1. Water management ın general
Water management in agriculture is a critical evaluation of the benefits, costs and impacts of the past 50 years of water development, the water management challenges communities face today and the solutions people developed around the world.
Will there be enough water to grow enough food? Yes. If…The question is, is there enough land, water and human capacity to produce food for a growing population over the next 50 years? Or will we run out of water? It is possible to produce the food-but it is probable that today’s food production and environmental trend, if continued, will lead to crises in many parts of the world. Only if we act to improve water use in agriculture, will we meet the fresh water challenges facing humankind over the coming 50 years?
50 years ago the world had fewer than half as many people as it has today. They were not as whealthy. They consumed fewer calories, ate less meat and thus required less water to produce their food. The pressure they inflicted on the environment was lower. They took a third of the water from the rivers that we take now.
Today the competition of scarce water resources in many places is intense. Many river basins do not have enough water to meet all the demands.-or even enough water for their rivers to reach the sea. Further appropriation of water for human use is not possible because the limits have been reached and in many cases breached. Basins are effectively “closed” with no possibility of using more water. The lack of water is thus a constraint to producing food for hundreds of millions of people. Agriculture is central in meeting this challenge because the production of food and other agricultural products takes 70 % of the fresh water withdrawals from rivers and groundwater. Without better water management in agriculture the millennium development goals for poverty, hunger and sustainable environment can not be met. Without further improvements in water productivity of major shifts in production patterns the amount of water consumed by evapotranspiration in agriculture will increase by 70%-90% by 2050. The total amount of water evaporated in crop production would amount to 12.000-13.500 cubic kilometres almost doubling the 7.130 cubic kilometres of today.
In the early years, much effort went into building check dams and bunds to stop the soil erosion in the barren land. The water which improved vastly is once again under the threat of saline contamination of aquifers. Efforts are being made to re-charge and achieve a water balance, through: awareness and outreach programs to neighbouring villages; extensive water harvesting through check dams and bunding; as well as waste water treatment.
Most people are wasteful of water and treat access to plentiful water as a right. They think little about our water consumption and less about reducing our use. Despite recent improvements in awareness of water sustainability, there is still very little recycling of grey water (water used in the home, excluding water used in the toilet, which is black water). But in reality the fresh water resources of Planet Earth are a rare and enormously valuable resource.
Of all the water on earth, 97% is in the oceans, 2% is contained in glaciers and only 1% is on land. Of the 1% on land, 97% is below the surface, as groundwater, and more than half of that is out of reach.
Of the global reserves of fresh water, 0.06% is in soil moisture, 0.3% is in lakes, 0.03% is in rivers and 0.03% is in the atmosphere as water vapour. Only 11.39% of global freshwater is accessible, non-saline water.
Of the liquid fresh water found at the surface, 30% is in lakes in Africa, 25% in lakes in North America, 18% is in Lake Baykal (Russia) and 27% is in smaller lakes and rivers elsewhere in the world. Rivers are really insignificant in global terms. They carry only 1,200 km3 compared with 125,000km3 in fresh water in lakes and inland seas. (-www.tmorganics.com-)
1.2 Irrigated agriculture
In the past half century there have been massive investments in large scale public surface irrigation infrastructure as part of efforts to increase world staple food production and ensure food self-sufficiency. Irrigation water was essential to achieve the gains from high yielding fertilizer-responsive crop varieties.
Especially in recent years, an increasingly common form of irrigation is the drip irrigation system. This is the most suitable system of irrigation systems.
In Drip system, roots of plants are watered drop by drop with the help of pipes laid in the region. Thus, the water passes directly into the soil without any evaporation and with less water the best yield is achieved. Drought and global warming in recent years, has increased the importance of irrigation to be made consciously. (http://tr.wikipedia.org/wiki/Sulama)
Irrigation, encourages development of species and varieties, and provides efficiency. It is also effective in the development of buds, it reduces the loss. However, it has a negative impact during the blooming period, it causes an increase in fruit size. Irrigation techniques, vary both acording to the species and varieties and to the methods of tillage.
In organic agriculture irrigation, water should be applied properly, in a way not to accumulate in the root zone which and will not cause any root decay, additionally, proper planting techniques and irrigation frequency should be applied.
In organic production, keel irrigation techniques can not be used in the agricultural fields. The plant’s water plan is prepared according to the amount of water to be consumed. Water meter placed in the land and water is used as measured according to the schedule of irrigation. Furrow irrigation is allowed in cases of necessity under the supervision of inspection and certification company.
In a heavy clay soil with defective drainage, low permeability rate, drainage system should be used for irrigation.
1.2.1. Water use in organic farms
There is ample anecdotal evidence and some experimental evidence that organic farms use less water than conventional farms. Anecdotal evidence from many growers, especially irrigation users, indicates that organic growers apply water less often than their non-organic neighbours. It is reasonable to assume that this is largely due to increased soil moisture storage in soils well supplied with organic matter, and to common cultural practices on organic farms, such as use of mulch. Mulch may directly limit evaporation from the soil surface and prevents soil from forming a water-resistant crust, but also allows plant roots to more effectively use the top five centimetres of soil, by keeping them cool and protected from bright light. Better water use on organic farms may also be due in part to greater awareness of water management issues by organic farmers, including plant requirements and irrigation programming, and a greater willingness to directly observe soil moisture, or to use remote sensing devices to help manage irrigation.
We may also reasonably speculate that avoidance of very-soluble fertilisers and long-lasting pesticides on organic farms cause organic growers to contribute less to off-farm water quality issues than their conventional neighbours. Again we could assume that significant awareness of environmental impacts, combined with (at least) annual inspection of environmental performance indicators on certified farms will ensure that the most unsustainable practices do not occur on organic farms and that most organic growers are not causing major water quality issues downstream
1.2.2. Water use by plants
Vegetation transpires at least 100 times more water per annum than is present in the plant as biological water. This figure varies greatly with different plant types, according to their specific adaptations for preserving water. For instance, drought-adapted plants have a much greater capacity to close down stomata (pores on the leaf surface) to limit transpiration. Plants are therefore a type of water pump. They move large volumes of water because they use it as a medium to extract dissolved nutrients, and as an evaporative cooling mechanism – a room with plants will always feel cooler. A plant with a large leaf area, such as a mature apple tree, is therefore capable of removing many tonnes of soil water during the growing season.
Plants have many different adaptations to help them obtain, and conserve moisture. A grape vine, for instance, may put down water-seeking roots to a depth of 40metres. Sometimes, there are roots 50 mm across nearly 50 metres below the surface. Presumably they are seeking groundwater at the level of the river or below, still nearly 10 metres lower, but the trees on the surface are less than 15metres tall.
While plants may have deep roots for survival, they will generally prefer to seek water at or near the soil surface, where air and nutrients are readily available. If there is not a continual input of water into soil, plant roots will dry out the soil around their main feeding roots. Some of this water can be replaced by capillary action (water seeping upwards through the soil pores), but there is always a tension between the two forces of gravity (pulling water down) and capillarity (pulling water up).
Irrigation is also an important factor in terms of disease control in organic agriculture. Selection of irrigation system ( mini-sprinkler, drip, furrow), irrigation time and irrigation ranges should provide enough the water needs of the product. Over-irrigation facilitates the development of soil borne pathogenic fungi. Sprinkler irrigation system should not be preferred against many leaf diseases. Because sprinkler irrigation encourages the development of leaf diseases and distribution of the pathogen. Therefore, drip irrigation and irrigation system from the bottom should be preferred.
Drip irrigation: Drip irrigation, also known as trickle irrigation or microirrigation is an irrigation method which minimizes the use of water and fertilizer by allowing water to drip slowly to the roots of plants, either onto the soil surface or directly onto the root zone, through a network of valves, pipes, tubing, and emitters.
Water sprinkler: In sprinkler or overhead irrigation, water is piped to one or more central locations within the field and distributed by overhead high-pressure sprinklers or guns.
Rain gun: Rainguns are similar to water sprinkler, except that they generally operate at very high pressures and flows.
Direct water irrigation: In surface irrigation systems water moves over and across the land by simple gravity flow in order to wet it and to infiltrate into the soil.
Irrigation is giving water required to be met by natural means to the plants in the soil in different ways so that they can continue their growth and vital activity.
Flood irrigation is the oldest and still the most common type of irrigation. Flood irrigation has two advantages. It is easy to manage (low technology) and most of, or the entire root zone, of the plant is watered. However flood irrigation is wasteful of water and is the major cause of environmental damage. The reason for the wastefulness and damage caused by flood irrigation is the same. Unless the irrigation bays are very short and the delivery time for water is also very short (i.e. there is very good pressure) the water at the start of the irrigation bay will have infiltrated below the main root zone of the plant (and therefore be effectively wasted, or unrecoverable by the crop) before water has reached the end of the bay. Flood irrigation can be slightly improved by delivering water in surges, so that the wetting front has time to cause soil to expand and pore spaces seal, thereby minimising soakage at the start of the bay.
Sprinkler systems can be much more efficient, depending on irrigation timing and management. Short irrigation cycles, especially during the hot part of the day, result in 80% of water being lost to evaporation or by blowing away on the wind. It is probable that 40% of all water applied to lawns is lost to evaporation, even accounting for nighttime irrigation. Very long irrigations cause water to soak past the root zone. Remember too, that even after the system is turned off, water will continue to soak through the soil profile.
Drip irrigation is now considered much more efficient than all systems. One significant advantage is restriction of water to weeds in the inter-row area. The main limitation on efficiency of drippers is the narrow zone of distribution of water, which results in plants having very restricted root zones. There may also be increased salinity at the margin of the wetted rim. Drippers are also sometimes mismanaged, by having a long duration of operation and inadequate frequency of irrigation.
As it is known, the most important input for increasing agricultural production is irrigation.
However, the implementation of the various methods of irrigation depends on certain conditions. Traditional surface irrigation methods can be only be applied, if the land has been leveled. In addition, plenty of water and the quality, must be suitable for irrigation.
Is irrigation not used in regions with scarce water or in where the water is saline?
Of course, it is not an obstacle that the water is problematic in these regions, if the climate and the land are suitable for cultivation in high economic value. Plants with high value, provide high income. In order to achieve this, a new irrigation method has been developed that eliminates the problems of the water. The name of this new method is becoming increasingly popular in the world is drip irrigation. Drip irrigation, also known as trickle irrigation or microirrigation is an irrigation method which minimizes the use of water and fertilizer by allowing water to drip slowly to the roots of plants, either onto the soil surface or directly onto the root zone, through a network of valves, pipes, tubing, and emitters. Drip irrigation is actually an expensive irrigation system. However, since it requires less labor and allows automatic watering it is applied for the greenhouses and in planting of high economic value products especially in initial investment stages. The droppers are the heart of the irrigation system. They are made of plastic and mounted on the pipes called lateral pipes with the diameter between 12 and 32 centimeters. The drippers drop the water to the soil in a rate that few liters of water is dropped per hour.
A successful solution to bio-organic agriculture means ensuring optimal plant nutrition while restoring the soil and its micro-organisms to their natural state. With synthetic fertilizer, pesticides and herbicides prohibited, compost and other organic and natural nutrient sources play a key role. Nevertheless, using natural nitrogen sources for fertilization in the irrigation system requires special attention, such as proper filtration and maintenance as well as periodical flushing of the drip system to avoid potential clogging.
a) Dealing with clogging:
One of the major problems affecting the efficiency of organic agriculture irrigation is the creation of bacterial slime and lime scale, which can decrease flow rate and clog the dripper. This problem was resolved by providing suitable disinfestation to enable the free flow of nutrient-enriched water through the pipes.
b) Using compost:
Composting is vital for organic production. It efficiently treats and stabilises fresh organic material, destroys weed seeds and pathogenic microbes, reduces the volume of organic waste and prevents environmental pollution. Adding compost to the soil improves its physical characteristics, aerates heavy and clay soils, improves the water retention capacity of light and sandy soils, stimulates the development of biomass, reduces the carbon/nitrogen ratio and provides the soil with humic elements.
When used in compost preparation, low-volume irrigation technology, either micro-sprinklers or drip-lines, is extremely effective in preventing nutrient leaching and resulting environmental contamination.
c) Advantages related to the use of drip irrigation and organics
• Ensures accurate irrigation and Nutrigation
• Reduces weeds
• Activates compost as the main source of nutrients
• Saves water, reduces runoffs
• Maintains the correct water and air balance in the soil
• Prevents diseases; drip irrigation keeps leaves and fruit dry- Economizes on manpower costs and minimizes hands-on involvement
d) A drip irrigation system consists of 4 parts besides emitters. These are:
1.Control Unit: Consists of the filters in which water and fertilizer are filtered, gauges (manometer) which control pressure, valves, and fertilization tank. There are three filters in the control unit. The first of these rough crash Rough filter their own weight (hydro-cyclone), and the second fine-sand-gravel filter, and the third was filtered parts of sand-gravel filter, the insoluble parts of very thin material, and glided in the Sieve filter fertilizer.
2. Main Pipeline: the control unit, the water main pipe side is transmitted to the main pipeline. The main pipeline of PVC, polyethylene, galvanized steel pipes can be laid, or asbestos.
3. Lateral Pipeline: water from the main, lateral conveying pipeline. Side of the main pipeline runs on the ground in some systems. In this case, the soft (polyethylene) pipes. In some systems, the pipeline runs underground in the side. In this case, the rigid pipe (PVC or galvanized steel) is used.
4) Lateral: periodically connects to the droppers soft (polyethylene or soft PVC) pipe is called the lateral line. Laterals, which goes under the soil used much more than those who go beyond the surface of the soil
Subsurface irrigation is increasing in popularity and has several theoretical and practical advantages, especially now that new pipe designs have been developed, with holes that do not easily become blocked. It is possible to operate subsurface irrigation for very short intervals, because the pipe is already located within the root zone, so effective delivery of water starts immediately. Other advantages are: there are no surface pipes to tangle equipment, there are no evaporation losses, no water is present at the surface to encourage weeds and irrigation can occur simultaneously with other management activities on the surface (eg pruning, harvesting etc). The main disadvantage of this system is that it is prone to mismanagement, as it occurs almost entirely out of view of the operator. Water is most effectively delivered in subsurface irrigation if it is delivered at high flow rates, in short bursts, to encourage lateral distribution rather than deep penetration.
The water used in irrigation of organic crop production should not cause environmental pollution. Industrial and urban waste water and drainage water from the drainage system can not be used in organic agriculture. Where necessary, the suitability of the water is decided by an authorized body in the controls. Irrigation should not lead degradation in the structure of soil and erosion.
Organic fruit growing is the main training for the healthy plant, therefore it is very important to give water at any time, at any amount that the plant needs.
Irrigation gains efficiency in fruit types and varieties, also encourages vegetative growth. It is effective in segregation and development of buds. It reduces the breakdown of fruits.
As irrigation techniques change according to the species and varieties they also vary according to the methods of soil management.
Irrigation of orchards, should be made in a way that water will not accumulate in the root zone of trees, which causes root decays in the end. Drip irrigation and mini-spring irrigation systems are the most appropriate methods for orchards.