Extension and motivational efforts

A strong extension network involving local influential persons plus non-government (NGO) and Government agencies was established. Farmer meetings were organized to develop awareness among the farmers regarding the economic benefits available from pulpwood plantations. To instill confidence in this system we organized exposure visits to successful plantations in Andhra Pradesh, where an extensive area was covered with leucaena plantations, and to our mill and R&D Centre. Promotional stalls were established at different agricultural exhibitions in Gujarat and Maharashtra giving demonstrations regarding the economic and environmental benefits of plantations (Table 1).

Table 1 Numbers of farmer meetings, farmer tours and visits to agricultural exhibitions. 

Site preparation

Leucaena plantations were established within a 0‒350 km radius of the mills in Gujarat and Maharashtra States. The majority of soils are black alkaline soils formed from basalt rock and the major agricultural crops are cotton, sugarcane, banana, papaya, black gram, green gram and Cajanus cajan. Deep ploughing with a mould-board plough followed by harrowing was recommended and organic manures such as cow dung were added prior to sowing. Most plantations are under a drip irrigation system.

Establishment procedures

Most farmers adopted tree spacings from the following range: 1.2 × 1.2 m, 1.5 × 1.0 m, 1.5 × 1.2 m and 1.0 × 3.0 m, which allowed intercropping in the first year. Seed was treated to ensure uniform and fast germination (70‒80%), a critical factor in establishment of leucaena plantations. Methods for breaking leucaena seed dormancy included chemical treatment (99% H₂SO₄) and mechanical scarification with a Kimseed seed scarifier imported from Australia.

Seed is sown at the onset of the monsoon, i.e. in June-July, with 2 or 3 seeds per hole and irrigation is available at the time of sowing. Following germination, weeding is performed and leucaena plants thinned to 1 healthy seedling per location when they reach a height of 15-20 cm.

The establishment cost of leucaena plantations is US$ 688/ha.

Rhizobia inoculation

Establishment of the rhizobium association proved to be sporadic. In order to enable faster growth, rhizobium cultures/colonies from different areas were tested with the help of M/s PAC Bio Fungbact Pvt Ltd, Madhi, Gujarat. It was found that a mixture of all rhizobia was best for helping development of profuse nodulation in seedlings (Figure 3). With the help of M/s PAC Fungbact Pvt Ltd, a rhizobium culture was developed in powder form and is being supplied to farmers along with seeds, where it is coated on seeds prior to sowing.

Figure 3 Rhizobial nodulation in leucaena. 

Protection and maintenance of plantations

Where irrigation is available, it is applied every 15‒30 days depending on soil moisture conditions. Fertilizer applications are based on soil testing and comprise 50 g NPK (12:32:16)/plant on 2 or 3 occasions for the first 2 years. In potash-deficient soils, an additional 50 g potash/plant is applied. Application of good quality organic manure is recommended, but no grazing, browsing or trampling is allowed. Termite damage is controlled by applications of 0.05‒0.10% chlorpyriphos (5‒10 mL/L of water) to soil around the base of the plant.

Agroforestry intercropping with leucaena

Intercropping of leucaena plantations in the first year is often practiced with cotton, ground nut, pigeon pea, green gram, bananas, onions, pigeon pea, chilli, castor oil, sugarcane or ginger. Farmers find that leucaena has no adverse effects on crop production in the first year. They report a range of benefits of intercropping, including:

Productivity improvement through Candidate Plus Trees [CPTs]

In order to have a broader genetic base and to improve yield per unit area, a systemic genetic approach in research and development of leucaena is being undertaken. Selection of CPTs in Gujarat and Maharashtra States at different sites is in progress. To date, about 1,300 CPTs have been selected. A further short list of the top 10 CPTs was selected for testing of pulping properties at our R&D laboratory. Screened pulp yields (pulp/fiber % of wood) varied from 47.2 to 51.4% (Table 2), slightly higher than the present average screened pulp yield of commercialized leucaena clones (about 47%). We have also collected coppice cuttings from these CPTs and have developed rooting methodologies in misting chambers.

Table 2 Pulp quality, chemical consumption, pulp viscosity, pulp brightness, cooking condition for pulp yield for leucaena wood samples collected from 6 Candidate Plus Trees (CPTs). 

¹Cooking chemical for pulping (AA) as Na₂O (%) refers to % of white liquor required for cooking/pulping of wood chips in digester.

²Kappa number: an indication of the residual lignin content or bleachability of wood pulp by a standardized analysis method.

³BDMT = Bone dry metric tonne (= at 0% moisture).

Progeny testing for these CPTs is on-going. Initial results show that CPM 3, CPM 29 and CPM 32 have 125% growth compared with the control of existing leucaena field clonal plantations. Vegetative multiplication is on-going for further multi-location trials. Presently we are producing 6 leucaena clones and many more are in the pipeline to be released shortly.

Hybridization program in leucaena

In the first phase of this program, potential species used for crossing to produce hybrid vigor and higher pulp yield and wood production were Leucaena collinsii and L. leucocephala (CPM 11 and CPM 16 clones).

Leucaena collinsii, which is diploid (2n) with 52 chromosomes, was fast-growing and resistant to psyllids (Heteropsylla cubana) and grew up to 8‒10 m in height in 2.5‒3 years. It also produced less seed, resulting in faster vegetative growth.

The clones of L. leucocephala, which is a tetraploid (4n) with 104 chromosomes (^{Brewbaker 1988}), were also fast-growing and grew up to 10‒12 m in height in 2.5‒3 years but were susceptible to the psyllid insect, resulting in loss of growth for 8‒9 months in a 3-year rotation cycle. This species produced abundant seeds, resulting in less vegetative growth during seeding. L. leucocephala (CPM 16) was used as a male parent and L. collinsii as the female parent. About 100 flowers were emasculated for crossing and observed for maturity of their stigmas. The calyx was sprayed with IAA to avoid abscission of flowers during hybridization (^{Sorensson 1988}), and all remaining flowers were removed. We produced 15 pods through this hybridization and subsequently grew seedlings in plastic containers from the seeds (Figure 4). A hybridization test carried out at JK Agrigenetics Ltd, Hyderabad confirmed that they were true hybrids (Figure 5). We planted progeny trials to study growth of the hybrids in the field. As L. leucocephala is tetraploid and L. collinsii is diploid, the hybrid is triploid and fully-sterile and hence must be multiplied from rooted cuttings. This work is on-going.

Figure 4 Breeding of L. leucocephala and L. collinsii. 

Figure 5 Leucaena samples- 1: K636 (mutated); 2: K636; 3: CPM 11 (mutated); 4: CPM 11; 5: CPM 16 (mutated); 6: L. collinsii; 7: CPM 16; 8: L. collinsii (mutated); 9: KX2; 10: CPT 32; 11: CPT 3; 12: CPT 29; 13: Hy 1; 14: Hy 2; 15: Hy 3; 16: Hy 4. Status of sample 6 (L. collinsii) - diploid; sample 7 (CPM 16) - tetraploid; samples 14, 15 and 16 - triploid ‒ was confirmed as true hybrids by JK Agrigenetics. 

Mutation techniques in leucaena

We used gamma ray mutation techniques for alteration of gene structure, which may transmit to coming generations. We irradiated leucaena seedlings of K636 (known as cv. Tarramba in Australia), L. collinsii, L. leucocephala clone CPM 11 and L. leucocephala clone CPM 16 with different frequencies of gamma rays at the nuclear research station, Indian Agriculture Research Institute, New Delhi and laid out progeny trials in August 2016 for studying the effects of mutations.

Based on the superior induced growth in some mutants, DNA fingerprinting analysis was carried out, which confirmed that mutations altered the gene structure and growth has been accelerated. Vegetative multiplication of positive mutants is on-going for further trials.

Clonal hedge garden techniques

A naturally ventilated polyhouse covered with 200 micron polythene stabilized against UV rays and provided with a fertigation system, plus temperature and humidity controllers, was constructed. Superior mother plants were planted in raised beds filled with pure sterilized sand at 10 × 10 cm spacing. Required fertilizer dosages were pro- vided to the plants through the fertigation system and constant humidity and temperature were maintained. Every month about 3 or 4 juvenile coppice cuttings were obtained from each mother plant. The adequate nutritional status of the mother plants was important in increasing the rooting percentage of cuttings in the misting chamber.

Propagation techniques

Cocopeat was used for clonal propagation as it has low salinity as measured by electrical conductivity (EC). It also has excellent water holding capacity and cation exchange capacity. Fifty mL, 60 cell plastic root trainer blocks were used for production of clones (^{Lal 2001}). Misting chambers with appropriate temperature and humidity control systems were installed over a 3,200 m² area at the clonal propagation centre in Songadh. Every month about 150,000 juvenile apical cuttings are established producing 1 million leucaena clones per annum. Water quality is critical for a successful misting chamber operation. Water used has a pH of 6.5‒7.5, very low EC and sodium absorption ratio below 3. Reverse osmosis water rather than canal or river water is preferable for misting chamber operation (^{Brewbaker 1988}).

Increased plantings

To date the CPM Unit has promoted the establishment of approximately 50,000 ha of social and farm forestry plantations in Gujarat and Maharashtra States (Figure 6) involving about 66,000 farmers. Similarly, 18,400 ha of leucaena plantations have been established by approximately 7,800 farmers (Figure 7).

Figure 6 Annual increases in area under seedling and clonal plantations (ha). Note: The area planted in the year 2016/17 was low due to higher wood availability and lower wood requirement. 

Figure 7 Annual increases in area under leucaena plantations (ha). 

Wood generated from plantations promoted by JK Paper Ltd is being used for making paper, plywood, poles and furniture. The expected annual increase in value of wood is given in Figure 8. JK Paper Ltd, CPM unit plantation initiatives are creating sustainable livelihoods among nearby farmers by creating economical wood assets on their farm lands.

Figure 8 Estimated and projected wood asset value of plantations in millions of USD. 

Survival, productivity and environment

Hi-tech clonal plantations in areas surrounding the mill have >90% survival. With continuous research and development efforts, site-specific, disease-resistant, fast-growing and high-yielding clones achieved a productivity of 30‒50 t/ha/yr.

The value of JK Paper Ltd farm forestry program is immense in mitigating environmental degradation. Apart from increasing greenery and tree cover, farm forestry has significant potential for carbon storage. Estimated quantities of CO₂ extracted from the air and C stored by farm forestry during the period 2012/13 to 2016/17 are shown in Table 3.

Table 3 Estimated annual carbon storage and CO₂ absorption by standing plantations.