Soil Salinity Management in Agriculture

Technological Advances and Applications

S. K. Gupta, Megh R. Goyal, S. K. Gupta, Megh R. Goyal

• Publisher: Apple Academic Press
• Year: 2017
• ISBN:
  9781315341774
• Edition: 1
• Topic: Scienze biologiche
• Subtopic: Scienza generale

This important volume, Soil Salinity Management in Agriculture, addresses the crucial issue of soil salinity of potential farmland and provides a comprehensive picture of the saline environment and plant interactions, along with management and reclamation methods and policies. With contributions from researchers from the fields of agricultural chemistry, soil science, biotechnology, agronomy, environmental sciences, and plant breeding and genetics, the volume emphasizes a multidisciplinary approach.

PREFACE 1 BY S. K. GUPTA

Soil salinity, an incipient problem, comes to the fore only when some damage has already been done. Besides adverse impacts on agricultural productivity, the consequences of soil salinization can be quite damaging. Civilizations in southern Mesopotamia and in several parts of the Tigris–Euphrates valley were wiped out in the past because of water logging and soil salinity. Damages in the Aral Sea Basin are the living example of how things can go wrong with improper land and water management practices. There are other basins in Australia, China, India, Pakistan, and the United States that are grappling with salt related land and water degradation.

Soil and water salinity adversely affect on-farm, regional and national interests having a major impact on food security, land, and water quality and environment resulting in serious economic and social problems in rural and urban communities. There are wide variations in the figures of the extent of the area affected by soil salinity from one assessment to another yet the sizable area in different continents especially in irrigated lands is causing concerns in more than 100 countries around the globe. With many intersecting challenges such as climate change, deforestation, and fresh water shortages resulting in the exploitation of saline water in agriculture, soil salinity is posing unprecedented dangers to the sustainability of agricultural systems and the environment. Learning from what went wrong coupled with scientific innovations, understanding of the natural and anthropogenic causes, and prevention and reclamation of salt affected lands has hugely improved. Catastrophic losses experienced in the past can easily be avoided if the current knowledge on the subject gets translated into scientifically proven field practices. Advancements in researches as well as application of research results in this multi-disciplinary arena require an inter-disciplinary approach drawing knowledge and experiences of the experts from soil science, agronomy, engineering, hydrology, other water sciences, plant sciences, environmental sciences, modelers, Preface 1 by S. K. Gupta and computer sciences. Equally crucial would be the stakeholder participation in the field applications of these technologies.

The current volume Soil Salinity Management in Agriculture: Technological Advances and Applications under Innovations in Agricultural and Biological Engineering has been designed keeping all these issues in view to provide readers a comprehensive picture of the saline environment and plant interactions. The chapters in the current volume have been written by experts in their respective sphere, and cover major issues related to salinity management in agriculture. The editors for the sake of convenience have grouped these chapters into three sections namely:

I.	Emerging Trends and Technologies in Salinity Management
II.	chapters into three sections namely:Mechanisms of Salt Tolerance
III.	chapters into three sections namely:Soil Salinity Management in Crop Production

Part I with four chapters dwells upon emerging trends and technologies in salinity management in soils or water covering arid, semi-arid and coastal eco-regions. While the first chapter by Sharma and Singh deals with the emerging trends of salinity research in India. The included technologies and practices have the replication potential in many developing and developed countries as many cost-cutting techniques including use of industrial wastes in land reclamation programs are included. The second chapter specifically deals with similar issues related to use of saline water in agriculture. It advocates living with salts which may be the only option when reclamation is either expensive or impractical to adopt. The coastal ecosystem have the high potentiality of production of a large number of goods and services valued at about US$ 12–14 trillion annually, and is confronted with high risk of soil salinization due to the multiple issues including the climate change—is the theme of discussion by Sen and Ghorai. In recent times, ground water salinity and its pollution has assumed serious overtones around the globe because of its use across many economic sectors. Unlike surface waters, to pinpoint the sources of contamination of ground water could be a major challenge for the ground water management and planning. The chapter by Machiwal and Jha briefly reviews the past technologies and describes the recent advances made in this vital arena of salinity management in agriculture.

Plants when exposed to salt stress activate their salt tolerance mechanisms through stress sensing and signaling so as to regulate the plant salinity stress response. For example, some halophytes respond to salinity by taking up sodium and chloride at high rates and then accumulating these ions in their leaves. Many glycophytes respond to stress by salt exclusion particularly through low rates of net transport of sodium or chloride, or both from root to shoot. Plant adaptations to salinity have been categorized into three types, namely osmotic stress tolerance, Na⁺ or Cl⁻ exclusion, and the tolerance of plant tissues to accumulated Na⁺ or Cl⁻.

Part II deals with these and similar issues in various plants types. The chapter by Gururaja Rao et al. lists some of the technological interventions to green the barren saline Vertisols using Salvadora persica, a facultative halophyte, a potential source for seed oil, and some forage grasses. Four grasses namely Dichanthium annulatum and Leptochloa fusca for saline water-logged soils, and Aeluropus lagopoides and Eragrostis species for saline water-irrigated lands have been included. Ramana et al. argue that not much is known about the abiotic stress responses of Plectranthus species grown for their ethno botanical use as ornamental, medicinal and economic plants. This chapter looks at the impacts on morphology, physiology and biochemical processes in the six genotypes of Plectranthus species to arrive at their suitability for cultivation in saline environment. Desmukh and Khare in their chapter argue that as per the estimates of World Health Organization (WHO), nearly 80% of the world populations rely on medicinal herbs, the requirement of which can be met only through commercial cultivation of medicinal plants. Since land is already a constraint to meet the food demand, it is the otherwise problem soils and/or harsh climatic conditions under which these plants will have to be cultivated. As such, their chapter reviews the current status of studies conducted to assess the effect of salinity stress on growth parameters and metabolites of medicinal plants.

Reclamation and sustainable crop production on reclaimed lands has been the major thrust area of research in salinity management in agriculture. Part III deals with this theme and related issues includes five chapters wherein application of emerging technologies and stakeholders participation in sustainable land reclamation programs is highlighted. Biological reclamation of salt affected lands, a low cost eco-friendly approach, is emerging as a new thrust area of research where plants and microbes are increasingly used to reclaim these lands. A comprehensive review of bacterial-mediated amelioration processes in plants under salt stress has been made by Kasotia and his colleagues. Singh argues that the lack of success of many breeding programs in developing commercially successful salt tolerant crops is due to limited evaluation of genetic material in idealized conditions that does not represent the actual field situations. Sustainable land reclamation using salt tolerant cultivars developed through farmers’ participatory approach is the subject matter of discussion by him. Pokkali rice cultivation has passed down from one generation to another generation from more than 3000 years; and this has been discussed in the framework of symbiotic nature of rice and shrimp cultivation. This strategy helps to manage lands experiencing multiple stresses due to water logging, soil salinity, and irrigation water salinity, a common feature of the coastal ecosystems.

One of the important limiting factors for optimal use of land resources for higher productivity especially in sub-humid and humid regions is soil acidity—acid soils occupying about 3.95 billion ha globally. The chapter by Chaitanya et al. presents comprehensive technological interventions to manage such lands including the acid sulfate soils. Yaduvanshi, in the last chapter of this volume, has emphasized that limited nutrient availability in salt affected the soils. As a result of host of unfavorable physico-chemical conditions, the production potential of reclaimed lands as well as impacts the sustainability of the program. He emphasizes that appropriate prescription of macro and micro-nutrients, in right quantities, at the right time and place, from the right source, and in the right combination could play a major role in sustaining the reclamation benefits.

I believe that the salinization of the land and water is now a very serious threat to the health and utility of soil, vegetation, rivers and ground water around the world. Considering the looming food security crisis of the 2050, no let-up can be allowed in our efforts to understand salt tolerance mechanisms, develop new technologies and apply the existing ones for prevention, living with salts and/or sustainable land reclamation programs can be allowed. This volume may give the readers a good feel of the efforts being made in these respective areas.

I take this opportunity to thank all the contributors for sparing their valuable time and painstaking efforts made in preparing timely submission and updating their edited manuscripts in a time bound manner to make timely publication of this volume possible. I believe that the current volume will serve as a good repository of latest information and will be highly useful to researchers, policy planners, teachers, students especially the post graduate students, development agencies and other who are interested in salinity management for resolving global food security issues and its relationship with the environment. Finally, I thank the editorial staffs who have been involved in this project.

—S. K. Gupta, PhD

Lead Editor

PREFACE 2 BY MEGH R. GOYAL

According to https://en.wikipedia.org/wiki/Soil_salinity, the soil salinity is the salt content in the soil; and the process of increasing the salt content is known as salinization, which can be caused by natural processes (mineral weathering or by the gradual withdrawal of an ocean) or through artificial processes such as irrigation. The ions responsible for salinization are: Na⁺, K⁺, Ca²⁺, Mg²⁺, and Cl⁻. As the Na⁺ (sodium) predominates, soils can become sodic. Sodic soils present particular challenges because they tend to have very poor structure, which limits or prevents water infiltration and drainage. Over long periods of time, as soil minerals weather and release salts, these salts are flushed or leached out of the soil by drainage water in areas with sufficient precipitation. In addition to mineral weathering, salts are also deposited via dust and precipitation. In dry regions, salts may accumulate leading to naturally saline soils. Human practices can increase the salinity of soils by the addition of salts in irrigation water. Proper irrigation management can prevent salt accumulation by providing adequate drainage water to leach added salts from the soil. Disrupting drainage patterns that provide leaching can also result in salt accumulations. Salinity in drylands can occur when the water table is between two to three meters from the surface of the soil. The salts from the ground water are raised by capillary action to the surface of the soil. This occurs when ground water is saline (which is true in many areas), and is favored by land use practices allowing more rainwater to enter the aquifer than it could accommodate. Salinity from irrigation can occur over time wherever irrigation occurs, since almost all water (even natural rainfall) contains some dissolved salts. When the plants use the water, the salts are left behind in the soil and eventually begin to accumulate. Since soil salinity makes it more difficult for plants to absorb soil moisture, these salts must be leached out of the plant root zone by applying additional water. This water in excess of plant needs is called the leaching fraction. Salinization from irrigation water is also greatly increased by poor drainage and use of saline water for irrigating agricultural crops. The consequences of salinity are: detrimental effects on plant growth and yield; damage to infrastructure (roads, bricks, corrosion of pipes and cables); reduction of water quality for users, sedimentation problems; soil erosion ultimately, when crops are too strongly affected by the amounts of salts. Salinity is an important land degradation problem. Soil salinity can be reduced by leaching soluble salts out of soil with excess irrigation water. Soil salinity control involves water table control and flushing in combination with tile drainage or another form of subsurface drainage. A comprehensive treatment of soil salinity is available from the United Nations Food and Agriculture Organization. High levels of soil salinity can be tolerated if salt-tolerant plants are grown. Sensitive crops lose their vigor already in slightly saline soils, most crops are negatively affected by (moderately) saline soils, and only salinity resistant crops thrive in severely saline soils.

According to “R. Brinkman (1980), Saline and Sodic Soils. In: Land reclamation and Water Management, pp. 62–68. International Institute for Land Reclamation and Improvement (ILRI), Wageningen, The Netherlands,” the salinized areas (in million ha) are: 69.5 in Africa; 53.1 in Near and Middle East; 19.5 in Asia and Far East; 59.4 in Latin America; 84.7 in Australia; 16.0 in North America; and 20.7 in Europe.

One can download free the LeachMod software for simulating leaching of saline irrigated soil from http://www.waterlog.info/leachmod.htm. LeachMod is designed to simulate the depth of the water table and the soil salinity in irrigated areas with a time step as selected by the user (from 1 day to 1 year). The program uses small time steps in its calculations for a better accuracy. In case of a leaching experiment with measured soil salinities, LeachMod can automatically optimize the leaching efficiency by minimizing the sum of the squares of the differences between measured and simulated salinities. The root zone can consist of 1, 2, or 3 layers. LeachMod allows the introduction of a subsurface drainage system in a transition zone between root zone and aquifer, and subsequently it determines the drain discharge. When the irrigation/rainfall is scarce and the water table is shallow, LeachMod will calculate the capillary rise and reduce the potential evapotranspiration to an actual evapotranspiration. LeachMod can also take into account upward seepage from the aquifer or downward flow into it. The latter flow is also called natural subsurface drainage. This model is somewhat similar to SaltCalc. On one hand, the water management options are fewer (e.g., re-use of drainage or well water for irrigation do not feature here), but the model is more modern in the sense that the variable input for each time step is given in a table so that the calculations over all the time steps are done at one step. Moreover, by inserting the observed values of soil salinity in the data table, the model optimizes the leaching efficiency of the soil automatically. On 11 July 2015, LeachMod was updated to include more rigorous data checks.

I know what the cooperating authors have emphasized in their chapter for this book volume. I am a staunch supporter of preserving our natural resources. Importance of wise use of our natural resources has been taken up seriously by Universities, Institutes/Centers, Government Agencies and Non-Government Agencies. I conclude that the agencies and departments in soil salinity management have contributed to the ocean of knowledge.

This book also contributes to the ocean of knowledge on soil salinity management. Agricultural and Biological Engineers (ABEs) with expertise in this area work to better understand the complex mechanics of soil salinity. ABEs are experts in agricultural hydrology principles, such as controlling drainage, and they implement ways to control soil erosion and study the environmental effects of sediment on stream quality.

The mission of this book volume is to serve as a reference manual for graduate and undergraduate students of agricultural, biolo...