Coping with salinity in irrigated agriculture: crop evapotranspiration and water management issues

ReviewSoil and water salinity and associated problems are a major challenge for global food production. Strategies to cope with salinity include a better understanding of the impacts of temporal and spatial dynamics of salinity on soil water balances vis-à-vis evapotranspiration (ET) and devising optimal irrigation schedules and efficient methods. Both steady state and transient models are now available for predicting salinity effects on reduction of crop growth and means for its optimization. This paper presents a brief review on the different approaches available, focusing on the FAO56 framework for coping with the effects of soil salinity on crop ET and yields. The FAO56 approach, applied widely in soil water balance models, is commonly used to compute water requirements, including leaching needs. It adopts a daily stress coefficient (Ks) representing both water and salt stresses to adjust the crop coefficient (Kc) when it is multiplied by the grass reference ETo to obtain the actual crop ET values for saline environments (ETc act=Ks Kc ETo). The same concept is also applied to the dual Kc approach, with Ks used to adjust the basal crop coefficient (Kcb). A review on applications of Ks is presented showing that the FAO56 approach may play an interesting role in water balance computations aimed at supporting irrigation scheduling. Transient state models, through alternative formulations, provide additional solutions for quantification of the salinity build-up in the root zone. These include irrigation-induced salinity, upward movement of salts from saline ground water-table, and sodification processes. Regardless of the approach, these models are now very much capable of supporting irrigation water management in saline stress conditions. For maintaining crop growth under salinity environments, soil-crop-water management interventions consistent with site-specific conditions are then discussed. Adequateness of irrigation methods, cyclic uses of multi-salinity waters and proper irrigation scheduling are further analyzed as examples of efficient means to obviate the effects of salinityinfo:eu-repo/semantics/publishedVersio

Wastewater use in agriculture: saline and sodic waters

In Trimble, S. W. (Ed.). Encyclopedia of water science. New York, USA: Taylor & Franci

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Not AvailableSugarcane is an important industrial crop cultivated in India with the production of almost 300 million tones. In the recent years, farmers and sugar industry are concerned about the frequent occurrences of flowering in fields' sugarcane. Because it is highly undesirable trait, which affects crop productivity and sugar content. Apart from many of plant physiological and climatic variability factors, the rhizosphere microbial diversity and their functional activities on plant nutrition also play a key role in inducing flowering in sugarcane. Few of the recent studies indicated that continuous mono- /ratoon cropping and post harvest field burning of sugarcane trashes having negative impact on rhizosphere diversity and function. The present report is an attempt to explain the possibility of prevention of flowering in fields' sugarcane with emphasis on preserving/ managing the native soil microbial diversity for better nutrition and growth of crops.Indian Council of Agricultural Research, New Delh

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Not AvailableThe continuous surge in irrigation, particularly using groundwater for sustaining food security in many developingc countries, has necessitated the utilization of low-quality waters especially in water-scarce arid and semiarid regions. Inappropriate irrigation with these waters results in land and environment degradation produced by associated salts, sodium and other toxic elements. Generally the soil’s sodification process is insidious and build-up of exchangeable-Na is initially gradual. It stabilises at levels governed by sodicity indices of irrigation water, soil type, cropping sequences and agro-climatic conditions. As the soils become sodic, crop productivity declines and ultimately soils can become unsuitable for cropping. As a result, cultivators are forced to opt for tolerant crops, which are typically of less economic value. To minimize harmful effects of sodicity, remedial measures have been developed at the crop, root zone, farm and district/basin levels. These include water quality driven conjunctive uses, chemical amelioration of soils and irrigation waters, mobilising native calcite through phyto-remediation, growing tolerant crops, and other specialised tillage, fertiliser use and irrigation practices. This review seeks to critically analyse the role of these measures and the crop, water and soil factors defining the sodification vis-à-vis infiltration problems. The conclusions provided here are expected to be helpful for a range of stakeholders to promote irrigation with sodic/alkali waters, thereby partly alleviating the forecasted scarcities in water for agriculture

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Not AvailabletSince irrigation with under-treated wastewater is growing in many underdeveloped countries, its reg-ulation should follow more efficient and less polluting approach. Therefore, the nutrient balances andsoil properties were monitored in an 8-year experiment where the food grain (FGPS, paddy–wheat),fodder (FPS, sorghum-Egyptian clover) and vegetable (VPS, gourds/okra-cabbage/cauliflower) and agro-forestry (AFS, poplar–paddy–wheat) production systems were irrigated either with sewage water (SW,BOD 82 ± 11, NO3–N 3.2 ± 0.4, NH4–N 9.6 ± 0.5 and P 1.8 ± 0.3 mg L−1) or good quality groundwater (GW)along with variable doses of N & P (25–100% of the recommended). The concentration and uptake of bothN and P increased with SW and NP doses. SW enhanced N uptake by 29, 23, 18 and 37% in FGPS, AFS, FPSand VPS, respectively, while the corresponding values were 28, 21, 29 and 35 per cent for P uptake. Thecrop N removal obtained at 100% NP dose in GW were at par with 25% NP doses in AGF and VPS and 50%NP doses in FGPS and FPS with SW. The positive balances of nutrients with SW resulted in improvementin soil organic carbon and available status of nitrogen and phosphorus. Soil microbial biomass carbon(MBC) and activities of dehydrogenase, urease and phosphatase also improved substantially with SW.The most of nitrate-N was retained in the surface 0.3 m soil especially its leaching was minimal under AFS.Overall results indicated for improvement in the awareness of the growers for adjusting NP doses andnon-dependent on water guzzling crops like paddy to minimise the fertiliser costs and the contaminationof groundwater.Not Availabl

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Not AvailablePlant growth and productivity are stimulated by plant bio-regulators (PBRs), which are biochemical compounds that are applied even in small quantities at appropriate plant growth stages. To enhance the productivity, particularly, PBRs are being extensively used in agriculture and horticultural crops. Though nutrient allocation and source-sink transitions have their central role in plant growth and development and, most of the PBRs stimulate redox signaling under abiotic stress conditions. Since climate change and degrading natural resources are projected to amplify the stresses, particularly soil moisture deficit, high temperature, and soil salinity, PBRs are likely to play a crucial role in plant growth regulation under these stress conditions. However, critical evaluation should consider the utility of PBRs to enhance crop productivity under stresses induced by abiotic factors. Research efforts so far have centered on the crop and agroecosystem specificity, optimal doses, and schedule of their application for optimizing crop yields under stress conditions. These efforts are being complemented by investigations on genes and gene regulatory network at molecular level to tailor crop plants for climate resilience. In addition to complying with regulation governing the use of biochemicals, case studies related to crop yield in major cereals are also reported. In this chapter, prospects and pathways of PBRs are described as an emerging stress-alleviating technology for crop production in harsh agroecosystems, specifically those featured by drought, heat, and salinity stress.Not Availabl