Innovations in Utilization of Poor-Quality Water for Sustainable Agricultural Production

Abstract

To meet the requirements of food and other agricultural commodities for the burgeoning population is a big challenge for the agricultural community. With the increasing demand for good-quality land and water for urbanization and development projects, agriculture will be pushed more and more to the marginal lands, and the use of poor-quality waters for irrigation is inevitable. Groundwater aquifers in the most of arid and semiarid regions are saline, and therefore cultivation of conventional arable crops with saline irrigation has not been considered sustainable in these regions. However, concerted research efforts have shown that the degraded lands can be put to remunerative alternative uses (through agroforestry) including salt-tolerant forest and fruit trees, crops, forage grasses, medicinal and aromatic and other high-value crops, and adopting appropriate planting (e.g., subsurface planting) and other management techniques (furrow irrigation). Such uses have additional environmental benefits including carbon sequestration and biological reclamation. Agroforestry is not only a necessity for increasing tree cover and hence decreasing pressure on natural forests but also a most desired land use especially for reclaiming and rehabilitating the degraded lands, especially in arid and semiarid rainfed areas underlain with saline groundwater as source of irrigation. In developing countries like India, there seems to be little scope for bringing the fertile lands under forest cover. It may be emphasized that we can bring unproductive wastelands and waterlogged areas under forest cover and take agroforestry tree plantation on non-forest community and farmlands utilizing poor-quality water including drainage and wastewaters. The long-term studies conducted show that salt-affected and waterlogged areas and saline water (including seawater) can be utilized satisfactorily in raising forest and fruit tree species with improved techniques, forage grasses, conventional and nonconventional crops, oil-yielding crops, aromatic and medicinal plants of high economic value, petro crops, and flower-yielding plants.

Out of 356 km³ years⁻¹ of total wastewater generated across all the continents, only 50 % is treated to primary level. In developing countries of the Middle East and North Africa (MENA), Latin America, and Asia, only 8 %, 18 %, and 32 %, respectively, of total wastewater generated is treated. Overall, about 20 million hectares of agricultural land is irrigated with treated and untreated wastewater throughout the world. Such practice has resulted in the potential health risks due to pathogen, salt, nutrient, and toxic element contamination of the food chain and environment. Controlled irrigation of wastewater, in plantations based on water, nutrient, and pollutant (metals) assimilation capacity, can help in productive utilization and safer disposal of wastewater. Several tree species have the potential to accumulate appreciable concentrations of Cd, Cu, Ni, and Zn in their root tissues when irrigated with wastewater or grown on metal-contaminated soils. In woody species, additional wood and bark formed every year are important sinks for biologically available metals. Since these tissues are slow to enter the decomposition cycle, accumulated metals remain immobilized for a considerable longer period. Urban plantations and green areas with nonedible crops like cut flowers and aromatic grasses in combination with constructed wetlands also offer many economic, social, recreational, and biodiversity conservation benefits over its use in agriculture and disposal in water bodies. Opportunities for raising nonconventional but remunerative crops and alternate land uses through use of saline underground and wastewaters are discussed in this chapter.