Introductory Agroforestry (1+1)

INTRODUCTION

Botanical Name : Populus deltoides Bartr.
Family : Salicaceae
Local Name : Poplar, Paharipipal

Plate 13.1 Poplar tree

Introduction

• Poplars are amongst the fastest growing tree species under appropriate agro climatic conditions.
• Poplars can be harvested at short rotations of 8 to 10 years, even earlier in good sites.
• Wood obtained from poplars is eminently suitable for manufacture of match splints, veneering products, artificial limbs, interior paneling, cheap furniture and packing cases etc.
• Poplars show straight and cylindrical bole, moderate conical crowns mostly deciduous during winter months,
• Combine well with inter-cultivation of agriculture crops.
• These features combined with good economic returns and availability of long-term bank loans have made versatile poplars the most popular tree species for planting under agro forestry system in the irrigated tracts of north-western plains of India
• Five indigeneous species viz Populus ciliata, P. laurifolia, P. gamblei, P. alba, P. glauca, are found along water courses in Himalayan region.
• However, success story of poplar plantations in the north-western plains of Uttar-Pradesh, Haryana, and Punjab is based on exotic P. deltoides indigenous to United States of America.
• Certain clones of P. deltoides have been found to be eminently suitable for a afforestation as well as agroforestry plantation. P deltoides clones G-3, G-48 (Australian selections) and D-121 (American selections) constitute bulk of these plantations.
• Additional clones like D-61, D-67, S-7C-8 and S-7C-15 have also been included in the plantation programme. Poplars can attain 90 cms girth at breast height and mean annual increment of 20m³/ ha at 8 years rotation under good care.

Description

• Populus deltoides is a fast growing tall tree with a fairly straight and slim trunk, rather open crown composed of a few large branches and attaining a height of 30 m and girth of 2 m.
• The branches are more or less angled or almost winged, the side branches borne on large branches are shed early.
• Outer bark forms early, furrowed by cork-like ridges and deep fissures.
• The leaves are fairly large, deltoid on short shoots and very large and cordate on long shoots, light green in colour.
• They are 10-18 cm long, acuminate, crenate-dentate with long petiole.
• The male catkins 7-12 cm long, 40-60 stamens per flower and produce wind-borne pollen. The female catkins are 15-25 cm long.
• The female flowers have single-celled ovary with numerous ovules and at anthesis have 2-4 prominent stigmas.
• Fruit ovoid capsules, hanging in loose clusters, opening by 3-4 valves and seed is small and hairy.

Distribution

• P. deltoides clones have been cultivated in a number of countries.
• In fact, P. deltoides and their hybrids together make about 90 percent of the total cultivated poplars of the world (FAO, 1979).
• Among the countries in which they have been cultivated are West Punjab in Pakistan, Middle East, New South Wales in South Australia, Parana Delta and north eastern continent part of the province of Buenos Aires, Argentina (Singh, 1982).
• In India, it has been successfully cultivated as a forest crop or agroforestry crop in the Indo-Gangetic plains and in the Terai region of Uttar Pradesh.
• Poplars have been raised at slightly lower latitudes also, but it is only above 28° N, that they had fair success in experimental plantations and on farms.
• On experimental scale, Populus deltoides has been successfully cultivated at Jorhat (Assam) at an altitude of 96.5 m.
• In its natural range in the southern part of USA, P. deltoides occurs primarily on bottom lands along rivers and other water ways.
• In West Punjab (Pakistan) and Middle East, it is cultivated only where irrigation is available.
• In areas where its cultivation has been tried without irrigation, the growth has been very poor.
• In not adequately irrigated plantations in the Middle East, P. deltoides is reported to become susceptible to the major wood borer Melanophila picta.

SITE FACTOR
SOIL

• Populus deltoides can survive on soils varying from sandy loam to fairly stiff clay, but it makes its best growth on moist, well-drained, deep, medium-textured, alluvial soils that are fertile and well-aerated.
• The nursery plants perform better on clayey soil than on sandy soil. Coarse sands and heavy clayey soils deficient in organic matter are unsuitable.