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Water and Agriculture

Water and Agriculture

(s.parthasarathy, ug agrl student, faculty of agriculture ,annamalaiuniversity)

Food security in future is a major issue, which is increasingly being discussed across the world. The increase in food production in future is very much dependent on water availability, as water is major component of all food products. The demand for the scarce resource water is rising rapidly, challenging its availability for food production and putting global food security at risk. Will there be enough water to grow food for almost 8 billion people expected to populate the Earth by 2025? It is almost impossible to answer, without understanding the evolving relationship between water availability and food production.

Food and Agriculture Organisation (FAO) estimates that the world contains about 1400 million cubic km of water, out of which only 2.5% (35 million cubic km) is freshwater. Freshwater, which is available for use of human being and agriculture is also a negligent percentage of total fresh water. Fresh water that can be used stems essentially from rainfall over land, generated through the hydrological cycle.

Agriculture is by and far the largest user of water, accounting for about 69% of all withdrawals. Industry and municipalities consume about 21% and 10% respectively of total water withdrawn. It is necessary to know the concept of water withdrawn and water consumed. Out of the 3600 cubic km water withdrawn annually, half of it is consumed as a result of evaporation and transpiration from plants. Water, abstracted but not consumed, flows back over the surface to rivers or infiltrates the ground and get stored in aquifers. However, this water is generally of a lower quality than the water that was withdrawn. Irrigation consumes much of the water it withdraws (often half or more) as a result of evaporation, incorporation into crops and transpiration from crops. The other half recharges groundwater or surface flows or is lost in unproductive evaporation

FAO's recent report World agriculture: towards 2015/30 projects that global food production will need to increase by 60% to close nutrition gaps, cope with the population growth and accommodate changes in diets over the next three decades. Water withdrawals for agriculture are expected to increase by about 14% in that period, representing an annual growth rate of 0.6%, down from 1.9% in the period 1963-1999. Much of the increase will take place on arable irrigated land, forecast to expand globally from some 2 million sq. km to 2.42 million sq. km. In a group of 93 developing countries, water use efficiency in irrigation - the ratio between water consumption by crops and the total amount of water withdrawn - is expected to grow from an average 38% to 42%.

Productivity of water used in agriculture has increased by at least 100% in last four decades, which is mainly because of increase in crop yield. Irrigated rice yields doubled and rain-fed wheat yields rose by 160% in that period, with little variation in water consumption per kilo of output. Globally, FAO estimates that water needs for food per capita halved between 1961 and 2001, a significant saving and an equally significant gain for other water users. It is estimated that a rise in 1% in water productivity in food production makes available an extra 24 litres of a day per head of population, while a 10% increase would equal current domestic water consumption.

Though the water use efficiency in agriculture has increased, there are still some areas where attention is required. At farmers' level, higher water productivity require changes in crop, soil and water management. Farmers should select appropriate varieties of crop, use improved planting methods, use minimum tillage farming practices, synchronise the water applications with the most sensitive growing periods and improve the drainage for water table control. The concerned government department should also spread proper information about the methods, practices and technologies, which if use, can increase water productivity.

A recent study by the International Food Policy Research Institute (IFPRI) and the International Water Management Institute (IWMI) projects that if present trends continue, by 2025 competition from growing cities and industry worldwide will limit the amount of water available for irrigation, causing annual global losses of 350 million metric tons of food production. The research done in past shows that by improving productivity of water on irrigated and rain-fed lands can make available enough water for cities, industry and nature.

Irrigated agriculture, though practiced in 20% of land, has driven most of the increase in global food production, contributing 40% of the global food supply. As per FAO report, the highest yield obtained from irrigated agriculture is more than double the highest yield of rainfed agriculture. Globally rainfed agriculture is practiced in almost 80% of the cultivated land and supplies more than 60% of the world's food. Improving water productivity of the 16000 cubic km of water used in rainfed agriculture should get equal importance to the 2500 cubic km water diverted to irrigation. A study shows that one-percent increase in rain-fed cereal production would have one and half times more effect than a similar productivity increase in irrigated cereal production.

There is no single and exclusive solution to increase productivity of water - more crop per drop. Hence, all stakeholders of water use should use integrated strategies tailored to local conditions to enhance the efficiency of water use. There are few solutions, which are outlined below, can be integrated to get the best results.

Crop breeding: Till 1980s, crop breeding has increased the productivity of water by increasing yield without increasing crop water demand. The focus has primarily been on getting more yield per unit of land. It is only in the past decade that attention has turned to producing crops that can yield more with less water, withstand water-scarce conditions, and thrive on low- quality (saline/alkaline) water. The Future Harvest Centers of the CGIAR have already released drought-tolerant varieties of several crops for evaluation by collaborating institutes and farmers.

Reducing Land Degradation: Soil erosion can reduce the water holding capacity of soil because of removal of top soil. The degradation of agro-ecosystem is very difficult to regain by external application of inputs. Hence, farmers should be given incentives to make long-term investments in soil conservation practices-particularly when results from such investments do not have a direct or significant impact on their incomes.

Supplemental and Deficit Irrigation and Water Harvesting for Rainfed Areas: Supplemental irrigation combined with on-farm water-harvesting practices, such as mulching or bunding, reduces vulnerability to drought and helps farmers to get maximum use of scarce resources. Deficit irrigation-a strategy which maximises the productivity of water by allowing crops to sustain some degree of water deficit and yield reduction-holds promise for severely water-short areas, such as North Africa and the Middle East countries. As per a study done by International Center for Agricultural Research in the Dry Areas (ICARDA) in Syria, the yield reduces only by 15% by the application of 50% of the supplemental irrigation requirement.

Low-cost Technologies: Farmers should adopt low-cost precision irrigation technologies such as sprinkler and drip depending on crop and other conditions, which can reduce the wastage of water. Drip irrigation is a pressurised system that forces water through perforated pipes running above ground just around the roots of plant. The development of sprinkler and drip irrigation in India has been considerable in last few years mainly due to pressing demand of water from other sectors which has forced government to promote water saving irrigation techniques. It is being estimated that more than 2 lakh sprinkler systems were sold between 1985 to 1996. The area under sprinkler irrigation can be estimated 0.7 million hectare in 1996. The cost of installation of sprinkler irrigation depends upon number of factors such as type of crop, the distance of the water source, spacing, and nature of terrain. The approximate capital cost (excluding pump cost) ranges from US $ 450 (Rs.22, 000) to US $ 560 (Rs. 27,000) per hectare.

Similarly, the area under drip irrigation has also increased tremendously, from 1000 ha in 1985 to 70,860 ha in 1991, mainly in Maharashtra, Andhra Pradesh and Karnatka. The drip-irrigated crops are mainly orchard crops such as grapes, banana, pomegranate, and mango. The average cost of drip irrigation development ranges from US$ 750 (Rs. 36,000) to US$ 2000 (Rs. 96,000) per hectare.

Agronomic and Field Practices: Conservation or zero tillage, optimal use of fertiliser and water and other form of soil-water management can raise the productivity of water. Other agronomic practices such as alternate row irrigation, raised beds & furrows, mulching & residue management, direct seeding of rice and timely planting can be practiced by farmers depending on the crop and climatic situation to enhance the water productivity. Positive Role of Policy, Institution and Incentives: Farmers need incentives to adopt new technologies and practices, which show late results. Hence the concerned government should give incentives to make it easily accessible, such as some state governments in India provide subsidy up to 90% in case of drip and sprinkler irrigation equipment. Considering the importance of water resources, India adopted a national water policy in 1987 for the planning and development of water resources to be governed by national perspectives. It emphasises the need for river basin planning. Water allocation priority has been given to drinking water, followed by irrigation, hydropower, navigation and industrial or other uses. Recently, Government of India has set up a task force on Interlinking of Rivers to share excess or shortages of flood water and thus reducing regional imbalance in the availability of water.

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Please note that this is the opinion of the author and is Not Certified by ICAR or any of its authorised agents.