Precision Agriculture: A step towards a more sustainable agriculture
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At first, this blog entry will shortly describe why a more sustainable agriculture is needed; in this context, precision agriculture will be discussed subsequently.
The invention of the plow is generally regarded as a great step toward increasing crop yields. Crop yields can be increased by plowing, as locked-up soil fertility is released and surface litter is thoroughly mixed with the soil, adding organic matter to be decomposed.
By tilling the soil’s surface area is increased and oxygenated. This oxygenation activates the microbial soil life, which in turn commences to decompose and mineralize organic matter (humus). This releases vast amounts of inorganic compounds such as phosphate, nitrogen and potassium. Newly created oxygenated surface structures are successively colonized by bacteria, reinforcing the release of inorganic matter. For the first growing season, this increase of available nutrients results in high yields. However, tilling releases amounts of nutrients that cannot be incorporated and used by plants, and the excess of fertility is washed away. If the soil is tilled for several growing seasons, the humus (which holds on to many of the inorganic compounds) is depleted and the soil life impoverishes (soil habitat is succeedingly disturbed, e.g. burrows of pill-bugs and earthworms). The prevalence of inorganic compounds must then be artificially simulated by application of chemical fertilizers. However, without humus and a balanced and functioning soil fauna (nutrient cycling among fast-living microbes), the surfeit nutrients cannot be kept in the soil and leach out into the groundwater. Plants use often only 10, rarely more than 50 percent of the fertilizer applied.
Many studies demonstrate that plants grown in soil with rich organic matter are more disease- and insect resistant than plants in carbon-depleted soils. Moreover, mild tilling increases the regeneration from the seed bank by exposing buried soils, potentially increasing presence of weeds.
Pesticides are then applied. The environmentally adverse effects of pesticides emerge mainly because 95-98% of them do not reach their target species (as they are sprayed across the entire agricultural field). Furthermore, if occupationally exposed to herbicides (mainly through inhalation of aerosols), many of them are toxic (glyphosate) or carcinogenic (Picloram, dioxins and triazines) to human and animals (e.g. birds).
Organic farming is mainly reliant on production practices that bypass synthetic chemicals (pesticides and fertilizers), such as crop rotation, adjustments to planting and harvesting dates, the use of beneficial organisms, animal manure, mulching with crop residues or cover crops to build humus and providing habitat for carabids and other animals through hedges and thereby increasing species richness.
According to Eurostat data, during the last decade, organic area in the EU improved by about 500 000 hectares per year: up from 5.7 million in 2002, the EU-27 had in 2011 a total area of 9.6 million hectares of cultivated organic farming land. As big as the increase might appear, the whole organic area, however, represents only 5.4% of total utilized agricultural area in Europe. Growing demand for organic certified food might increase in Western Europe with rising environmental awareness, however often conventionally produced food is cheaper and more affordable for the vast majority of people. Additionally, it remains questionable if organic farming can feed an expected population of 9 billion people in 2050, i.e. it remains unfortunately unclear if organic farming can be socially and economically viable.
An economically viable and environmentally sound, sustainable agriculture must therefore be advanced. Precision agriculture provides a method of approaching the realization these two aspects of sustainability: Through the combined use of remote sensing data, GIS and GPS software tools, and on-tractor variable rate technologies, farmers can use precision tools to maximize efficiency, improve profitability by lowering costs and producing higher crop yields, while minimizing environmental impacts.
A field of crops is no longer treated as a homogenous unit. Spatial as well as temporal heterogeneity, i.e. differences in crop yield, terrain features/topography, organic matter content, moisture levels, nitrogen levels, pH, soil electrical conductivity, weed occurrences, pest outbreaks, etc., can be visualized on maps and adequately managed. For instance, several GIS maps may show in which parts of the field the soil is moistest, or eroded over the winter, in combination with remote sensing data, collected 24 hours ago via e.g. Unmanned Aerial Vehicles (UVAs), aircrafts or satellites that show where plants are stressed or thriving (a plant emits more infrared light when under stress as stomata close and the plant transpires less, which can be recorded with NDVI sensors), one can precisely allocate, irrigation, fertilizers and pesticides. Here, the environmental risk is reduced, as e.g. fertilizer may be applied precisely where it matches the crop needs, thereby limiting the leaching of nitrogen. Additionally, data-driven planting devices can determine variable planting rates to accommodate varying conditions across the field, in order to maximize yield. And by the use of vehicle guidance, the amount of overlap, be it in seed placement or fertilizing can be reduced. For instance a 2006 study by the USDA found that guidance systems can reduce fertilizer, spraying and planting overlaps from 61 to 5 cm, which saves about $13,000 in variable costs annually for a farm of 400 hectares, which would return the initial investment of $10,000 to $20,000 cost of an automated, GPS driven planting within two years.
Thus, from an environmental and economic perspective, precision agriculture might be a step towards achieving a more sustainable agriculture that is able to feed the world. Lastly, if this technology were transferred to poorer countries, e.g. to South America, it could reduce the expansion of agriculture and the consequent clearcutting of forests as the cheapest way of increasing profits.