Irrigation productivity and the future n Global irrigation
Irrigation, productivity and the future n Global irrigation in early 1990’s: F 16% of total cropland F 36% of total harvest n Irrigation’s contribution to increased production n (seeds, water, fertilisers, agrochemicals) n Uses about 65% of total available freshwater, and expected to decline to 60%in Y 2 K.
Irrigation, productivity and the future (contd) n Contributed more than 1/2 of productivity gains since 1970 n Asia: 2/3 of food supply from <1/2 of cultivated area. n 40% of all agricultural production from 20% of arable land in developing countries (Seregeldin 1996) n 46% grain, 57% total value of wheat and rice in developing countries produced under irrigation in 1990. n See overhead of production and arable area
The future of irrigation? n 1960 - 1980: buoyant investment in irrigation projects n (high yielding varieties, and good grain prices) n between 1961 and 1982 - £ 500 bn (‘ 95 prices) n However, there has been a decline in investment due to: F fall in grain prices F real costs of irrigation increased F thus low rates of return F low efficiencies of projects F growing competition for freshwater (65%) F environmental concerns
The future of irrigation? n The future of large-scale funding seems to be giving priority funding the improvement of existing irrigation systems n However, the future of irrigation and water provision both seem to be intricately linked to the ability of agriculture to feed the human population n See overhead of human population and n overhead of water provision scenarios
Choice of irrigation systems: (Is it worthwhile irrigating? ) n n n n climate and soils topography water supply crop types labour legal aspects Other issues: Ffarmer training available, pests, machinery: spares and mechanics? ,
Choice of irrigation systems: n climate and soils n topography Fwill affect choice of irrigation method, height of fields compared to water supply, use of pumps, levelling costs, n water supply Felevation, distance, quality, cost, quantity of water required is frequently underestimated, need to consider seasonal availability and maximum demand n crops Fmay have to introduce new crops- will they sell? FIs the price of crop > irrigation costs?
Choice of irrigation systems: n labour Fmore intensive than rain-fed cultivation, small farmslittle added labour, more tied to land n legal aspects Fmany countries have legislation governing the use of limited water resources, common rights, upstream uses n Other issues: Ffarmer training available, pests, machinery: spares and mechanics? ,
Soil and Water Conservation n “Runoff agriculture provides moisture by collecting surface/subsurface runoff where other sources are likely to too costly, unsustainable or damaging. “ n “Concentration of surface runoff for cultivation” n Effectively uses moisture that would otherwise go to waste (unavailable to agriculture) n Characteristics and advantages of runoff farming: F cheap to establish F uses local materials (remote areas) F a sustainable practice F improved harvest security F improved yields, more crops per year F improve quantity and quality of streamwater and groundwater recharge
Soil and Water Conservation n Agronomic techniques F Mulching F plastic sheets underground F soil amendments F Fallowing F Conservation tillage n Mechanical techniques (devices that act as cross-slope barriers F trash lines F stone lines F wattling/staking F contour bunds, hillside ditches, soil pits, terraces
Soil and Water Conservation n Vegetative techniques F plant cover F agroforestry n Fog and mist harvesting F 150 -750 litres per day from 48 m 2 mesh trap F Further reading: F Barrow 1987 F Hillel 1997 F Stern 1979
- Slides: 10