Sub- theme - V SUSTAINABLE USE OF LAND RESOURCES

Sub-theme: V

SUSTAINABLE USE OF LAND RESOURCES

Laws Change; people die; the land remains.
-Abraham Lincoln

The world’s land resources that include soil, water and vegetation are under great pressure to meet the food, fiber and housing needs of ever growing population. In addition, the land resources are also expected to provide services related to biodiversity, clean water and air and swallow vast amount of wastes produced by living beings. In nature different processes within the earth’s surface generally occur in a cyclic manner thus maintaining a balance between different components of the ecosystems. For example, carbon cycles between soil, vegetation, ocean and atmosphere. However, human intervention through industrial activities and change of land use has perturbed the carbon cycle leading to increased carbon dioxide concentration in
the atmosphere. Not only air, human activities have also resulted in degradation of soil and water resources. Land degradation has threatened the livelihood of millions of people and future food security. Therefore, the greatest challenge before us today is to manage the land resources in a sustainable manner so that these are maintained without degradation for present and future generations
Major uses of land resource include forestry, pasture and grasslands, agriculture, housing and urban and industrial activities. The guiding principle for sustainable land management depends on ecological and economic interrelationships. The choice of land use and the practices for its sustainable management are site-specific and depend on local needs of the population. Soil is an important natural resource and its sustainable use is generally linked to agricultural management, though it performs multifarious functions. In relation to sustainable management one needs to know how agricultural management practices are influencing soil physical, chemical and biological parameters. Soil organic matter is considered a key constituent that influences most of the soil properties and governs the capacity of soil to perform ecosystem functions. The term soil organic matter is generally used to represent the organic constituents in the soil, including un-decayed plant and animal debris, their partially and completely decomposed products, and the soil microbial biomass. Soil organic matter, generally determined as organic carbon is taken as an index of soil fertility and crop productivity. Several factors, such as rainfall, temperature, vegetation and soil type determine the amount of carbon in soil. Due to land use changes such as deforestation, conversion of grasslands to agricultural land etc. soils have lost considerable amount of organic carbon. These losses of organic carbon from soils that are already of low fertility are clearly of concern in relation to future productivity. Sustainable management of soil requires that organic matter be maintained at an optimum level governed by soil characteristics and climatic conditions. Management practices or technologies that enhance carbon input to soil and decrease output/decomposition of carbon lead to net carbon storage in soils. Sources of carbon input include the amount of above ground and below ground biomass returned to the soil, and addition of bio-solids such as animal manure, compost, sludge etc. Technologies for enhancing carbon input to soil include i) intensification of agriculture ii) increasing area under forests, and iii) agro-forestry. Agricultural intensification implies adoption of recommended management practices on prime agricultural soils while restoring degraded and marginal soils to productive land uses.

Management options that contribute to reduced decomposition or losses of carbon from the soil include conservation agriculture, reduced or no-tillage practices, mulch farming, and reducing bare fallow or increased cropping intensity. Croplands under no-till systems have been shown to increase soil C compared to more intensive tillage operations. In some climatic regions, land dedicated to annual crops can be planted with a grass or legume cover crop after harvesting the cash crop to protect the soil during fallow period. This increases the residue inputs to the soil and hence soil carbon storage. Deforestation of land


For providing sustainable fertilizer management practices to increase crop productivity and minimize environmental pollution, soil testing has an essential role. The basic aim of the soil-testing is to provide recommendations to the farmers for economic and balanced use of fertilizers. Soil testing involves the analysis of soil samples in the laboratory for estimating plant available nutrient status of soil. Based on soil test values, the soils are categorized as low, medium and high in supplying nitrogen, phosphorous and potassium to a growing crop. Analysis of other nutrients can also be carried out for diagnosing nutrient deficiencies. Fertilizer application based on soil testing usually leads to an increase in yields and profits by providing the correct and balanced amounts of nutrients. Without soil test based fertilizer recommendation, a farmer may apply excessive or inadequate amount of nutrient(s) required for optimum plant growth. This not only means an uneconomical use of fertilizers, but in some cases crop yields may be reduced and any excess application of fertilizer may also degrade the soil and groundwater. Besides fertilizer recommendations, soil testing also provides information on soil reaction (pH) and salt status (estimated from electrical conductivity) of the soil, which could be used to estimate lime or gypsum requirement for soil reclamation.

Water is another important natural resource that is becoming scarce day by day. It is not only the quantity but also the quality of water that is of concern. There is no single measure that constitutes good water quality since it depends upon several parameters. In some cases groundwater can be contaminated with chemicals or bacteria. Water quality is defined by analyzing it in terms of its i) chemical content such as hardness (calcium + magnesium), metals (iron etc), nutrients (nitrogen and phosphorus), chloride, sodium, organic compounds, etc. ii) physical content such as turbidity, color, odour, etc. and iii) biological content such as coliform, viruses, etc. Good quality (potable) drinking water is free from disease-causing organisms, harmful chemical substances and radioactive matter, tastes good, is aesthetically appealing and is free from objectionable color or odour. In India, the Central Pollution Control Board has identified water quality requirements in terms of a few chemical characteristics, known as primary water quality criteria. Further, Bureau of Indian Standards has also recommended water quality parameters for different uses.

There are different guidelines to evaluate quality of water for irrigation purposes. Based on electrical conductivity, sodium adsorption ratio and residual sodium carbonate irrigation water is categorized into different classes. Sustainable use of marginal quality groundwater is determined by soil characteristics, crop to be grown and the availability of good quality surface water for conjunctive use. In agriculture huge amounts of water are used for irrigation purposes especially for crops like paddy. This seriously impacts the aquifer and the availability of groundwater. Practices/technologies have been devised for efficient management of irrigation water. Some on-farm practices for efficient water management include weather based irrigation schedules, drip irrigation, soil matric potential based irrigation, bunding the field to check run-off and precise laser leveling of the field etc. Other practices include brick-lining of the irrigation channels, rain-water harvesting and groundwater recharge.