UPSC: Civil Service Exam 2009



Part – 1

1.Write short notes on any three of the following in about 200 words each:


 Tillage operations in various forms have been practiced from the very inception of growing plants. Primitive man used tools to disturb the soils for placing the seeds. The word tillage is derived from ‘Anglo-Saxon’ words Tilian and Teolian, meaning ‘to plough and prepare soil for seed to sow, to cultivate and to raise crops’. Jethrotull, who is considered as father of tillage suggested that thorough ploughing is necessary so as to make the soil into fine particles.

Tillage is the mechanical manipulation of soil with tools and implements for obtaining conditions ideal for seed germination, seedling establishment and growth of crops. Tilth is the physical condition of soil obtained out of tillage (or) it is the result of tillage. The tilth may be a coarse tilth, fine tilth or moderate tilth.

Objectives of tillage The main objectives of tillage are

  • To prepare a good seed bed which helps the germination of seeds.
  • To create conditions in the soil suited for better growth of crops.
  • To control the weeds effectively.
  • To make the soil capable for absorbing more rain water.
  • To mix up the manure and fertilizers uniformly in the soil.
  • To aerate the soil.
  • To provide adequate seed-soil contact to permit water flow to seed and seedling roots.
  • To remove the hard pan and to increase the soil depth.

To achieve these objectives, the soil is disturbed / opened up and turned over.
Types of tillage: Tillage operations may be grouped into
1. On season tillage
2. Off-season tillage

Tillage operations that are done for raising crops in the same season or at the onset of the crop season are known as on-season tillage. They may be preparatory cultivation and after cultivation.

Tillage operations done for conditioning the soil suitably for the forthcoming main season crop are called off-season tillage. Off season tillage may be, post harvest tillage, summer tillage, winter tillage and fallow tillage.

(b) Herbicide Residue Management

Herbicides are a group of organic compounds that possess far-reaching environmental consequences when persistent in the soil. A persistence problem arises when the herbicides are applied scrupulously or continuously; the crop failure necessitates replanting; a susceptible crop follows a short term crop which received a persistent herbicide; and the decomposition of the applied herbicide proceeds very slowly (Sankaran et al. 1993). The longer persistence of a herbicide poses a hazard to subsequent land use and is undesirable. Recent concerns of ground and surface water contamination by some of the herbicides has led to renewed interest on persistence and dissipation behavior of herbicides in the environment. Several monitoring programmes have also been implemented by different countries to check the environmental contamination and for ecological risk assessment of herbicides. However, the information on managing herbicide persistence in the soil saving the crop from those situations are limited.

Management of herbicide residues in soil can be done by these methods:

  • Integrated weed management
  • Ploughing or cultivating the land
  • Incorporation of herbicides
  • Crop rotation
  • Growing herbicide tolerant crops
  • Light irrigation after application
  • Site specific application using variable rate applicator
  • Enhancing the herbicide degradation
  • Nutrients addition
  • Bioaugmentation
  • Deactivation of herbicides by Addition of organic matter
  • Use of non-phytotoxic oil, adjuvants and surfactants
  • Use of adsorbents, protectants and antidotes
  • Biochar addition
  • Use of safeners
  • Reducing the availability of herbicides in soil
  • Use of optimum and reduced dose of herbicide
  • Use of herbicides in combination and split doses
  • Method and time of application
  • Alternative use of herbicides
  • Match rates to weed infestation levels and using suitable formulations
  • Removal from site of contamination

(c) Seed Dormancy

Seed dormancy is defined as a state in which seeds are prevented from germinating even under environmental conditions normally favorable for germination. These conditions are a complex combination of water, light, temperature, gasses, mechanical restrictions, seed coats, and hormone structures.

Causes of Seed Dormancy

  • Hard seed coat – These are impermeable to water, gases so restrict water uptake and oxygen exchange.
  • Immature embryo – Seeds with small and undeveloped embryos do not germinate.
  • Germination inhibitors – Seeds contain some chemical plant growth regulators, which inhibit seed germination.
  • Period after ripening – Some seeds have a period of ripening. Those seed germinate only after the completion of this period.

Methods of Breaking Dormancy

  • Scarification
  • Stratification
  • Using chemicals like KNO3 and Gibberellic acid

Advantages of Seed Dormancy:

  • Plant embryo survives during adverse conditions of weather, which are not favorable for growth(like winter).
  • Creation of a seed bank
  • Seed dormancy allows more time for widespread seed dispersal
  • In some cases of dormancy one year’s seeds do not germinate the same year, this improves species survival

(d) Mulching and cover crops

 Mulching is the use of organic materials (plastic mulch is expensive and non-biodegradable) to cover the soil, especially around plants to keep down evaporation and water loss, besides adding valuable nutrients to the soil as they decompose. Mulching is a regular process and does require some labour and plenty of organic material, but has excellent effects, including encouraging the growth of soil fauna such as earthworms, preventing soil erosion to some extent and weed control.

 A cover crop is a crop planted primarily to manage soil erosion, soil fertility, soil quality, water, weeds, pests, diseases, biodiversity and wildlife in an agroecosystem (Lu et al. 2000), an ecological system managed and largely shaped by humans across a range of intensities to produce food, feed, or fiber. Currently, not many countries are known for using the cover crop method.

 Cover crops are of interest in sustainable agriculture as many of them improve the sustainability of agroecosystem attributes and may also indirectly improve qualities of neighboring natural ecosystems. Farmers choose to grow and manage specific cover crop types based on their own needs and goals, influenced by the biological, environmental, social, cultural, and economic factors of the food system in which they operate.

 Cover cropping is normally carried out also with nitrogen-fixing crops that grow fast and require little or no inputs like water or additional manuring. While cover crops can yield some returns, they are mostly used for covering the soil in the fallow months, adding nitrogen to the soil, suppressing weeds, preventing soil erosion and later used as biomass or fodder. Velvet bean is an example, and it finds use as a fodder crop and biomass generator. Another useful cover crop is Dolichos lablab which is a source of fodder and food.