**3. Forage legumes in soil health and ecosystem services**

Forage legumes is essential for providing a source of biological nitrogen fixation (BNF) for enriching soil fertility (15–40 kg fixed N/ha), reduction in land degradation, disease breaks and for mitigating climate change. Estimating biological N2 fixation of the forage and fodder legumes precisely is challenging because statistics on the areas and productivity of these legumes are highly difficult to obtain. Therefore, N<sup>2</sup> fixation values of forage and fodder legumes will be less reliable and also estimates of %Ndfa (nitrogen derived from atmosphere) of fodder legumes in those lands. There are very few reports available on forage legumes—BNF in India. But, all works mainly focused on application of *Rhizobium* inoculants to fodder legumes and testing their potential for enhancing fodder production (fresh and dry weight, crude protein content, forage quality aspects, nodulation properties, etc.). Appreciable amount of atmospheric N (~60–100%) is fixed by forage legumes annually, fixing up to 380 kg N ha−<sup>1</sup> [5]. Quantity of forage residues available for soil incorporation range from 80 to 143 kg N ha−<sup>1</sup> and rice cultivated following forage legumes yields the same as rice with 24–50 kg fertilizer N ha−<sup>1</sup> [6]. About 100–120 Mha of land is under fodder and forage legumes and green manure crops, with assumed average N2 fixation rates of 200 kg N/ha/year for alfalfa, 150 kg N/ha/year for clovers (*Trifolium* spp.), 100 kg N/ha/year for other forages and 50 kg N/ha/year for legume-grass pastures [7]. From this assumption, total nitrogen fixation by forage and fodder legumes was calculated at 12 Tg annually (average of about 110 kg N/ha/year). But fixation by legume-grass mixtures is much more variable, ranging from a just a few kilograms to more than 250 kg N ha−<sup>1</sup> .

classification, evolution and origin. Therefore, maintenance of enormous genetic diversity is mandatory for broadening the genetic base of the present and future forage improvement programmes to achieve the national goals. Extensive collection, proper evaluation, in depth study of genetic attributes and cataloging of germplasm is prerequisite for its efficient utilization. According to an estimate there are about 650 genera, 18,000 species of legumes (Leguminosae) in the world. Out of these, only about 30 legumes are used to an appreciable extent for forage production [15]. Information regarding the centre of origin of different

Tropical Forage Legumes in India: Status and Scope for Sustaining Livestock Production

http://dx.doi.org/10.5772/intechopen.81186

127

World-wide, 1500 gene banks are registered in the WIEWS (World Information and Early Warning System on PGR) database [16] and conserve a total of 7.1 million accessions belonging to 53,109 species, including major crops, minor or neglected crop species, as well as trees and wild plants. Out of total germplasms stored, 651,024 accessions belonging to forage

*Centrosema pubescens* South America South east Asia, Indonesia and Africa *Clitoria ternatea* Tropical America Tropical and subtropical parts of the world

Throughout the tropical areas of Africa,

Australia, South east Asia, Pacific Islands

Australia and new world

Tropical parts of world

*Desmanthus virgatus* Argentina Florida, throughout the India

America

America

*Macroptilium lathyroides* India Tropical and subtropical world

Venezuela

*Stylosanthes scabra* Tropical America Kenya, Brazil and Queensland

*Cyamopsis tetragonoloba* Africa India (secondary centre of origin)

*Medicago sativa* Asia Minor Near East and central Asia

*Stylosanthes guianensis* Brazil West Indies, Africa and Pacific Islands *Stylosanthes hamata* Islands of West Indies Coastal regions of north and south America

*Lablab purpureus* Asia or Africa India, subtropical areas of Africa, south Asia

**Genus Species Centre of origin Distribution**

*Macrotyloma* spp. Africa and Asia Sri Lanka *Macrotyloma uniflorum* India Africa

forage crops is furnished in **Table 1**.

*Atylosia scarabaeoides* India

*Desmodium intortum* Central and South

*Macroptilium atropurpureum* Central and South

*Stylosanthes humilis* North east Brazil and

*Trifolium alexandrinum* Syria Egypt

*Stylosanthes seabrana* Brazil

**Table 1.** Centre of origin of different tropical forage legumes.

In India, area under fodder legumes and grasses is about 8 Mha (*Sorghum bicolor*—2.6 Mha, *Trifolium*—1.9 Mha, *Medicago*—1 Mha, other legume forages—1.9 Mha). Mean N uptake by *Trifolium alexandrinum* (240–264 kg/ha), *Medicago sativa* (216–264 kg/ha), *Vigna unguiculata* (161–181 kg/ha), *Sorghum bicolor* (128–160 kg/ha), BN hybrid (*Pennisetum glaucum* × *Pennisetum purpureum*) and *Megathyrsus maximus* (288–360 kg/ha), *Avena sativa* (120–144 kg/ha). Percent nitrogen derived from atmosphere (%Ndfa) is about 0.7 for legumes and 0.1 for cereals/ grasses. Annual contribution of BNF by forage and fodder crops in India is about 0.61 Tg/year which is nearly 5% of world BNF of forage and fodder [8]. However, majority of values available for legume N2 fixation were based on shoots and above ground parts only. They did not include the fixed N present in roots, nodules and rhizodeposition in general. Published values for below-ground N as a percentage of the total plant N are 22–68% for the pulse and oilseed legumes, *Glycine max*, *Vicia faba*, *Cicer arietinum*, *Vigna radiata*, *Lupinus albus*, *Pisum sativum* and *Cajanus cajan* and 34–68% for the pasture/fodder legumes, subterranean clover, white clover and alfalfa [9–11].

In addition to BNF, many forage legumes have soil-covering growth habit similar to most grasses and deep root system which can contribute to the mitigation of many soil problems, *viz*., soil conservation by legume cover crops such as *Stylosanthes*, *Crotalaria*, *Sesbania*, *Arachis* and *Desmodium* to prevent erosion; contour-hedges with leguminous trees such as *Leucaena*; rehabilitation of degraded soils by legumes such as *Stylosanthes* spp., which are deep-rooted and adapted to infertile soils, cycle minerals from deeper soil layers resulting in soil improvement and enhanced concentration of soil organic matter through litter production [12]; the potential of legumes like *Stylosanthes hamata* can be exploited to ameliorate compacted soil [13]. When used as cover crop forage legumes can also control weed growth, which can be exploited as an attractive alternative to the use of herbicides. They supplement part of N fertilizer application, thus reduce nitrate leaching and eutrophication of water bodies as a consequence of surface runoff as a result of N fertilization in tropical pasture production process. Tropical forage legumes have considerable potential to increase productivity of forage-based livestock systems, while providing benefits to the environment [14]. The environmental benefits, referred as 'ecosystem services', comprise positive effects on: soil conservation and soil chemical, physical and biological properties; mitigation of global warming and of groundwater contamination; saving of fossil energy; and rehabilitation of degraded lands [14]. These features make tropical forage legumes particularly valuable at all levels of the system because of their interaction with plants, soil, animals and the atmosphere.

## **4. Genetic resources of tropical forage legumes**

Plant genetic resources (PGR) are the basic platform for screening, improving and developing fine cultivars, and the important materials for biodiversity studies including classification, evolution and origin. Therefore, maintenance of enormous genetic diversity is mandatory for broadening the genetic base of the present and future forage improvement programmes to achieve the national goals. Extensive collection, proper evaluation, in depth study of genetic attributes and cataloging of germplasm is prerequisite for its efficient utilization. According to an estimate there are about 650 genera, 18,000 species of legumes (Leguminosae) in the world. Out of these, only about 30 legumes are used to an appreciable extent for forage production [15]. Information regarding the centre of origin of different forage crops is furnished in **Table 1**.

assumption, total nitrogen fixation by forage and fodder legumes was calculated at 12 Tg annually (average of about 110 kg N/ha/year). But fixation by legume-grass mixtures is much more

In India, area under fodder legumes and grasses is about 8 Mha (*Sorghum bicolor*—2.6 Mha, *Trifolium*—1.9 Mha, *Medicago*—1 Mha, other legume forages—1.9 Mha). Mean N uptake by *Trifolium alexandrinum* (240–264 kg/ha), *Medicago sativa* (216–264 kg/ha), *Vigna unguiculata* (161–181 kg/ha), *Sorghum bicolor* (128–160 kg/ha), BN hybrid (*Pennisetum glaucum* × *Pennisetum purpureum*) and *Megathyrsus maximus* (288–360 kg/ha), *Avena sativa* (120–144 kg/ha). Percent nitrogen derived from atmosphere (%Ndfa) is about 0.7 for legumes and 0.1 for cereals/ grasses. Annual contribution of BNF by forage and fodder crops in India is about 0.61 Tg/year which is nearly 5% of world BNF of forage and fodder [8]. However, majority of values avail-

include the fixed N present in roots, nodules and rhizodeposition in general. Published values for below-ground N as a percentage of the total plant N are 22–68% for the pulse and oilseed legumes, *Glycine max*, *Vicia faba*, *Cicer arietinum*, *Vigna radiata*, *Lupinus albus*, *Pisum sativum* and *Cajanus cajan* and 34–68% for the pasture/fodder legumes, subterranean clover, white clover

In addition to BNF, many forage legumes have soil-covering growth habit similar to most grasses and deep root system which can contribute to the mitigation of many soil problems, *viz*., soil conservation by legume cover crops such as *Stylosanthes*, *Crotalaria*, *Sesbania*, *Arachis* and *Desmodium* to prevent erosion; contour-hedges with leguminous trees such as *Leucaena*; rehabilitation of degraded soils by legumes such as *Stylosanthes* spp., which are deep-rooted and adapted to infertile soils, cycle minerals from deeper soil layers resulting in soil improvement and enhanced concentration of soil organic matter through litter production [12]; the potential of legumes like *Stylosanthes hamata* can be exploited to ameliorate compacted soil [13]. When used as cover crop forage legumes can also control weed growth, which can be exploited as an attractive alternative to the use of herbicides. They supplement part of N fertilizer application, thus reduce nitrate leaching and eutrophication of water bodies as a consequence of surface runoff as a result of N fertilization in tropical pasture production process. Tropical forage legumes have considerable potential to increase productivity of forage-based livestock systems, while providing benefits to the environment [14]. The environmental benefits, referred as 'ecosystem services', comprise positive effects on: soil conservation and soil chemical, physical and biological properties; mitigation of global warming and of groundwater contamination; saving of fossil energy; and rehabilitation of degraded lands [14]. These features make tropical forage legumes particularly valuable at all levels of the system because

Plant genetic resources (PGR) are the basic platform for screening, improving and developing fine cultivars, and the important materials for biodiversity studies including

fixation were based on shoots and above ground parts only. They did not

.

variable, ranging from a just a few kilograms to more than 250 kg N ha−<sup>1</sup>

of their interaction with plants, soil, animals and the atmosphere.

**4. Genetic resources of tropical forage legumes**

able for legume N2

126 Forage Groups

and alfalfa [9–11].

World-wide, 1500 gene banks are registered in the WIEWS (World Information and Early Warning System on PGR) database [16] and conserve a total of 7.1 million accessions belonging to 53,109 species, including major crops, minor or neglected crop species, as well as trees and wild plants. Out of total germplasms stored, 651,024 accessions belonging to forage


**Table 1.** Centre of origin of different tropical forage legumes.

crops [17]. Among the international organizations major forage germplasm repositories are International Livestock Research Institute (ILRI), Nairobi, CIAT Columbia; ICARDA Syria; CSIRO-Australia, IGER-UK, USDA-Fort Collins. Forage germplasm diversity in these organizations is part of a Consultative Group of International Agricultural Research (CGIAR) coordinated activity in plant genetic resources. The ILRI Gene bank conserves more than 18 thousand accessions of forages from over 1000 species. This is one of the most diverse collections of forage grasses, legumes and fodder tree species held in any gene bank in the world [18]. CIAT gene bank keeps 35,898 accessions of beans, for 44 species of the genus *Phaseolus* from 109 countries, and 23,139 forage accessions belonging to 668 different species of grasses and legumes from 72 countries, that have been introduced over the past 30 years [19]. The IITA gene bank holds the world's largest and most diverse collection of cowpeas, with 15,122 unique samples from 88 countries, representing 70% of African cultivars and nearly half of the global diversity.

**S. no.** **Agro climatic zone/regions**

Hills

1 Western Himalayan Region

2 Eastern Himalayan Region

3 Lower Gangetic Plains

4 Middle Gangetic Plains

5 Upper Gangetic Plains

6 Trans-Gangetic Plains

7 Eastern Plateau and Hills

8 Central Plateau Hills

9 Western Plateau and Hills

10 Southern Plateau and Hills

11 East Coast Plains and Hills

12 West Coast Plains and Hills

13 Gujarat Plains and Hills

14 Western Dry Region

Adopted from Singh et al. [77].

**Subzones/sub regions Prominent forage genetic resources**

Tropical Forage Legumes in India: Status and Scope for Sustaining Livestock Production

*Medicago* spp., *Arundinella nepalensis*, Chrysopogon, *Dactylis glomerata*, *Eleusine*, *Echinochloa*, *Festuca*, *Zea* 

129

http://dx.doi.org/10.5772/intechopen.81186

Rice bean, maize, range grasses, *Brachiaria*, broom grass and lablab

Rice bean, guinea grass, coix and

Maize, sorghum, cowpea Senji, *Dichanthium*, sehima and *Heteropogon*

Cowpea, rice bean, *Pennisetum pedicellatum*, guinea grass, *Dichanthium* spp. and *Atylosia*

Maize, cowpea, rice bean, *P. pedicellatum*, *Coix*, *Atylosia*, sorghum, bajra, guar, *Cenchrus*, range grasses and legumes

small millet, *Heteropogon*, *Dichanthium* sehima and *Stylosanthes* sp*.*

Maize, sorghum, *Dichanthium spp.* pearl millet, *Dichanthium carzacosum*, *Vicia*, cowpea, rice bean, Cenchrus, range grasses and legumes

cowpea, rice bean, guinea grass, coix, small millet, sorghum, *Heteropogon*, *Dichanthium* and *Stylosanthes* sp.

Congo, signal grass, *Paspalum*, *panicum*, *Digitaria*, *Brachiaria*, *Iseilema laxum*, *Isilemia* and *Vicia*

pearl millet, chioori, range grasses

and legumes

millet and *Cenchrus* spp.

Maize, cowpea, rice bean, *Pennisetum* 

Guar, maize, bajra, berseem, lucerne, guinea grass, sorghum and cowpea

*mays*, Kikui *grass*

range grasses

*pedicellatum* and coix.

bean

Jammu & Kashmir, Himachal Pradesh, Uttarakhand

Sikkim, Arunachal Pradesh, Meghalaya, Nagaland, Manipur, Tripura, Mizoram, Assam, Jalpaiguri and

Basin plains, central alluvial plains, alluvial coastal

12 districts of eastern Uttar Pradesh and 27 districts

central, south-western and northern-western Uttar

Punjab, Haryana, Delhi, Chandigarh and Sri

(i) Sub region of Wainganga, Madhya Pradesh, eastern hills and Orissa inland; (ii)Orissa northern, Madhya Pradesh, eastern hills and plateau; (iii) north and eastern Chota Nagpur hills and plateau; (iv) Chota Nagpur south, West Bengal hills and plateau, and (v) Chhattisgarh and south-western Orissa hills.

46 districts of Uttar Pradesh, Madhya Pradesh and

Maharashtra, parts of Madhya Pradesh and one

35 districts of Andhra Pradesh, Karnataka and Tamil

(i) Coastal Orissa (ii) North-Coastal Gujarat (iii) South-Coastal Andhra Pradesh, North-Coastal Tamil Nadu (v) Thanjavur and (vi) South Coastal Tamil

Western coast of Tamil Nadu, Kerala, Karnataka,

**Table 2.** List of prominent forage genetic resources distributed in 15 agro climatic zones of India.

19 districts of Gujarat Lucerne, sorghum, small millet,

Nine districts of Rajasthan Guar, moth, cowpea, sorghum, pearl

Ganganagar district of Rajasthan

Cooch Bihar district of West Bengal

plains and *Rarh* plains

of Bihar plains

Pradesh

Rajasthan

Nadu

Nadu.

district of Rajasthan

Maharashtra and Goa

15 Island Region Territories of the Andaman and Nicobar Islands and

Lakshadweep

Indian sub-continent being one of the world's mega centres of crop origin and crop plant diversity, represents a wide spectrum of eco-climate and reported diversity of 21 forage legumes genera *viz*., *Desmodium*, *Lablab*, *Stylosanthes*, *Vigna*, *Macroptelium*, *Centrosema* and browse plants including *Leucaena*, *Sesbania*, *Albizia*, *Bauhinia*, *Cassia*, *Grewia*, etc. (**Table 2**). Diversity of cultivated and range legumes were collected in form of 3261 diverse germplasm accessions through different indigenous and exotic germplasm collection programme. Collected diversity of forage legumes were evaluated and sources for different biotic and abiotic stress tolerance were identified apart from >50 cultivars in different forage legumes for different geographic regions developed. Crop wild relatives (CWR) being the reservoirs of genes for stress tolerance and quality have been utilized for genetic enhancement of forage legumes. The main centre of diversity for tropical legumes *viz*., *Dolichos*, *Desmodium*, *Vigna* and *Crotalaria* is peninsular India and subtropical legumes *viz*. *Teramnus*, *Atylosia*, *Pueraria* and *Mucuna* are mainly confined to north eastern region. Likewise, rich genetic wealth for the temperate legumes namely *Medicago*, *Melilotus*, *Trifolium* and *Hedysarum* is distributed in western Himalayan region [20]. Besides, India possesses enormous diversity of minor and under-utilized fodder species such as *Agrostis alba*, *Desmodium parvifolium*, *Leptochloa fusca*, *Potentilla fruticosa*, *Rhynchosia minima* and *Salvadora persica* [21]. The forage genetic wealth of India distributed in 15 agro-climatic zones has been summarized in **Table 2**.

The National Bureau of Plant Genetic Resources (NBPGR) is the nodal agency for characterization, evaluation, maintenance, conservation, documentation and distribution of germplasm resources in India. Currently a total of 4594 accessions of different forage crops including cereal forages (1167), grasses (11,160, range legumes (1443), forage millets (781) and others [85] are being maintained at long term storage (LTS) module of National Gene Bank at NBPGR, New Delhi [22]. Indian Grassland and Fodder Research Institute (IGFRI) is a unique R&D organization in South Asia for sustainable agriculture through quality forage production for improved animal productivity. IGFRI being the National Active Germplasm Sites (NAGS) on forages works with its three regional stations and All India Coordinated Research Project (AICRP) on forage crops with 18 coordinated centres. At present IGFRI maintains more than 8000 accessions of 19 major forage crops including cereal forages, forage legumes, grasses and fodder tree at midterm storage [23].


crops [17]. Among the international organizations major forage germplasm repositories are International Livestock Research Institute (ILRI), Nairobi, CIAT Columbia; ICARDA Syria; CSIRO-Australia, IGER-UK, USDA-Fort Collins. Forage germplasm diversity in these organizations is part of a Consultative Group of International Agricultural Research (CGIAR) coordinated activity in plant genetic resources. The ILRI Gene bank conserves more than 18 thousand accessions of forages from over 1000 species. This is one of the most diverse collections of forage grasses, legumes and fodder tree species held in any gene bank in the world [18]. CIAT gene bank keeps 35,898 accessions of beans, for 44 species of the genus *Phaseolus* from 109 countries, and 23,139 forage accessions belonging to 668 different species of grasses and legumes from 72 countries, that have been introduced over the past 30 years [19]. The IITA gene bank holds the world's largest and most diverse collection of cowpeas, with 15,122 unique samples from 88 countries, representing 70% of African cultivars and nearly half of

Indian sub-continent being one of the world's mega centres of crop origin and crop plant diversity, represents a wide spectrum of eco-climate and reported diversity of 21 forage legumes genera *viz*., *Desmodium*, *Lablab*, *Stylosanthes*, *Vigna*, *Macroptelium*, *Centrosema* and browse plants including *Leucaena*, *Sesbania*, *Albizia*, *Bauhinia*, *Cassia*, *Grewia*, etc. (**Table 2**). Diversity of cultivated and range legumes were collected in form of 3261 diverse germplasm accessions through different indigenous and exotic germplasm collection programme. Collected diversity of forage legumes were evaluated and sources for different biotic and abiotic stress tolerance were identified apart from >50 cultivars in different forage legumes for different geographic regions developed. Crop wild relatives (CWR) being the reservoirs of genes for stress tolerance and quality have been utilized for genetic enhancement of forage legumes. The main centre of diversity for tropical legumes *viz*., *Dolichos*, *Desmodium*, *Vigna* and *Crotalaria* is peninsular India and subtropical legumes *viz*. *Teramnus*, *Atylosia*, *Pueraria* and *Mucuna* are mainly confined to north eastern region. Likewise, rich genetic wealth for the temperate legumes namely *Medicago*, *Melilotus*, *Trifolium* and *Hedysarum* is distributed in western Himalayan region [20]. Besides, India possesses enormous diversity of minor and under-utilized fodder species such as *Agrostis alba*, *Desmodium parvifolium*, *Leptochloa fusca*, *Potentilla fruticosa*, *Rhynchosia minima* and *Salvadora persica* [21]. The forage genetic wealth of India distributed in 15 agro-climatic zones has been summarized in

The National Bureau of Plant Genetic Resources (NBPGR) is the nodal agency for characterization, evaluation, maintenance, conservation, documentation and distribution of germplasm resources in India. Currently a total of 4594 accessions of different forage crops including cereal forages (1167), grasses (11,160, range legumes (1443), forage millets (781) and others [85] are being maintained at long term storage (LTS) module of National Gene Bank at NBPGR, New Delhi [22]. Indian Grassland and Fodder Research Institute (IGFRI) is a unique R&D organization in South Asia for sustainable agriculture through quality forage production for improved animal productivity. IGFRI being the National Active Germplasm Sites (NAGS) on forages works with its three regional stations and All India Coordinated Research Project (AICRP) on forage crops with 18 coordinated centres. At present IGFRI maintains more than 8000 accessions of 19 major forage crops including cereal forages, forage legumes,

the global diversity.

128 Forage Groups

**Table 2**.

grasses and fodder tree at midterm storage [23].

**Table 2.** List of prominent forage genetic resources distributed in 15 agro climatic zones of India.
