation system. This type of system is commonly used in lawns, golf courses, cemeteries, parks, and other turf areas. Sprinklers that spray in a fixed pattern are generally called sprays or spray heads. Center pivot irrigation

The hub of a center-pivot irrigation system. Center pivot irrigation is a form of overhead irrigation consisting of several segments of pipe (usually galvanized steel or aluminum) joined together and supported by trusses, mounted on wheeled towers with sprinklers positioned along its length. The system moves in a circular pattern and is fed with water from the pivot point at the center of the arc.

Drip, or trickle irrigation Water is delivered at or near the root zone of plants, drop by drop. This type of system can be the most water-efficient method of irrigation, if managed properly, since evaporation and runoff are minimized.

Sub-irrigation Sub-irrigation also sometimes called seepage irrigation has been used for many years in field crops in areas with high water tables. It is a method of artificially raising the water table to allow the soil to be moistened from below the plants' root zone. Manure is organic matter used as fertilizer in agriculture. Manures contribute to the fertility of the soil by adding organic matter and nutrients, such as nitrogen that is trapped by bacteria in the soil. Higher organisms then feed on the fungi and bacteria in a chain of life that comprises the soil food web. Compost is distinguished from manure in that it is the decomposed remnants of organic materials (which may, nevertheless, include manure). Uses Manure has been used for centuries as a fertilizer for farming, as it is rich in nitrogen and other nutrients which facilitate the growth of plants. Liquid manure from pig/hog operations is usually knifed (injected) directly into the soil to reduce the unpleasant odors. Manure from hogs and cattle is spread on fields using a Manure spreader. Due to the relatively lower level of proteins in grasses, which herbivores eat, cattle manure has a milder smell than the dung of carnivores — for example, elephant dung is practically odorless. However, due to the quantity of manure applied to fields, odor can be a problem in some agricultural regions. Poultry droppings are harmful to plants when fresh but after a period of composting are valuable fertilizers. The dried manure of animals has been used as fuel throughout history. Dried manure (usually known as dung) of cow was, and still is, an important fuel source in countries such as India, while camel dung may be used in treeless regions such as deserts. On the Oregon Trail, pioneering families collected large quantities of "buffalo chips" in lieu of scarce firewood. It has been used for many purposes, in cooking fires and to combat the cold desert nights. Another use of manure is to make paper, this has been done with dung from elephants where it is a small industry in Africa and Asia, and also horses, llamas, and kangaroos. Other than the llama, these animals are not ruminants and thus tend to pass plant fibres undigested in their dung.

For the rest the info is not enough or too general. Is safer to do from textbook. Crop Protection, agrochemicals etc.