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The Coconut palm, also known as the Cocos Nucifera L., is one of the most fascinating and beautiful palms in the world. Epigraphical, literary and sculptural evidence provide proof that coconut has served humanity for more than three millennia. The palm is looked upon with reverence and affection and is referred to by such eulogistic epithets as “Kalpavriksha”, tree of heaven, the tree of abundance, nature’s super market, king of palms and the tree of life. The coconut is believed to have originated in Southeast Asia (Indonesia, Malaysia, Philippines) or Micronesia (Harries, 1977; Purseglove, 1968 and 1972). Coconut has been cultivated in India since ages and plays an important role in social, economic and cultural activities of the people. The palm is amenable to both plantation and homestead management and it can be either a major crop or a minor one in a homestead garden of mixed crops. While responding favourably to scientific management, the palm also tolerates negligent farming to a certain extent. Thus, it can adapt to the divergent farming situations and management practices that are prevalent in different agro-climatic regions. The coconut palm is usually found near the sea on sandy beaches where it can tolerate salt spray and brackish soils. It is also grown under different soil types such as loamy, laterite, coastal sandy, alluvial, clayey and reclaimed soils of the marshy low lands. The ideal soil conditions for better growth and performance of the palm are proper drainage, good water-holding capacity, and presence of water table within three metres and absence of rock or any hard substratum within two meters of the surface. The coconut palm can also grow well inland, within altitudinal limit of 600 m to 1752 m in the Tropics. It requires an equatorial climate with high humidity. A year-round warm and humid climate favours the growth of coconut. The ideal mean annual temperature, which can be tolerated by coconut palm, is around 27ºC with 5–7ºC diurnal variation. The palm does not withstand prolonged spells of extreme weather/climate variations under rainfed conditions. A well-distributed rainfall of 1300–2300 mm per annum is preferred. It is known as a coastal tree since it is grown along the Coasts and Islands and does not tolerate high temperature range, that is the difference between the maximum and minimum temperatures.

Thisprocedure estimates aggregatestabilitytoimpact ofraindropsand water erosion. Wet sieving procedure was originally proposed by Yoder, 1936. Later, the procedure was modified byKemper and Rosenau, 1986.

Equipment

1. Yoder type sieve shaking electrically operated machine (3/4 inch stroke at 30 strokes per minute)
2. Concentric sieves of various sizes of pores to fit properly into the machine.
3. Weighing balance

In dry combustion technique, the combustion of soil sample (about 250 mg and mm sieved) is carried out at high temperature (about 1000 ºC) through feeding in an inert boat in the electric furnace. The CO₂ produced from the oxidation of carbon present in the soil sample at high temperature is carried towards non dispersive infrared detector (NDIR) by a carrier gas where it is quantified and total carbon content is determined.

This is one of the commonly used method to estimate organic carbon content in soil. In this wet digestion method, soil organic matter is oxidised with a mixture of K₂Cr₂O₇ and concentrated H₂SO₄ utilizing the heat of dilution of H₂SO₄. The unused K₂Cr₂O₇ is back titrated with ferrous sulphate or ferrous ammonium sulphate.

Cashew (Anacardium occidentale L.) is a very important horticultural crop which fetches considerable foreign exchange to India. The crop is a native of Brazil and was introduced in India by the Portuguese during 16^th Century. It is grown in India, Brazil, Vietnam, Tanzania, Mozambique, Indonesia, Sri Lanka and other tropical Asian and African countries. The crop is grown within the latitudinal belt of 27°N and 28°S of the equator experiencing a tropical temperature for its growth and development (Rao and Gopakumar, 1994). The trend in productivity has a phenomenal bearing to the distance from the equator. The world production of cashew is estimated to be around 20.8 lakh tonnes. The global productivity level of cashew is 690 kg/ha. Since 2000, the world raw cashewnut production registered an increase of 40 per cent. India’s share in the world raw cashewnut production accounts to about 25 per cent. In recent times, India is facing tight competition from Vietnam and Indonesia in international cashew trade. Since its introduction in the Country, cashew has well adapted to the Indian climatic conditions and is grown in the East and West Coasts of India. Now, India is the largest producer, processor, consumer and exporter of cashew in the world (Bhat, 2009 a). In India, cashew is grown mainly in Maharashtra, Goa, Karnataka and Kerala along the West Coast and Tamil Nadu, Andhra Pradesh, Orissa and West Bengal along the East Coast.

The global production of cocoa is around 36.49 lakh tonnes against the demand of 37.37 lakh tonnes. Ivory Coast leads in cocoa production in the world with a contribution of 38 per cent, followed by Ghana and Indonesia. Unlike in other crops, it appears that the production and demand of cocoa at the global level match each other to a large extent. However, the recent trends in the world production of cocoa beans indicated that there was a drop of nine per cent in 2006–07, declining from 3.8 million tonnes in 2005–06 to 3.4 million tonnes in 2006–07 (Table 9.1). It was attributed to unfavourable conditions in many cocoa producing areas. West Africa, the main cocoa producing region, was hit by a severe harmattan (dusty dry wind from November to March) and its inherent dry weather, which lasted from the end of 2006 to February 2007, had a strong negative impact on global cocoa production. In Asia and South America, El Nino- related weather conditions developed in September 2006 and continued until the beginning of 2007. It led to relatively low cocoa production in 2007–07. However, it was rebounced in 2007– 08 to some extent though it was low (36.49 lakh tonnes) when compared to that of 2005–06. The favourable weather which prevailed over most of the cocoa growing regions during 2002–03 and 2003–04 helped to achieve better production during the above years while dip in the global production in 2006–07 due to unfavourable weather. It reveals that the weather abnormalities like floods, droughts, cold and heat waves across the cocoa growing regions of the world adversely affect the Coca production and the cocoa industry is likely to suffer.

Small cardamom (Elettaria cardamomum Maton), popularly known as the “Queen of spices”, occupies an important position among the foreign exchange earning commodities. Cardamom is cultivated on a commercial scale in Sri Lanka, Guatemala, Tanzania and Papua New Guinea. Guatemala is the largest producer of cardamom in the World. In India, it is confined to the States of Kerala, Karnataka and Tamil Nadu, accounting for an area of 41588 ha, 25021 ha and 4561 ha, respectively (Spices Board, 2009). Among these States, Kerala accounts for the major portion of production (58.4 %), followed by Karnataka (35.2 %) and Tamil Nadu (6.4 %). In Kerala, Cardamom is mainly grown in the erstwhile Travancore area in the present Idukki district and it is known as the Cardamom Hill Reserve (CHR), which was specially reserved, denotified and removed from the control of forest development by the orders of the Travancore Government. By a Royal Proclamation in Medam 997(ME) 334 square miles (86,506 ha) area in Devikulam, Udumbanchola and Peermedu taluks of the present Idukki District was declared as CHR for the promotion of cardamom cultivation (Miniraj and Nybe, 2007). Cardamom is a native of the moist evergreen rain forests of the Western Ghats of South India and is grown extensively in the hilly regions at elevations of 700 to 1300 metres as an under crop in forest lands. Cardamom thrives well within certain thermal regimes. It is believed that diurnal symmetries in temperature trends, if any, have close links with the changes in cloudiness, humidity, atmospheric circulation pattern, winds and soil moisture (Kumar et al., 2002).

Labile fractions of soil carbon (C) refer to the fraction of soil carbon that are easily altered by microbial activities. These fractions serve as sensitive indicators to changes in management induced soil quality and are grouped under active soil C pool. The method described by Weil et al. (2003)estimates changes in biologically active soil C using a dilute KMnO . This is an improvement over the method used by Blair et al (1995), where a very high concentration (0.333 M) of KMnO₄ was used.

Organic carbon present in soil can be very labile, labile or non-labile. This procedure measures the extent of lability of soil organic carbon through relative degree of oxidation by K₂Cr₂O₇.

Particulate soil organic matter (POM) is one of the important soil organic matter (SOM) pools and matches the characteristics of a slow, decomposable or stabilized SOM pool. The POM fraction is considered as one of the indicators to changes in management and thus has been used in soil quality assessment studies.

The natural habitat of rubber (Heavea brasiliensis) is rain forests of the Amazon basin, situated within 5° North and South at altitudes below 200m. The climate of this region is equatorial monsoon type characterized by mean monthly temperature by 25 to 28°C, well distributed rainfall and no marked dry weather. Though it is originated in the Amazon basin, it is now predominantly grown in the tropics where an equatorial monsoon type climate prevails. Regions between 8°N and 10°S which includes Indonesian archipelago, Malaysia, southern part of Sri Lanka and some other Islands, are better suited to rubber cultivation. The production of natural rubber in the country was 8.65 lakh MT in 2008–09, registering a 4.74 per cent growth compared to the previous year.

Black pepper (Piper nigrum L.), famous as “Black Gold” and also known the “King of Spices” is the most important agricultural commodities of commerce and trade in India. It is the most important, most popular and most widely used spice in the World. Of the total spices traded internationally, black pepper accounts for 34 per cent. South West India is the traditional home of this important spice, particularly the Malabar Coast. Black pepper is also grown in tropical zones such as the Asia Pacific Region, mainly India, Indonesia, Malaysia, Sri Lanka, Thailand, China, Vietnam and Cambodia. Outside the Asia Pacific region, the crop is distributed in Brazil, Mexico, Guatemala, etc., totaling about 26 countries. It is grown successfully between 20°N and 20°S latitude and from mean sea level to 1500 meters above sea level. World’s black pepper production varies in the range of 2.7 to 3.35 tonnes annually.

The State of Kerala under the Humid Tropics is one of the wettest places in the Humid Tropics where annual rainfall is of the order of 3000 mm, ranging from less than 1000 mm to greater than 5000 mm. About 68 per cent of the rainfall is obtained during southwest monsoon while 16 per cent in post monsoon and the rest from summer (14 per cent) and winter rainfall (2 per cent). Bi-model rainfall pattern is noticed towards southern districts due to influence of both southwest and northeast monsoons while uni-model rainfall pattern towards northern districts of Kerala. Coconut productivity is better towards south despite dreaded disease of root-wilt when compared to that of northern districts due to less dryspells during summer. Floods during monsoon adversely affect paddy production in the State while prolonged droughts during summer in the absence of post monsoon rainfall adversely affect plantation crops’ production to a considerable extent. The wetlands in Kerala are rich sources of water during summer and act as sink during monsoon season. Such wetlands are fast declining in Kerala and converted as garden lands. Decreasing wetlands might be one of the reasons for frequent floods and droughts in Kerala in recent years. The forest cover of Kerala also declined from 70 per cent to 24 per cent over a period of one- hundred- and - fifty years due to deforestation and forest fires.

Coffee is grown at higher elevation across the Western Ghats between 750 and 1200 m amsl. It requires a certain degree of shade for its better performance. The annual rainfall over the coffee growing tracts varies between 1400 and 2600mm, having uni/bi-model rainfall with prolonged dryspell from November to May. It is more so over North of the Western Ghats. The mean annual maximum temperature varies between 24 and 30⁰C while the minimum between 15 and 18⁰C. The difference between maximum and minimum temperatures (temperature range) varies between 5 and 16⁰C across the coffee tract. The ‘Monsooned Malabar Coffee’ is a specialty coffee produced from the erstwhile ‘Malabar Region’. It undergoes certain changes in physical and biochemical characters when the coffee beans are processed during the summer monsoon (June to September). It is processed at Mangalore, located in Coastal Karnataka. The processing location experiences heavy rainfall of more than 1000 mm in July, followed by 950 mm in June and 600 mm in August. Out of 3264 mm of annual rainfall, 2852 mm is received during the monsoon period. It accounts more than 80 per cent of annual rainfall. The maximum temperature during the monsooning varies between 28 and 30°C while night temperature revolves between 22 and 24°C. Being located in the tropics along the West Coast, the crop processing environment in terms of surface air temperature is relatively uniform and moderate with a characteristic feature of heavy clouds and continuous rainfall during the monsoon period.

Soil respiration is a good estimator of overall biological activity and thus is often used for describing soil quality. Soil respiration is estimated as the flux of CO₂ emitted from the soil surface. It represents the sum of CO₂ produced by root respiration and by heterotrophic decomposition. This procedure is a laboratory method where soil is incubated for a given period of days and the released CO is trapped by sodiumhydroxide (NaoH). This is also known as alkali trap method.

This is a distillation method proposed by Subbiah and Asija (1956), where the soil is distilled with alkaline KMnO solution. The ammonia liberated is trapped in boric acid and then determined by titration against a standard acid. This procedure estimates the easily mineralizable nitrogen in soil.

Estimation of plant available phosphorus content in soil has been attempted using several extractants. However, Bray’s reagent and Olsen’s reagent are the two common extractants used in India. Bray’s reagent (0.03 N NH₄F and N HCl) is used for acid soils, where, the fluoride ion complexes with Fe and Al in soil and thus releases the bound P. The Olsen’s reagent (0.5 M NaHCO₃) is used for neutral-alkaline soils.

The global economy has adversely been affected to a considerable extent due to weather related disasters which are not uncommon in the recent past due to global warming and climate change. It is true in the case of the Indian economy too. The year 2010 was the warmest year ever recorded, followed by 2009 in India. The year 2015 was the warmest year globally. Model simulations indicate that a marked increase in rainfall and temperature over India would be seen during the current century. The maximum expected increase in rainfall is likely to be 10–30% over the Central India. Temperatures are likely to increase between 2 and 3^oC by the end of 2100 A.D. Greater number of high surges and increased occurrence of cyclones in post monsoon period along with increased maximum wind speed are also expected along the East Coast of the Country. As a result, the occurrence of floods and droughts, cold and heat waves adversely affected the foodgrains production to a large extent across the Country in one or other region as seen in 2014, 2012, 2009, 2004, 2002 and 1987. It is true in the case of plantation crops also, which are predominantly grown in the Humid Tropics like Kerala (8°15` N and 12°50`N latitudes and between 74°50`E and 77°30`E longitudes). As seen in previous chapters, summer drought and heavy rains including waterlogging during monsoon period is a threat to plantation crops production in the Humid Tropics to a considerable extent. Waterlogging and floods due to excess rains could be minimised by providing surface and subsurface drainage facilities in plantation gardens which will improve the soil health and nutritional status, in turn yields can be increased in plantation crops.

Climate change impacts on agriculture are being witnessed all over the world, but countries like India are more vulnerable in view of the high population that depends on agriculture and excessive pressure on natural resources. The warming trend in India over the past 100 years (1901 to 2007) was observed to be 0.51°C with accelerated warming of 0.21oC per every 10 years since 1970 (Kumar, 2009). The projected impacts are likely to further aggravate the yield fluctuations of many crops with impact on food security and prices. Climate change impacts are likely to vary in different parts of the country. Parts of western Rajasthan, Southern Gujarat, Madhya Pradesh, Maharashtra, Northern Karnataka, Northern Andhra Pradesh and Southern Bihar are likely to be more vulnerable in terms of extreme events (Mall et al., 2006).

The green revolution enhanced the food grain production by increasing  productivity of the arable crops as the only means of expanding output. The impact of this ‘revolution’ was first realized especially in the north Indian states of Punjab, Haryana, and western Uttar Pradesh. Since the new technology was based on use of seeds of high yielding varieties, increased use of irrigation and chemical fertilizers, pesticides and farm mechanization; the incremental gains in productivity of late began to end and food production started stagnating, and in many places it even acquired a decreasing trend. It is well accepted fact that ‘success always has its costs and green revolution has been no exception’. Critics of green revolution point to the environmental and health hazards due to increased use of agro-chemicals and the vulnerabilities that is there due to the spread of monocultures in which indigenous land races have been ignored and least emphasis was given on cropping systems based on crop diversification.