Showing papers on "Marginal land published in 1992"

Farming System Research and the quest for a sustainable agriculture.

Abstract: This paper brings together information from four sites in sub-Saharan Africa where FSR&D projects are located (Mali, Benin, Zambia and Tanzania), supported by the Royal Tropical Institute of The Netherlands. Common environmental constraints to agricultural productivity are analyzed, with an emphasis on aspects of soil fertility maintenance. It is shown that when plant nutrients are valued against market prices, annual crop production systems are inefficient due to considerable losses of nutrient resources (e.g., soil erosion) and economically unviable because of unfavourable input and producer price ratios. Technically solutions are available that make agriculture sustainable, but its output is likely to be reduced when accepting the need for environmental protection at various levels of integration (cropping system, field/farm, village territory, etc), since marginal land must be left under natural vegetation, and various forms of buffering elements must be installed on farms. The costs of protective measures (space, labour, energy in community organization) cannot be raised based upon local resources currently available. Making small farmer agriculture in the tropics sustainable and environmentally sound begins by improving economic conditions for farmers, raising producer income and lowering prices for inputs.

Contour hedgerows and other soil conservation interventions for hilly terrain

Abstract: Management of hillside cropland is a critical issue in the tropical world because of the extreme pressure on the land itself that results from the decision to farm what would be considered in many countries as marginal land. Practices such as contour hedgerows and other soil conservation techniques could be more effective if they are installed or aligned in such a way that they maximize the land capability potential in various sectors of typical soil catenas; and if biological control crops including trees, grasses and shrubs are spatially arranged to take advantage of their intrinsic biological potential to accommodate to the edaphic dissimilarities of steep hillsides. Spatial arrangements of annual and perennial crops in natural geosequences are discussed, and suggestions are given on how spatial considerations can be matched to preferred crop mixes of trees, shrubs and grasses, in an attempt to halt erosion and better protect the environment. Land use planning on a physiographic and soil capability basis is proposed, but acknowledges that effective implementation is subject to a determined campaign to extend both the theory of sound land management and the provision of technical assistance to peasants to demonstrate the concepts and to interpret the results of the practices. This paper explores certain aspects of physiographic and edaphic similarities and constraints of peasant farming practices on steep slopes, and offers some theoretical bases upon which hedgerow technology can be applied to improve water and plant relations, ameliorate environmental effects and be initiated by individual farmers at little cost. A range of other soil conservation or agroforestry techniques, as used in Haiti is described; and a simple monitoring or measurement model to determine the amount of soil saved is provided, and the possibility of teaching the methods to minimally trained field technicians is explored, pursuant to encouraging farmers to give greater attention to the value of soil conservation and proper land use planning.

Does global change threaten the world food supply

Abstract: The worlds agricultural system which was strengthened by the Green Revolution is now beginning to decline in total fertility. In 70% of developing countries population growth is outstripped food production. The causes turn out to be the old solution of the Green revolution itself. Irrigation is draining lakes and ground water as well as poisoning the soil with salt. Pesticides are becoming increasingly ineffective as pests evolve and adapt. Fertilizer use is increasing as yields are going down. Almost 80 million metric tons of nitrogen were used last year worldwide. A reliance on a few high yielding strains of corn wheat and rice allowed pests and disease to wipe out large amounts of food quickly. The potato fields of Mexico are being ravaged by potato viruses and the rice paddies of Asia are suffering from stagnation. A further complication is the unknown effect of global warming. It is predicted that droughts will increase in areas already suffering from lack of water. Farming practices are also a significant contributing factor as they lead to soil erosion. It is estimated that we lose 24 billion tons of top soil annually. This despite the fact that farmers are expected to feed an additional 90 million people annually. Population growth has also affected farming practices. The increased food supply in fertile regions caused rapid population growth in the same areas. As these new people spread across the land in search of shelter they displaced fertile farm land. This in turn pushed the farmers into marginal land were the cycle of erosion is repeated. The solution to this problem appears to lie in sustainable agriculture. This method relies on more biodiversity less chemical input and better land management policies aimed at water conservation and soil retention. Unfortunately the money needed to develop and perfect these technics are not being spent by the worlds governments.

Changes in Soil Profile Development and Nutrient Status due to the Afforestation of Agricultural Land

Abstract: Leth, Susanne & Breuning-Madsen, Henrik: Changes in Soil Profile Development and Nutrient Status due to the Afforestation of Agricultural Land. Geografisk Tidsskrift 92:70–74. Copenhagen 1992. In the middle of the last century, the recultivation of western Jutland began, and much of the former heathland was converted into agricultural land. Some of this land was too poor to guarantee stable plant production and satisfactory yields. Such land could be defined as marginal land. Consequently, it was abandoned at the beginning of this century and afforested with the conifer species Picea abies. In order to investigate the resultant changes in soil morphology and soil nutrients, a comparison was made of soils that had developed on land afforested with Picea abies at different times during this century, as well as those that had developed on adjacent agricultural land.