eChapters

Introduction

 Salinity is a form of salt that occurs naturally within soils or water. When soil

becoming salty form that is called salinization, it can be caused by mineral

weathering called as natural process but it can be caused by irrigation called

as artificial process. Saline or salty soil have a high salt content like sodium

chloride (NaCl also called table salt). Salinity is like- abiotic stress for plants

and reduced the plant growth but not for all because some of them crops are

survive in better way for growth and development such as barley, sugerbeet,

cotton and mustard etc. Basically, stress are two types-biotic and abiotic

stress. Abiotic stress are also called nonliving stress like- drought, salinity,

submergence, heat, cold and temperature that are affect to plant life cycle so

that are called as abiotic stress. Natural water and all types of soil both contain

soluble salts. Amount of salt affected to weather of soil, when excessive salt

present in soil and it adversely affects to crop growth and developments. Salt

affected soils exist under arid and semi-arid climates. Major constitutions of

soluble salt in soil are the cations and anions. Cations are containing sodium,

calcium, magnesium and anions are contains chloride, sulphate, carbonate and

bicarbonate. Saline soil have <8.5 pH, >4EC (dS/m) and <15 ESP. where EC

is eclectical conductivity that is measure of soil salinity and ESP stand for

Exchangeable sodium percentage.

Soil pH

 Soil reaction is measured by pH (Puissance de Hydrogen) of a suspension of

soil in water. The word “pH” has originated from the French word “pouvoir

hydrogen” which means powers of hydrogen. The acidity, neutrality or

alkalinity of a soil is measured in terms of hydrogen ion activity (active

concentration) of the soil water system. Most of the agricultural soils have

a pH varying from 4.5 to 8.5. The active concentration of hydrogen ion is

termed as ‘active acidity’ which is 1/50,000 or 1/1,00,000 times lesser than the

exchange acidity or exchangeable hydrogen.

 Soil pH is a measure of the activity of ionised H (H+) in the soil solution. The

pH of a solution can be defined as the negative logarithm to base 10 of the H+

ion activity or the logarithm of the reciprocal of the H+ ion activity.

pH = -log10

 a[H

 +] = log10

 1/[H

 +]

 There is difference between activity and concentration. Activity and

concentration are related by the mathematical expression

 a

 c

 F

 = where a = activity of a species (moles L-1)

 c = concentration of that species (moles L-1), f = activity coefficient

 a = c for dilute solutions, f = 1

 Activity coefficient of an ionic species is the degrees of freedom of that species

to participate in an equilibrium reaction or to maintain its charge under an

ionic environment.

Introduction

 India, situated between the latitude of 08004’ and 37006’ N and longitudes of

68007’ to 97025’ E, has a geographical area of 329 Mha. Physiographically, it

can be divided into three broad regions, viz., Peninsula (a triangular Plateau in

the Deccan and South of the Vindhyas), Mountain region of the Himalalayas

(Extra-Penninsula), and the Indo-Gangetic Plain separating these two regions.

Geologically, a great part of the Penninsula is occupied by the gneiss, schists

and other rocks of diverse nature. Red soils (Alfisols) generally predominate in

this region. The western and central parts predominate in basaltic rock having

Black cotton soils of different thickness (Vertisols, Inceptisols). The mountain

region shows the development of marine sediments of all ages, especially, in

north of the Himalayas. The vast Indo-Gangetic and other plains of Pleistocene

origin are composed of alluvium of the great river systems flowing in this

region. The alluvial soils of this region depend on the age of alluvia and degree

of development.

Climatically, India shows three distinct seasons:

 i) Cool and mainly dry winters from November to February

ii) Hot and mainly dry summers from March to June

iii) Monsoon rainy season from mid-June to September.

Introduction

Soil resource catalogue provides an insight into the capability and the constraint

of mapped area for its optimum exploitation towards developmental planning.

For this motive soil survey series as an essential tool. Soil survey is essentially

a study and mapping of soils in their natural environments and systematic

examination, description, classification and mapping of soil of area.Soil survey

contains a group of compound operation involving

•             To study important properties of soils and associated land features.

 •            Define taxonomic units through correlation and classifications of soils.

•             To establish and draw a border of different kinds of soils on standard

topographical base map through mapping of soils.

 •            Transfer of technology from research farm to farmer ‘s field under

different soil condition and management practices.

Cation Exchange of Clay Minerals in Soil

The term “clay mineral” refers to phyllosilicate minerals and to minerals which impart plasticity to clay and which harden upon drying or firing. Clay minerals are layer silicates that are formed usually as products of chemical weathering of other silicate minerals at the earth’s surface. Clay minerals in soil play a significant role in exchanging cations, which are positively charged ions, and in regulating soil fertility and nutrient availability. Cation exchange capacity (CEC) is a measure of a soil’s ability to exchange cations and is influenced by the type, abundance, and charge properties of clay minerals in the soil. Clay minerals have a high CEC due to the presence of charged surfaces (silanol and alumoxane groups) that can exchange cations with the soil solution. The most common cations exchanged by clay minerals are hydrogen (H+), calcium (Ca2+), magnesium (Mg2+), potassium (K+), and sodium (Na+). When a soil solution comes into contact with clay minerals, cations in the soil solution are adsorbed or attracted to the charged surfaces of the clay particles.

Introduction

Soil aeration status involves the rate of such ventilation, as well as the proportion of pore space filled with air, The composition of that soil air and the resulting chemical oxidation or reduction potential in the soil environment. Water provides the base for food, nutritional and environmental security. Soil water plays a significant role in controlling the energy balance of the soil and its overlying micro-environment by modifying its radiation exchanges and thermal properties. Soil temperatures affect plant and microorganism growth and also influence soil drying by evaporation. It is a central maximum of ecology that “everything is connected to everything else.” This interconnectedness is one reason why soils are such fascinating and challenging objects of study. In this chapter we shall explore three aspects of the soil air, water and temperature.

Introduction

The interest in soil as a natural body originated from its ability to produce and sustain crops. The scientific study of soil probably started in the mid-nineteenth century and was dominated by geologists, chemists and plant physiologists. Justus von Liebig (1840) in his famous publication, Chemistry Applied to Agriculture and Physiology, put forward the theory that plants assimilate mineral nutrients from soils which varied in their capacity of nutrient supply. The ‘Law of Restitution’ propounded by him states that whatever is being taken by plants from the soil needs to be restored to maintain the nutrient supplying capacity of the soil.

About two-thirds of the developing world’s three billion rural people live in about 475 million small farm households, working on land plots smaller than two hectares. Many are poor and food insecure and have limited access to markets and services. Their choices are constrained, but they cultivate their land and produce food for a substantial proportion of the world’s population. Besides farming, they have multiple economic activities, often in the informal economy, to contribute towards their small incomes. These small farms depend predominantly on family labour. In China, nearly 98 percent of farmers cultivate farms smaller than 2 hectares – the country alone accounts for almost half the world’s small farms. In India about 80 to 85 percent of farmers are small. In Ethiopia and Egypt, farms smaller than 2 hectares constitute nearly 90 percent of the total number of farms. In Mexico, 50 percent of the farmers are small; in Brazil smallholders make up for 20 percent of the total number of farmers (Rapsomanikis, 2019).

Biodiversity encompasses the different kinds of life we find in one area— the variety of animals, plants, fungi, and even microorganisms like bacteria that make up our natural world. Each of these species and organisms work together in ecosystems, like an intricate web, to maintain balance and support life. Biodiversity refers to all species and living things on Earth or in a specific ecosystem. Biodiversity brings together the different species and forms of life (animal, plant, entomological and other) and their variability, that is to say, their dynamics of evolution in their ecosystems. Traditionally, there are three levels of biodiversity: genetic diversity, species diversity, and ecosystem diversity. But what does each of these levels really mean.

Stress is an intrinsic part of biological systems, and successfully adapting to stimuli that induce stress is essential for the survival of dryland crops and farm animals kept in a complex and ever-changing environment. Here the biotic stresses of crop plants are treated and not that of farm animals to avoid the expansion of the volume of the chapter. Biotic stress in plants is caused by living organisms, specifically viruses, bacteria, fungi, nematodes, insects, arachnids, and weeds. In contrast to abiotic stress caused by environmental factors such as drought and heat. Biotic stress agents directly deprive their host of its nutrients leading to reduced plant vigour and, in extreme cases, death of the host plant. In agriculture, biotic stress is a major cause of pre- and postharvest losses. Plants respond to biotic stress through a defence system (Atkinson and Urwin, 2012).

Marginal and sub marginal lands are being brought under cultivation to meet the demand of human and livestock in terms of rising demand of 6F viz., food, fodder, fuel wood, fibre and fertilizer. These in lands are unable to sustain productivity. Cultivation on such lands leads to imbalance in the ecosystem. In order to meet the above said demands and to conserve the natural resources, a diversified land use system needs to be adopted in different agro-ecological regions of the country as an alternative to conventional cropping systems. Through this approach, the biological productivity and quality of resource base of degraded lands can be significantly enhanced. Land use systems which are alternatives to crop production are called by the term ‘Alternate Land Use Systems’.

Dryland agriculture is a more vulnerable system in view of its high dependency on monsoon rains which are of aberrant nature. The risk of crop failure and poor yields always restrain farmers from investing on new technologies and input use.

Concept of resilience

Resilience is used to describe the magnitude of a disturbance that a system can withstand without crossing threshold into a new structure or dynamic. Resilience is defined as “the ability of a system and its component parts to anticipate, absorb, accommodate, or escape from unacceptable standards of living due to the effects of a hazardous event, in a timely and efficient manner”. In other words, resilience describes the capacity of communities in a given context or landscape to maintain and improve their livelihoods—despite stresses and shocks—through the sustainable management of natural resources while maintaining key ecological functions

Climate change refers to long-term shifts in temperatures and weather patterns. These shifts may be natural, such as through variations in the solar cycle. But since the 1800s, human activities have been the main driver of climate change, primarily due to burning fossil fuels like coal, oil and gas. (https://www.un.org/ en/climatechange/what-is-climate-change) While it is possible to achieve enhanced food production to meet the demands of growing populations, the prevailing negative environmental trends, if continued, might cause crises in many parts of the world (Molden, 2007). The effects of climate change on agriculture can take place through changes in average temperatures, rainfall, and climate extremes (e.g., heat waves); changes in pests and diseases; changes in atmospheric carbon dioxide and ground-level ozone concentrations; changes in the nutritional quality of some foods; and changes in sea level. (Anonymous, 2014A)

In India since ages, the dryland farmers adopted a kind of mixed farming involving traditional annual crops and livestock consisting of one or two cows / bullocks and few poultry birds. This traditional system though of small scale provided some kind of risk minimisation particularly in the years of scanty rainfall causing agricultural drought. (https://coabnau.in/uploads/1587050523_ Agriculturalheritage.pdf) Discouraged by their marginal impact on farm economy, dryland farmers switched over to the lure of ‘productive’ mono-cropping with certain commercial crops like cotton etc. The continuous mono-cropping resulted in impoverishment of soils and low crop yields which took farmers into the labyrinth of poverty.

Historical perspective: Planting of single crops or mono-cultural agriculture—is a recent invention of the industrial agricultural complex (Hirst, 2019). While unequivocal archaeological evidence is difficult to come by, it’s believed that most agricultural field systems in the past involved some form of mixed cropping. That’s because of even botanical evidence of plant residues such as starches or phytoliths of multiple crops are discovered in an ancient fields (Hirst, 2019). Mixed cropping, also known as polyculture, or co-cultivation, is a type of agriculture that involves planting two or more crop plants simultaneously in the same field so that they grow together. The primary reason for prehistoric multi or mixed cropping probably had more to do with the needs of the farmer’s family and perhaps to avoid crop failure. It’s possible that certain plants adapted to multi-cropping over time disappeared as a result of the domestication process (Hirst 2016).

Dryland agriculture limits the crop growth to a part of the year due to lack of sufficient moisture (Peterson et al., 2006). According to the Fourth five-year plan of India, dry lands are defined as areas which receive rainfall ranging from 375 mm to 1125 mm and with very limited irrigation facilities. Dry lands are economically fragile regions which are highly vulnerable to environmental stress and shocks. Degraded soils with low water holding capacities along with multiple nutrient deficiencies and depleting ground water table contribute to low crop yields and further leading to land degradation. In a country like India, 44 per cent of the total food production is supported by dryland agriculture, thereby playing a critical role in nation’s food security. With the increasing population, food production has to be increased. A real need to second green revolution has been envisioned, which can be achieved by improving the dryland agriculture.

Rainfed farming has a distinct place in the Indian agriculture, occupying 67 % of cultivated area contributing 44 % of food grains to our national food basket, supporting 40% of human and 65% of livestock population. The system is characterized by resource poor farmers, poor infrastructure and low investment in technology inputs. Even when full irrigation potential of the country is realized, 50% of the net sown area is continued to be rainfed. The important problems encountered in rainfed areas are unfavorable weather, limited choice of crops and varieties, low cropping intensity and unstable productivity. The research work done by the net work of AICRPDA (All India Co-ordinate Research Project for Dryland areas) centres and SAUs (State Agricultutal Universities) indicated that the production in rainfed environment could be enhanced by 200 % compared to the productivity of farmers’ field by adopting improved cropping systems and agro techniques.

Soil and water are the basic resources in drylands. Soil supports plant life by providing a medium for their growth and development. It is a non-renewable natural resource and susceptible to rapid degradation through various forms of erosion processes. Worldwide, around 52% of total productive land has been degraded by various kinds of degradation processes and almost 80% of the terrestrial land is affected by water erosion .Further, annually ~10 million hectares (Mha) of cropland becomes an unproductive at the global level due to soil erosion with an average rate of 30 t ha−1 year−1 soil erosion .In India, out of 328 million hectares of geographical area, 68 million hectares are critically degraded while 107 million hectares are severely eroded. Soil degradation in India is estimated to be occurring on 147 million hectares (Mha) of land, including 94 Mha from water erosion, 16 Mha from acidification, 14 Mha from flooding, 9 Mha from wind erosion, 6 Mha from salinity, and 7 Mha from a combination of factors (Battacharya et al., 2015).

Moisture deficit causing shortfalls in crop production is the characteristic feature of dryland agriculture. Other adverse factors viz., decline in soil fertility together with play of biotic stresses add to the complexities of dryland crop production. Added to the proven agronomic management to combat the problem of drought in dryland agriculture, there is the need to tailoring of suitable crop varieties which can yield reasonably well under conditions of moisture deficit (Varshney et al., 2021). In this context, the appropriate developmental rhythm along with the combination of the constellation of characters of the crop plant matching with the rainfall and the soil moisture availability patterns of the zone are the important considerations together with stability of yield (Hanson and Nelsen, 1980). This task being a complex one, the problem should be approached through multidisciplinary strategy that should buffer the genetic and breeding efforts.

The world’s drylands include hyper-arid, arid, semi-arid and dry sub-humid areas where rainfall is highly scanty and variable. Droughts are common in areas / zones where water is the principal limiting factor for agriculture (https:// www.fao.org/3/t0122e/t0122e03.htm) . Dryland soils are characterized by low levels of moisture, organic matter, and biological activity, consequently such soils are very poor in fertility devoid of plant nutrients. When, these soils suffer further degradation in fertility, resulting in erosion, desertification, and salinization when crops are grown on such soils inappropriately without any scientific basis. However, the major factor limiting agricultural production on drylands is the lack of adequate moisture for crop growth or drought.