The damaged lands comprise of
1) Water logged soils
2) Salt affected areas
Remedial measures to reclaim each of soil comprise of Preventive and Curative measures:
1. Preventative measures to control damage to lands:
Lining of canals and distributaries: Water percolating from canals and distributaries contribute a great deal to sub soil causing a rise in soil water table. Lining of canals prevents percolation of water largely and is being taken in the new canals.
Pre-irrigation soils surveys: Soil surveys prior to irrigation are quite necessary to select proper types of soils for perennial crops where by the utilization of irrigation for crops is maximum and contribution to the sub is the least. It is therefore, helps a remedy.
Fixing limits for perennial: Sugar cane is the most important crop under the canals in Maharashtra where it has acquired almost semi aquatic habitat. It makes splendid growth, if liberally supplied with soil moisture and the irrigation generally inclined to give water even to the extent of over irrigation with the result that it raises the sub soil water table where the drainage is obstructed. In many places, the soil water makes its appearance just below the ground level or appears as free water at the surface. Medium soils to 8’’ in depth are not suitable for sugarcane unless artificially drained.
Introduction of Block System: In a Block system a supply of water is provided for carrying on irrigated agriculture under conditions through out a block for a period of years. Block areas are de metered areas for which water is sanctioned for a term of years and within which any crops may be grown in the mansoon and Rabi season, subject to the provision that no more than one third of area shall be under sugar cane. During the hot season only allowed i.e. 11/2 acres of other perennial equal to 1 acre of sugarcane. Under block system, water is guaranteed for 6 years. Cane blocks allow 1/3 area under sugarcane and 2/3 area under seasonal crops.
Volumetric Supply of Irrigation to Sugarcane Factory Areas: The volumetric basis consists of the quantity of water to which the factory is entitled. It is fixed on acre-inches basis/acre of sugarcane area guaranteed. The inch depth fixed was 124’’ measured at distribution head. The volumetric rate is Rs 124/ acre-inches. The sugar owners have a freedom to arrange their programmer of plantation, harvesting within the guaranteed area. This system of volumetric supply of water has resulted in economic use of water and effective measures to control water logging.
2. Curative Measures:
Surface and Sub Surface Drainage: On construction of drainage scheme the sub soil water level go down the damaged areas are dried up and are brought back to cultivation after adopting reclamation methods.
Intensive well irrigation to keep the sub soil water level water under check:Another effective measure to improve the damaged areas is to have a network of working wells in suitable locations. Well irrigation forms an alternative solution where drainage cannot be adopted at economic cost.
Reclamation Method to Bring the Fertility of Soils for Growing Normal Crops: In a sound system of management, good tilth deserves first consideration. Regulation of the depth of water table by careful application of water and the disposal of surplus water by efficient drainage, natural or artificial are the very primary needs in the management of soils with a view to preserving soil fertility permanently. Agriculture practices, governing the maintenance of optimum amounts of basic factors such as soil moisture control etc. are not attended to maintain good surface and sub surface drainage therefore becomes very essential.
Partly water logged and fully water logged areas can be reclaimed by lowering sub soil water table to more than 4’ by artificial drainage. Preliminary agricultural operations are carried out on drying of the surface soil. The following sequence of operations is generally followed, of damaged lands due to water logging.
Effect of Excess Water on Soil and Plant Growth / Effect of Poor Drainage on Crop and Soil:
Drainage is the removal of excess gravitational water from the soil by artificial means to enhance crop production. If this water is not removed from the soil, the water logged or poor drainage condition occurs. Due to such condition, the soil as well as crop and soil are explained as below
Soil Aeration: Proper aeration in the root zone is necessary for development of healthy growth. The water air ratio in the pores of root zone of crop is such that it will not affect the yield. The increase in water content in soil pores is filled and the oxygen supply is reduced.
Effects on Plant Growth and Root Development: The crops become stunted with yellowing of leaves when the soil si saturated. In excess water, the plants usually die because of root damage caused by reduced supply of oxygen and accumulation of carbon dioxide with the related effects on the soil plant relationship. The adverse effects are not from direct presence of excess water, because crops will not suffer even in total from direct presence of excess water, because crops will not suffer even in total water culture, if they can get air. the root growth in such cases is also poor due to lack of aeration and they tend to remain largely near the surface and be subject to wilting when the surface becomes dry and even through there may be enough moisture below.
Anaerobic conditions in soil:
Nitrification: Crops depend for their growth on an adequate supply of nitrogen in the form of nitrates. The process of nitrification is carried out by bacteria, which requires oxygen from air in soil pores for their activity. Under anaerobic condition, marsh gas and hydrogen are formed. These gases reduce the nitrates. The nitrogen so released, escapes into the atmosphere alone with the hydrogen or converted into some form in which it is not available to crops. Thus, the suspension of microbiological activity in water logged soils directly.