S. Puri

Agroforestry research for development in India: 25 years of experiences of a national program

India has been in the forefront of agroforestry research ever since organized research in agroforestry started world-wide about 25 years ago. Considering the country’s unique land-use, demographic, political, and sociocultural characteristics as well as its strong record in agricultural and forestry research, India’s experience in agroforestry research is important to agroforestry development, especially in developing nations. Agroforestry has received much attention in India from researchers, policymakers and others for its perceived ability to contribute significantly to economic growth, poverty alleviation and environmental quality, so that today agroforestry is an important part of the ‘evergreen revolution’ movement in the country. Twenty-five years of investments in research have clearly demonstrated the potential of agroforestry in many parts of the country, and some practices have been widely adopted. But the vast potential remains largely underexploited, and many technologies have not been widely adopted. This situation is a result of the interplay of several complex factors. The understanding of the biophysical issues related to productivity, water-resource sharing, soil fertility, and plant interactions in mixed communities is incomplete and insufficient, mainly because research has mostly been observational in nature rather than process oriented. Methods to value and assess the social, cultural and economic benefits of various tangible and nontangible benefits of agroforestry are not available, and the socioeconomic processes involved in the success and failure of agroforestry have not been investigated. On the other hand, the success stories of wasteland reclamation, and poplar-based agroforestry show that the technologies are widely adopted when their scientific principles are understood and socioeconomic benefits are convincing. An examination of the impact of agroforestry technology generation and adoption in different parts of the country highlights the major role of smallholders as agroforestry producers of the future. It is crucial that progressive legal and institutional policies are created to eschew the historical dichotomy between agriculture and forestry and encourage integrated land-use systems. Government policies hold the key to agroforestry adoption.

Effect of auxins (IBA and NAA) and season on rooting of juvenile and mature hardwood cuttings of Robinia pseudoacacia and Grewia optiva

Juvenile (2 year old trees) and mature hardwood (15 year old trees) cuttings of Robinia pseudoacacia and Grewia optiva were tested for their capacity to form roots. Cuttings were prepared in spring, monsoon and winter seasons and treated with different concentrations (250, 500 and 750 mg/l) of IBA and NAA. These were planted in a mist chamber maintained at 25 ± 1 °C with relative humidity > 70%. Juvenile cuttings of both species rooted significantly better than mature hardwood cuttings in all three seasons, and the age effect was more pronounced in auxin treated cuttings. The highest rooting in juvenile (83.3%) and mature (66.6%) cuttings was observed with the NAA (500 mg/l) treatment in R. pseudoacacia during the spring season. In G. optiva, IBA (250 mg/l) in the monsoon season was most effective and yielding a maximum of 80% and 70% rooting in juvenile and mature cuttings, respectively. Auxin treatments also significantly enhanced the number of roots, root length, leaf number and leaf area. Statistical analysis of data revealed that interactions between age, season and treatments were significant at P < 0.05 level for R. pseudoacacia and non-significant for G. optiva.

Growth, biomass, carbon storage and nutrient distribution in Gmelina arborea Roxb. stands on red lateritic soils in central India

Growth, biomass, carbon storage and nutrient (N, P and K) variations in 1 to 6-year-old chronosequence plantations of Gmelina arborea were studied in three degraded red lateritic sites in central India. Growth parameters (dbh, total height and number of branches) varied significantly due to difference in age and site quality, but tree density showed non-significant variation. Stand biomass ranged from 3.94 (1-year-old) to 53.67 Mgha(-1) (6-year-old) and stand carbon in 6-year-old plantations ranged from 24.12 to 31.12 Mgha(-1) at different sites. Among the tree components, the stem wood accounted for maximum C (56.25% at site 1) followed by branches (19.8% at site 3), roots (18.51% at site 2) and foliage (7.01% at site 3). Mean annual C accretion at 6 years age of plantation was highest in site 3 and it was 0.35, 2.66, 0.965 and 0.87 Mgha(-1) for leaf, stem, branches and roots, respectively. Quantity of nutrients increased with age. Total nitrogen accumulation in 6-year-old stands at the three sites ranged from 212.9 to 279.5 kgha(-1) with a mean annual storage of 238.43 kgha(-1) and total K ranged from 170.8 to 220.5 kgha(-1) with a mean annual storage of 189.93 kgha(-1). Phosphorous accumulation was lowest with a mean storage of 16.75 kgha(-1). The organic carbon and nutrients in the soils improved significantly after 6 years of G. arborea planting. Soil organic carbon increased from 8.46 to 14.02 Mgha(-1) within 6 years. At soil depths 0-20 cm, 21-40 cm and 41-60 cm, available N enhanced by 14.85%, 11.98% and 11.25%, K by 10%, 9.13% and 10.63%, whereas phosphorous declined by 26%, 23% and 20%, respectively. At 6 years, G. arborea stands sequestered 31.37 Mgha(-1) carbon. The nutrient management strategies in relation to carbon accretion in G. arborea stands on degraded lateritic sites are discussed.

Propagation ofRobinia pseudoacacia Linn. and Grewiaoptiva Drummond from rooted stem cuttings

Rapid vegetative propagation of promising multipurpose trees is an important need in agroforestry development. Grewia optiva andRobinia pseudoacacia are two such species, about the propagation of which very little is known. The rooting ability of stem cuttings harvested from juvenile (2 year-old) and mature hardwood(15 year-old) trees of Robinia pseudoacacia andGrewia optiva was significantly influenced by the period or season of harvesting cutting. Juvenile cuttings of both species rooted significantly better (42.9% in R. pseudoacacia and 46.6% in G. optiva) than mature hardwood cuttings (34.7% in R.pseudoacacia and 41.4% in G. optiva). The effect was more pronounced in auxin treated cuttings. InR. pseudoacacia, the highest rooting in juvenile(83.3%) and mature (66.6%) cuttings prepared in spring season was observed with the NAA (500 mg/l) treatment. InG. optiva, IBA (250 mg/l) in the monsoon season was most effective and recorded a maximum of 80% and 70%rooting in juvenile and mature cuttings, respectively. The auxin treatments also significantly enhanced the number of roots (23.8 inR. pseudoacacia and 17.6 in G.optiva) and their mean length (14.3 cm inR. pseudoacacia and 16.1 cm inG. optiva). Interactions between age, season and treatments were significant at P < 0.05 level for rooting percent in R. pseudoacacia and non-significant for G. optiva. The results of this study suggest that it is possible to develop clones of genetically superior trees of R. pseudoacacia and G.optiva for use in agroforestry or afforestation programmes.

Geographical variation in rooting ability of stem cuttings of Azadirachta indica and Dalbergia sissoo

Geographical variations are among the least studied factors that control or modify rooting by cuttings. In the present study 1 year old branch cuttings of 12 provenances from Central India of Azadirachta indica and Dalbergia sissoo were examined for variation in rooting ability. Application of 500 mg/l-1 indole butyric acid (IBA) significantly increased (P < 0.05) root numbers, root length, root dry weight, rooting percentage, shoot number and shoot height. The auxin treatment amplified the provenance differences in rooting ability of cuttings. No significant variation in survival was evident with respect to provenance or auxin treatment. Correlation coefficients for root parameters were positive and significant (P < 0.01) and results of principal component analysis identified rooting factor having 52.3 and 46.7% of the total sub-plot mean variance among auxin treated cuttings for A. indica and D. sissoo, respectively. On the basis of overall performance of rooting in cuttings among provenances, the Raipur provenance was adjudged the best. Opportunities to develop genetically diverse clonal production stands are discussed.

Growth and biomass production in Azadirachta indica seedlings in response to nutrients (N and P) and moisture stress

Production of quality seedlings is an important aspect of successful tree planting. No information is available on the effect of nutrients and water on the growth and development of the seedlings of neem (Azadirachta indica A. Juss), an important component of many tropical agroforestry systems. In an experiment in central India, the growth and nutrient-use efficiency of neem seedlings grown at various levels of light, nutrients (N and P), and water stress were determined. Seedlings were given light (diffused and complete) and nutrient (N and P) treatments comprising either high N-high P, high N-low P, low N-high P, or low N-low P. Seedlings grown in complete light (800 μ mol/m2/s) had four times more biomass than those grown in diffused light (200 μ mol/m2/s). Significant increase in seedling biomass was observed with nitrogen application, while phosphorus had no effect on biomass. Leaves contributed maximum biomass, followed by roots and stem. Nutrient use efficiency decreased with an increase in the supply of nutrients. In another experiment, containerized and bare-root seedlings were subjected to five watering treatments, viz., watering twice a week, watering weekly, watering every alternate week, watering every third week, and natural precipitation. Plant moisture stress affected both growth and survival of neem seedlings. Only 50 per cent of seedlings survived in severe drought treatment (no. 4) whereas 90 to 95 per cent seedlings showed growth in all other treatments. Plant moisture stress in severe drought treatment averaged −21 bar while in other treatments it ranged from −9 to −12 bar. Shoot-root ratio was high in bare-root seedlings as compared to containerized seedlings. Containerized seedlings had shown better endurance against drought than the bare-root seedlings. The results suggest that neem seedlings adjust their nutrient use efficiency and can be grown even under limited available resources. It is also inferred that the species can tolerate soil resource depletion caused by competitor species.

Relationship of water to adventitious rooting in stem cuttings of Populus species

Populus species, characterized by fast growth and easy vegetative propagation, are widely used in agroforestry practices. The substantial water requirement of poplars make them interesting subjects for water balance studies. No information exists on soil moisture requirements for initial root and shoot growth of Populus cuttings. This study on leafless hardwood cuttings of Populus x euramericana (Dode) Guinier cv. ‘Robusta’ examined the dynamics of water use during propagation, as influenced by two initial soil water potentials (−0.006 and −0.06 MPa). Differences in the initial water potential of the cuttings was achieved by three pretreatments i.e., fresh, soaked and dried. Initial Ψshoot was −1.45, −0.10 and −2.10 MPa in fresh, soaked and dried cuttings, respectively. Soil moisture had a major effect on rooting. Water-stressed cuttings took a longer time to root and had fewer roots. Pre-soaking of cuttings stimulated rooting, particularly under the drier soil moisture conditions. Initially the water potential of cuttings decreased with time and with the formation of roots it stabilized in all the pretreatments. The reduction in water potential of cuttings after planting was related to an increase in resistance to water flow in the xylem.

Evaluation of Populus deltoides clones under nursery, field and agrisilviculture system in subhumid tropics of Central India

Populus deltoides Bartr., a native of North America, is generally grown in India above latitude 28 °N. One hundred and six clones were evaluated for four years at Raipur situated at 21°12′N latitude and 81°36′E longitude. These were grown on vertisol soil. Based on growth and survival performance in the nursery for two successive years, nineteen clones were selected for field evaluation. The best five clones (G3, G48, 65/27, D121 and S7C1) were planted in an agrisilviculture system at a spacing of 4 × 4 m with soybean grown as an intercrop. After 4 years these clones had an increment of DBH by 66.5 to 77.5% and of height by 42.2 to 78.6% within one year when compared to that observed at 3 years of age. In rank order of growth the best five clones were 65/27 > G3 > D121 > G48 > S7C1. Total biomass varied between 20.9 to 35.8 Mg ha−1 in different clones. Among the tree components, stemwood accounted for 52–61% of the total biomass, followed by branches (20–25%), bark (9–13%) and leaves (7–10%). No significant variation between net primary productivity and photosynthetic efficiency was found in different clones. Soybean productivity decreased as the trees aged, reaching 40.5 to 58.1% in 4-year-old trees.

Establishment of Prosopis cineraria (L.) druce in the hot deserts of India

Prosopis cineraria (L.) Druce, commonly known as Jandi, is a deep rooted, nitrogen fixing, multipurpose tree endemic to the hot deserts of India. These trees are the essential component of the agroforestry land use system in these parts of India. The shade-intolerant tree reproduces poorly in nature and is difficult to propagate vegetatively. Germination up to 86.6% was observed after 15 days in seeds soaked in water at room temperature for 72 h. In another treatment, pouring of boiling water twice (at 0 and 6 h) over seeds and germinating after 12 h produced germination rates of 92.6%. Field establishment of containerized transplants in polythene bags (22×10 cm; 150 gauge) gave 90.3% survival after 6 months and 75.4% survival after 24 months. Seedlings were irrigated once during transplanting with 15 1 water. Bare root transplants and manual direct seeding after 6 months had a survival of 30.8 and 45.0%, respectively. Increased levels of nutrients (N, P and K), moisture content and organic carbon were observed under plantations as compared to open areas.

Effect of soil and plant water relations on rooting of Populus × euramericana stem cuttings

Studies on Populus ×euramericana (Dode) Guinier cv. ‘Robusta’ wereconducted to examine the rooting behaviour and changes in water potentialduringrooting, as influenced by the initial water potential of the cutting at twosoilwater potentials (−0.006 and −0.06 MPa). Differencesinthe initial water potential of the cuttings was achieved by three pretreatmentsi.e., fresh, soaked and dried. Initial Ψshoot was −1.45,−0.10 and −2.10 MPa in fresh, soaked and driedcuttings, respectively. Soil moisture had a major effect on rooting. Waterstressed cuttings took a longer time to root and had fewer roots. Pre-soakingofcuttings stimulated rooting particularly under the drier soil moistureconditions. Initially the water potential of cuttings decreased with time andwith the formation of roots it stabilized in all the pretreatments.Resistance-to-flow measurements suggested the development of tyloses and theestablishment of new xylem. No relationship was evident between stomatalresistance of leaves and water potential of cuttings. The starch content of thestem cuttings decreased significantly with time irrespective of treatment.