Trees are increasingly grown on-farm to supply wood and biomass needs within developing countries. Over the last several decades, within the irrigated rice-wheat growing lands of northern India, fast-growing poplar trees have been planted on tens of thousands of small farms. Recent debate regarding afforestation has raised the issue that water use is often increased when trees are planted. This ongoing debate focuses primarily on afforestation or reforestation of upland and rain-fed agricultural areas, and off-site impacts such as reduced streamflow. Adoption of poplar agroforestry in northern India, in contrast, is occurring in areas where land and water are already intensively used and managed for agricultural production. This study based on farmer survey data, used remote sensing and spatial hydrological modeling to investigate the importance and role of the poplar trees within the agricultural landscape, and to estimate their water use. Overall, results illustrate a potential for addressing the increasing global demand for wood products with trees grown on-farm within irrigated agroforestry systems.

Trees and water: smallholder agroforestry on irrigated lands in Northern India

Energy balance and economic benefits of two agroforestry systems in northern and southern China.

Poplar (Populus deltoides Bartr.) based agroforestry systems are economically viable and more sustainable than many other crop rotations prevalent in northern India. Growth {girth at breast height (GBH) and height} and productivity (volume) of clone G-48 of poplar spaced at 5 x 4 m, soil organic carbon (OC), and concentration of available macronutrients (N, P and K) and micronutrients (Zn, Fe, Mn and Cu) in surface soil (0-15 cm depth) were determined at an interval of six months starting from April 2002 till October 2003 in one and four year old (in January 2002) 16 poplar plantations on farmers' fields in Ludhiana, Punjab. The observations were taken from plantations having fodder {sorghum (Sorghum bicolor)/pearlmillet (Pennisetum americanum) in summer}-wheat (Triticum aestivum) (in winter) rotation throughout the poplar age and those having sugarcane (Sachharum officinarum) initially during two years and fodder-wheat rotation thereafter. The GBH, height and volume of younger plantations intercropped with fodder-wheat rotation were 15.6, 17.2 and 46.7%, respectively higher than that of plantations intercropped with sugarcane. Growth increment of poplar was markedly higher during April to October than October to April. Soil OC was significantly greater in older (6.83 g kg-1) than the younger (5.35 g kg-1) plantations. Available macronutrients in soil increased at successive sampling times. The average Zn concentration at final sampling was 17% lower compared to initial sampling, whereas the other micronutrients tended to increase during April 2002 to October 2003 and the increase was higher in four year old plantations than one year due to higher inputs of organic matter.

Tree growth and nutrient status of soil in a poplar ( Populus deltoides Bartr.)-based agroforestry system in Punjab, India

Factors influencing the sustained participation of farmers in participatory forestry: a case study in central Sal forests in Bangladesh

Effects of tree shading on crop within agroforestry system in the oasis regions or under irrigation agriculture are poorly understood. Objective was to determine maize yield variation and its reasons when tall Poplar trees (Populus gansuensis) were grown in western and eastern margins of the crop field in Hexi Corridor desert oasis in northwestern China. Maize growing among the 50 m alley space were divided into five regions, including shading region in western side (W-S), non-shading region in western side (W-NS), middle region (M), shading region in eastern side (E-S) and non-shading region in eastern side (E-NS), for all measurements. Measurements of leaf area expansion were carried from seeding to flowering stage, photosynthetic physiological parameters and microclimate characteristics were measured at booting stage, grain yield and other harvest parameters were obtained at harvest time. We found that tree shading reduced the crop yield by 27 and 22% in western and eastern regions, respectively, and also, mean crop yield for western side was 23% lower than eastern side. The direct reason of yield variation was transpiration rate (E) variation at booting stage, that is, maize which had higher daily mean E would obtained higher yield. Moreover, changes of incident photosynthetically active radiation (PARi), air temperature (T
 a) and CO2 concentration (C
 a) were the basic reasons of yield variation among different regions. Because higher PARi, higher T
 a and lower C
 a, which caused by the tree shading, would all led to higher E and finally higher crop yield.

Effects of tree shading on maize crop within a Poplar-maize compound system in Hexi Corridor oasis, northwestern China

To meet raw material requirements, Wimco, the biggest manufacturer of matches in India, has been promoting poplar-based agroforestry through an agroforestry project since 1984 approved by the National Bank for Agricultural and Rural Development (NABARD) in the northern region of India. This study aims at evaluating the performance of poplar-based agroforestry in terms of income, employment and environmental impact from the farmers' perspective. Poplar-based agroforestry is economically viable and more profitable than many of the crop rotations followed in the study area. This land-use system is also capable of providing employment opportunities on farms. Sensitivity analyses indicate that this system is not highly risky. However, costs charged by Wimco for technical advice substantially reduce the income from poplar plantation. With agroforestry experience, farmers can expect high dividends in subsequent rotations. Life-time matrices developed through group interviews are useful for thorough economic analyses of agroforestry projects, particularly in cases where data over a period of time are not available.

P. Singh

Papers

Economic analysis of industrial agroforestry: poplar (Populus deltoides) in Uttar Pradesh (India)