eChapters

Introduction

Trees play an important role in ecosystem in all terrestrials and provide a range of products and services to rural and urban people (Gogoi 2015). As natural vegetation is cut for agriculture and other types of development, the benefits that trees provide are best sustained by integrating trees into agricultural system - a practice known as agroforestry. Agroforestry focuses on the wide range of trees grown on farms and other rural areas. Among these are fertilizer trees for land regeneration, soil health and food security; fruit trees for nutrition; fodder trees for livestock; timber and energy trees for shelter and fuel wood; medicinal trees to cure diseases and trees for minor products viz. gums, resins or latex products. Many of these trees are multipurpose, providing a range of benefits. Although effective and valuable tools have been introduced to evaluate the risk to construction in areas prone to geo-hydrological hazards, fewer steps have been made in the field of ordinary land use planning at different scales. 

Introduction

The world demand for wood is continuously increasing due to increase in population. The ever increasing population has led to depletion of existing timber reserves and the forestland base has been reduced by increased allocation of forest areas to urban, agricultural, recreational and other uses. The growing awareness towards development of plantations has generated a voluminous increase in the demand for quality planting material. Conventionally, propagation is achieved through sexual (seeds) or vegetative methods (rooting of cutting, grafting, layering, etc). Propagation through seeds is routinely used for production of planting material but it generates immense genetic variability which is not desirable while propagating perennial tree species. In order to propagate selected trees with desirable features vegetative propagation methods like rooting of cuttings, grafting, layering etc have been developed. These methods can produce genetically identical off springs thereby preserving the advantageous traits;

Introduction

Desertification is affecting the livelihoods of millions of people, mainly poor in the dry lands, which occupy nearly 41% of the Earth’s land area and are the residence of more than 2 billion people of the world. In India, the western part of Rajasthan is mostly affected by desertification process dominated by wind erosion. Kar et al. (2009) reported that 15.2 mha land in western Rajasthan is affected by wind erosion out of total 22.96 mha area under desertification. A brief account on issues and priorities related to wind erosion processes in Thar desert was reported in Santra et al. (2006). Plenty of incident solar energy in the region makes the desert surface very hot especially during summer months. Wind speed also remains very high in the region for most of the time in a year. Therefore, the loss of top fertile soils through wind erosion process is very active in the region. Eroded dust particles during severe wind erosion events commonly known as dust storms not only create the soils poor but also pose several environmental threats through generating aerosols in atmosphere. 

Introduction

The area under salt-affected soils in India is estimated to be 6.73 Mha spread over a number of states across the country. This 6.73 million ha are lying barren or produce very uneconomical yields of crops due to excessive accumulation of salts. These soils are agriculturally unproductive because of the high content of soluble salts which had harmful effects on plant growth due to moisture stress and toxicity/deficiency of some of the ions and the exchangeable sodium ions in clay complex lead to the unfavorable physical conditions of for the plant growth and water movement (Bhumla 1977). Saline and sodic soils have excess concentration of either soluble or exchangeable sodium, calcium and magnesium primarily in the form of chlorides and sulphates. Salt affected areas an expected to increase with spread of waterlogging and salinity due to increase in canal irrigation, and intensive exploitation of poor quality ground waters for agriculture in non canal commands. Certain states like Rajasthan and Haryana located in the western part of the country are endowed with 84 and 62% of poor quality ground waters, respectively. Continuous use of such waters for irrigation to agricultural crops is bound to increase the problem of salinity and sodicity in India (Yadav 1989; Minhas and Bajwa 2001). Introduction of irrigation without making proper provision for drainage is the major cause for the development of salinity in canal commands.It is severe on irrigated lands of the dry zone. It reduces crop yield and in severe cases causes complete abandonment of agriculture (Joshi and Dhir 1989; Joshi et al. 2000; Mahesh Kumar et al. 2016). The present paper deals with extent, causes, characteristics and management options of these soils for sustainability of agriculture in the area.

Introduction

A number of researchers have used morphological descriptors such as growth habit, leaf, shoot, flower, fruit morphology to classify and discriminate different varieties/cultivars and or detect inter and intra-specific variations in different tree species of economic importance (Saran et al. 2006; Holland et al. 2009). Such morphological descriptors are quite homogenous and often found insufficient to distinguish varieties within morphological groups. The choice of suitable cultivars is of paramount importance for its success. The lack of breakthrough has been due to under utilization of genetic variability for superior quality and high yield potential. Most of the fruit tree species demonstrates a rich genetic diversity mainly through natural cross pollination due to self incompatibility (Godara 1980). The elite plant types with desirable traits have been released as varieties, mass multiplied and propagated through standard vegetative multiplication. However, the authenticity of cultivar identification remains unclear (Devanshi et al. 2007).

Introduction

Rain fed agroecosystem occupies 68% of India’s cultivated area and supports 40% of the human beings and 65% of the livestock population. It produces 44% of food requirements, thus has and will continue to play a critical role in India’s agriculture (Singh et al. 2004). Besides their well established role in agriculture, livestock have crucial role in food security and as risk aversion mechanism for sustaining family, whenever there is crop failure. Indian hot arid zone which is about 12% of total geographical area of the landmass of 0.32 million km2 has maximum covering in western Rajasthan i.e. 61% of the total area whereas the other areas in arid region are available in the states of Gujarat, Punjab, Haryana, Andhra Pradesh and Karnataka accounting for 20, 5, 4, 7 and 3% of hot arid area whereas the cold arid area of 8.4 million ha lies in the state of Jammu & Kashmir covering the Leh and Ladakh region.

Introduction

Throughout the arid zones, there is no dearth of problems, but rapidly increasing desertification (some call it land degradation) is a problem of worldwide dimension. Water is a scare commodity in arid zones. Much of rainfall is lost by evapo-transpiration and as a result, ground water recharged only by seepage through soil profile. However, it is a common phenomenon in arid zones of the world that ground water is frequently used at the rate that exceeds recharge. The situation in arid tropics of India, which is spread over an area of 31.7 million ha, is no more different. Considering the role of agriculture in the social and economic progress of developing countries, the vulnerability of agricultural systems to the impacts of climate change has received considerable attention from the scientific community (Fischer et al. 2002; IISD 2003; Kurukulasuriya and Rosenthal 2003). Much of the available literature suggests that the overall impacts of climate change on agriculture especially in the tropics will be highly negative, although in a few areas there may be minor increases in crop yields in the short term (Maddison et al. 2007). Research on agroforestry as an adaptation to climate change and as a buffer against climate variability is in the process of evolving.

Introduction

Human civilization used to undergo several form of disasters throughout its life history. Most of such events are unpredictable, sudden and short in duration, and such events can easily classifiable as either natural (e.g. cyclones, earth quake, natural forest fires and tsunami) or manmade such as spread of toxic chemicals (e.g. Bhopal disaster 1984), nuclear explosions, civil war, diseases (Minamata, itaiitai, etc.). However, climate change is a real time prolonged disaster which is caused by both natural (caused by variation in solar irradiance, variations in orbital parameters of earth, volcanic activities, natural forest fire, methane release from thawing of permafrost from ocean floor, natural wetlands and cattle) and anthropogenic means (by greenhouse gases resulted from human activities-all kinds of combustion, industrial production of greenhouse gases and agricultural water lodging activities such as paddy cultivation and artificial wet lands, and deforestation).

Introduction

Two types of interactions, i.e. competitive and complementary, are found in ecosystems and agroecosystems (Callaway 1998), which shape community structure, plant diversity and system’s functions (Callaway 1995; Pugnaire et al. 1996; Bruno et al. 2003). Competitive interaction in ecosystems (Wedin and Tilman 1993) and agro-ecosystems (Pandey et al. 1999) is well documented. Mechanism of complementary interaction, however, is not much understood so far. Some studies (Bertness and Callaway 1994; Callaway 1998) argue that complementary interaction is facilitative, either facultative or obligatory, and occur generally in harsh physical environments. This suggests that habitat amelioration by neighbours is a common denominator of positive interactions (Bertness and Callaway 1994; Callaway and Walker 1997). Other studies report that complementary interaction is mutualistic (Boucher et al. 1982). Irrespective of whether facultative or mutualistic, it is now well established that complementary interaction is evolutionary (Bertness and Callaway 1994). But, it is still inconclusive how two species exist together in ecosystems and agroecosystems (Bertness and Callaway 1994).

Introduction

India has a long tradition of agroforestry which is widely practiced in all ecological and geographical regions of the country. Traditional agroforestry systems are broadly based on indigenous knowledge and the species are selected as a part of the cultural patterns of the community. The farmers and land owners in different parts of the country integrate a variety of woody perennials in the crop and livestock production systems depending upon the agro-climatic conditions and local requirements.

Introduction

Arid lands are among the world’s most fragile ecosystems, made more so by periodic droughts and increasing over exploitation of meagre resources. Arid and semi-arid lands cover around one-third of the world’s land area and are inhabited by about one billion people, a large proportion of whom are among the poorest in the world (Malagnoux et al. 2007). Arid environments are extremely diverse in terms of their land forms, soils, fauna, flora, water, and human activities. Aridity is usually expressed as ratio of mean annual precipitation (P) to the mean annual potential evapotranspiration (EPT) where potential evapotranspiration is calculated by method of Penman, taking into account atmospheric humidity, solar radiation, and wind speed. UNEP (1997) has recognized four main classes of aridity: hyper-arid (P/EPT < 0.03), arid (0.03 < P/EPT < 0.20), semi-arid (0.20 < P/EPT < 0.50), and dry sub-humid (0.50 < P/EPT < 0.65). Of the total land area of the world, the hyper-arid zone covers 4.2 %, the arid zone 14.6 %, and the semi-arid zone 12.2 % (FAO 1989). Therefore, almost one-third of the total area of the world is “arid land”. 

Introduction

Agriculture has always been vulnerable to fragile environmental conditions of dry areas, where droughts of varying amplitude and frequency influenced by insufficient and uncertain rainfall are common features. Recent anthropogenic activities have accelerated the rate of green house gas (GHGs) accumulation in atmosphere influencing atmospheric temperature and local patterns of temperature and precipitation, which ultimately affect agricultural production and food securities. About 35.5 percent of the total world’s population resides in dry areas, which is facing the problems of land degradation and food securities.

Introduction

Livestock sector plays an important role in the rural economy at national level and this sector is emerging as a driving force in agriculture by contributing towards the income and employment of rural households. Livestock contributed 16% to the income of small farm households that indicates importance of livestock sector as a whole. In 2010-11, livestock generated outputs worth Rs 2075 billion (at 2004-05 prices). Agriculture sector grew at low rate of 4.7% during 2013-14 and contributed 13.9% to National GDP (Economic Survey 2013-14). The livestock sector contributed over 4.1 per cent of the total GDP in 2012-13, that nearly accounts for 29.5% of the agricultural GDP (Economic Survey 2013-14) indicating a significant contribution of the livestock. Sheep and goats are an important livestock species for a large number of rural poor, especially socially backward, marginal and landless labourers in India. Sheep are mostly reared for wool and meat purpose. India ranks third in sheep population and account for nearly 6% of world sheep population, currently India has 65.06 million sheep as per Livestock census 2012.

Introduction

Arid regions of the world are diverse in terms of climate, soils, vegetation, animals and life style and activities of people. The binding feature of all arid regions in the world is aridity. Of the total area of arid zones of the world, Africa, accounts for 46.1 % followed by Asia (35.5 %). Majority of rest 19.4 % of arid zones are spread over in Australia, North America (Mexico and Southern part of USA), and South America. The Indian arid zone covers around 12 % of country’s geographical area occupying 31.8 million ha of land of which major part is in northwestern India (28.57 Mha) and some in southern India (3.13 Mha). It covers parts of Andhra Pradesh, Gujarat, Haryana, Karnataka, Maharashtra, Punjab and Rajasthan states of India (Table 1 and Fig. 1). The arid regions of Rajasthan, Gujarat, Punjab, and Haryana together constitute Great Indian Desert, better known as Thar. As arid western Rajasthan accounts for 61% of hot arid region of country, therefore it is considered principle hot arid region. Major part of it occurs between Aravalli ranges on the east and southeast and Thal desert of Pakistan (Thal desert is simply the western extension of Thar, only name has been changed) which is spread up to Suleman Kithara ranges in extreme west.

Introduction

Rainfall is the principal source of water in arid areas, which augments soil moisture, groundwater and surface flows. Agriculture and several of the other economic activities in arid areas depend on rain. This region is devoid of any well defined perennial river system. Under such circumstances every drop of water becomes very precious. Of the total water use about 85% of water is used for irrigation and remaining 15% is used for drinking, industrial and other purposes. About 65% of irrigation water and 30-40% of drinking water is subjected to serious losses. Hence, increasing water use efficiency coupled with increasing availability of water through rainwater harvesting and management is of prime importance for sustainable development of arid areas. Rainwater harvesting, its conservation and efficient utilization can solve problem of water scarcity to the greater extend. Rainwater harvesting in small ponds (nadis), underground tanks (tankas), Khadins (Low lying areas) etc. is an age-old tradition in arid zone of Rajasthan. These traditional rainwater harvesting structures vary in design, shape and size. These traditional methods have undergone several changes for being more economical and efficient. Central Arid Zone Research Institute (CAZRI), Jodhpur since its inception in year 1959 is continuously working for development and refinement of water efficient techniques for crop production, individuals and for the communities for development in hot arid zone of India.

Introduction

Agroforestry system (AFS) is a form of sustainable land use that combines trees, shrubs, crops and livestock so as to increase and diversify farm and forest production along with conserving natural resources. Microorganisms play a crucial role in improving nutrient availability to plants, thereby decreasing the dependence on chemical fertilizers and achieve sustainable agriculture through agroforestry (Araujo et al. 2012). Arbuscular mycorrhizal (AM) fungi, plant growth-promoting rhizobacteria (PGPR), and the association of rhizobia with leguminous plants are symbiotic associations of high economic importance for increasing agricultural production. Yadav et al. (2010) studied soil biological properties under different tree based traditional agroforestry systems in a semi-arid region of Rajasthan, India and concluded that biological properties can be optimized in the soil under AFS. Many authors have reported that soil microbial biomass and microbial diversity are greater in the AFS due to the ameliorative effects of trees and organic matter inputs and the differences in litter quality and quantity and root exudates (Mungai et al. 2005; Sørensen and Sessitsch, 2007). Also, the presence of a large and diverse soil microbial community is crucial to the productivity of any agroecosystem. Moreover, more than one plant species in AFS have been reported to have shown a larger diversity and/or abundance of mycorrhizal fungi than monocultures (Cardoso and Kuyper 2006) and more efficiency in biological fixation of the nitrogen, especially in tropical soils (Freitas et al. 2010). Also, soil microbial biomass has other important functions in the soil such as nutrient cycling and the degradation of pollutants (Watanabe and Hamamura 2003; Araújo and Monteiro 2006).

Introduction

Arid environs are delineated by extreme and harsh weather conditions due to excessive heat and inadequate, variable precipitation; however, contrasts in climate occur. These climatic disparities are the result of temperature variation, distribution and season of rainfall and the degree of aridity. Moreover, high evapo-transpiration, periodic droughts, low organic matter levels, different associations of vegetative cover and soil enhances the problems of these regions. In general, hot arid climates have excessive heat and strong prevailing winds, unhampered by obstacles on the ground and as result aeolian erosion is common with frequent seasonal drought occurrence (Sharma and Tewari 2005). These climatic limitations make very difficult place for the inhabitants to attain their livelihood. People of these areas have spent their life within these constraints for centuries. They have faced serious challenges due to lack of sufficient resources and very low productivity which has added to the vulnerability of the region. 

Effect on SOC and N losses through runoff and soil erosion

With increase in population, agriculture is being extended to even marginal soils which were hitherto uncultivated. Such soils are more seriously prone to erosion losses (FAO 2008), mostly because of their topographical position. Overall, soil organic matter and nutrient rich surface soil erosion could become more serious threat in the wake of changing climate in future; therefore, it is necessary to find suitable remedy measures to sustainable food production while protecting the soil from erosion.

Introduction

The rate of increase in anthropogenic CO₂ concentration of the atmosphere is increasing at an alarming rate from 1.7 µmol mol-1 yr-1 in 2009 (Tans 2009) to 2.2 µmol mol-1 yr-1 in 2013 (WMO 2013). At this rate, its level in the atmosphere will reach around 450 µmol mol-1 by the turn of century from its current concentration of 400 µmol mol-1, leading to increased global warming and concomitant climate change. There is, thus, a very strong scientific interest in finding ways to slow or reverse this trend. Mitigation strategy of diverting CO₂ from atmosphere to soil by adopting appropriate agricultural practices such as conservation agriculture (CA) is a recognized such method (Lal 2008 a, b). Broadly, CA has three major components- reduced tillage, crop residue management, and intensive cropping. Conservation tillage practices which include reduced tillage (RT) and no-tillage (NT) have been amply demonstrated as the agricultural practices that are very helpful in this direction (West and Post 2002; Franzluebbers 2010).

Introduction

Tree growing in hot arid region is basically concerned with the management of trees for conservation and for limited production objectives like wood for fuel, poles and fencing material; leaves for livestock fodder; and pod/seeds for many types use in human diet. The role of trees to conserve the fragile ecosystems of hot arid regions has been well recognized (Mann and Muthana 1984). The trees also provided so many services to mankind, which make them an intricate part of man-livestock-agriculture continuum, the lifeline of hot arid regions (Saxena 1997).