**9. Frankia with actinorrhizal plants**

*Sustainable Crop Production*

**280**

**Name of the** 

**Azospirillum/Azotobater**

**Frankia/Rhizobium**

**Phosphate solubilizing** 

**AM fungi**

**Combination of** 

**Reference**

**bio-fertilizers**

**bacteria**

**species**

**CD**

*Casuarina* 

14.2

55

19.6

17.6

23

23

6.8

406

11

18

19.5

23

63.5

62.2

115.0

[22]

*equisetifolia* L.

*Acacia nilotica* L.

*Azadirachta indica*

1.1

2.34

3.2

NA

NA

NA

NA

5.5

3.74

0.7

7.08

5.4

0.67

16.0

7.49

[27]

(A) Juss

*Moringa oleifera* L.

*Mangifera indica*

12.0/13.3

12.7/

—

NA

NA

NA

NA

NA

NA

14.73

14.5

NA

11.8

12.9

NA

[117]

13.7

(L.) Delile

*Delonix regia*

5.8/4.2

5.2/

17.8/5.8

NA

NA

NA

NA

NA

NA

3.5

2.42

0.9

13.0

7.9

21.2

[28]

4.3

(Hook.) Raf.

*Tectona grandis*

−−/69.8

−−/

−−/28.2

NA

NA

NA

31.7

0.65

106.8

6.3

7.2

37.4

114.3

26.8

258.9

[116]

0.65

L.f.

*Samanea* 

60.0

20.6

35.8

NA

NA

NA

54.4

6.68

19.5

78.9

16.9

30.9

108.6

46.9

74.9

[67]

*saman*(Jacq.)

Merr.

*Feronia* 

71.4

39.5

55.5

NA

NA

NA

48.8

6.68

15.9

82.9

20.7

41.7

122.8

47.0

92.4

[30]

*elephantum* L.

*Gmelina arborea*

11.6 *CD, collar diameter; SL, shoot length; BM, biomass; NA, not applicable.*

*Growth and biomass increases (percentage increased over control) of horticulture and forestry crops treated with bio-inoculants.*

13.9

38.8

NA

NA

NA

11.9

8.8

27.5

11.9

9.43

63.4

25.6

21.9

166.4

[118]

(Roxb.)

**Table 1.**

75

22

276

NA

NA

NA

5.04

6

17

NA

NA

NA

5.6

11.7

176.5

[25]

61.0

60

26

125

57

56

NA

NA

NA

96

60

48

236.3

131.2

156.8

[26]

**SL**

**BM**

**CD**

**SL**

**BM**

**CD**

**SL**

**BM**

**CD**

**SL**

**BM**

**CD**

**SL**

**BM**

Frankia is a genus of Actinomycetes, belongs to family Frankiaceae and an ability to fix the atmospheric nitrogen in symbiotic association with *Casuarina* species in tropical and temperate environmental condition. These microorganisms usually invade root hairs of Casuarina and developing within cortical cells in lobes of the resultant nodules. Frankia are able to convert the nitrogen gas in the atmosphere into amino acids, which are the building blocks of proteins. Frankia exchange nitrogen for carbohydrates from the plant. As the plant drop organic matter, or when the plants die, the nitrogen from their tissues is made available to other plants and organisms. This process of accumulating atmospheric nitrogen in plants and recycling it through organic matter is the major source of nitrogen in tropical ecosystems. Various agroforestry practices such as alley cropping, improved fallow, and green manure/cover cropping exploit this natural fertility process by using nitrogen fixing plants.

*Casuarina equisetifolia* seedling inoculated with Frankia strains showed improved growth, biomass and tissue N content over control seedlings [24, 111, 112]. Nitrogenase activity of Frankia strains were significantly (*p* < 0.05) and negatively correlated with a tissue N content [111]. Similarly, under nursery experiments, the growth and biomass of *C. equisetifolia* rooted stem cuttings inoculated with Frankia showed three times higher growth and biomass than uninoculated control and improved growth in height (8.8 m), stem girth (9.6 cm) and tissue nitrogen content (3.3 mg/g) than uninoculated controls in field condition [112]. Frankia inoculated Casuarina seedlings planted in farm forestry improve the tree growth and biomass in the field condition [2, 112] and improve the nutrient cycling of actinorrhizal plants through high amount of litter production and decomposition [113]. Combined inoculation of Azospirillum, Phosphobacteria, AM fungi and *Frankia* produced excellent growth and biomass of *C. equisetifolia* seedlings due to co-inoculation with *Frankia* through improved nitrogen fixation [22, 114] (**Table 1**).

### **10. Methods of inoculation**

#### **10.1 Inoculation methods of** *Azospirillum, Rhizobium* **and phosphobacteria**

Seed or nursery stage is best for application of bio-fertilizers. Suitable methods for forestry species is seed coating and inoculation in polythene bag. Two grams of carrier culture (10<sup>−</sup><sup>8</sup> cfu/g) can be applied in rhizosphere of seedlings in the polythene bags in the nursery.

#### **10.2 Inoculation with seeds**

Inoculation requirement varies from the size of the seeds. Normally 200 g of lignite/peat soil based culture (108 cfu/g) is need for every 8–10 kg of seeds of the tree species. A slurry is formed by mixing the inoculant with cooled rice gruel (250 ml). The required quantity of seeds is added in the slurry and mixed thoroughly so that each seed is coated with the black colored inoculant. The treated seeds are then shade dried for 30 min and sown.

#### **10.3 Inoculation in the nursery mother bed**

Two hundred grams of lignite based carrier culture of *Rhizobium* or *Azospirillum* (108 cfu/g) is required for 4 m × 1 m mother bed. It has to be spread uniformly and mixed thoroughly before sowing of seeds.
