FOREWORD

This report offers a critical review of background material available on the species known as tamarugo, Prosopis tamarugo Phil., (Mimosaceae), native of northern Chile.

The main purpose of the analysis is to contribute further, although by no means exhaustively, to what is already known about this interesting desert fodder tree, in the hope of stimulating more research along these lines in Chile, and encouraging experimentation in desert areas elsewhere in the world.

The desert ecosystem of the Tamarugal Pampa is highly specific. The climate is the normal desert climate; the most biologically significant connotations are: high day-time temperatures, great day-to-night temperature range, almost total lack of rainfall, occasional mist, relatively low humidity and intense sunlight. The soils are composed of deposits of fluvial origin from the cordillera of the Andes, and have a surface salt crust ranging in thickness from 0.10 m to 0.60 m, or more.

Man-made tamarugo plantations are being introduced in the Tamarugal Pampa which are transforming the absolute desert ecosystem into an agro-ecosystem. The result, so far, has been a noteworthy increase in overall productivity in one of the most inhospitable regions of the world. The major objective of this programme, begun in 1963, is to utilize tamarugo as a means of gaining income.

Studies on animal production and behaviour were accompanied by studies on afforestation, the physiology of this tree, and research on the desert's most valuable and scarcest resource -- water.

These initial studies defined the adaptation capacities of certain animal breeds, the resistance of tamarugo to salinity and how its tap roots use groundwater. The studies revealed a highly significant fact: under certain conditions of atmospheric humidity, tamarugo absorbs water through its leaves, transporting it to the root system and depositing it in the micro-rhizosphere, whence it is reabsorbed along with the soil nutrients.

This latter feature explains why measurements of mean annual evaporation show much higher rates outside than inside the forest area, where a mere fraction of the water is lost in evaporation. This is also why tamarugo trees are found in areas where the groundwater table lies 40 or more metres deep and has no contact with the roots of trees.

With the above brief preamble, we offer this work. It is intended as a step forward towards more knowledge about this singular desert fodder tree, in the hope of benefiting people living in the vast arid zones of our planet.

Fernando Riveros
Officer-in-Charge
Grassland and Pasture Crops Group
Plant Production and Protection Division
Food and Agriculture Organization of the United Nations
Rome, Italy

INTRODUCTION

This report has been divided into four parts in order to develop the subject more fully and make it easily comprehensible.

Part One gives general data on the genus Prosopis, the habitat where P. Tamarugo is found, and the launching of a combined grazing and forestry programme. Prosopis is distinguished, especially in the Western Hemisphere, for its direct link with the activities of primitive man and its subsequent usefulness as a component of development in arid zones. The tamarugo has been used exhaustively for firewood in mining operations in the Tamarugal Pampa in northern Chile. Here, in recent years, man-made plantations have opened up new horizons for stock-raising and for the social and economic development of the region.

Part Two deals exclusively with the basic subject matter of this report: P. tamarugo, a native of the Tamarugal Pampa. The tree produces abundant fodder, palatable to sheep, cattle and goats, and contains 12% crude protein, 30% fibre and 1.9% ether extract. The digestibility of the fruit breaks down into 13.89% protein; 1.16% ether extract, 28% free nitrogen extract, and total digestible nutrients, 50.58%. The average yield of fruit per tree is 2.10 kg/m² of crown projection. This figure is even higher for adult trees. The distribution, biology and behaviour of the twelve most relevant tamarugo insect pests, some endemic to the area, are described.

Part Three covers the multiple and complex facets of animal production. The species and breeds which have proved most suitable to this ecosystem are Angora goats, Karakul and Suffolk Down sheep, Hereford beef cattle and breeds crossed with Hereford. Daily fodder consumption, including fruit, has been studied from the standpoint of nitrogen balance and has shown that animals maintained a positive balance, the total digestible nutrients being considered comparable to those of a good quality fodder, such as alfalfa.

Part Four looks at the geographic features of the Tamarugal Pampa, analyzing such abiotic factors as climate, geomorphology, hydrology and soils.