AGR 105 Unit 3 1-3.pdf

UNIT – III SOIL PLANT WATER RELATIONSHIP  QUALITY OF IRRIGATION WATER  INTRODUCTION The suitability of irrigation water is mainly depends on the amounts and type of salts present in water. The main soluble constituents are calcium, magnesium, sodium as cations and chlo...

UNIT – III SOIL PLANT WATER RELATIONSHIP  QUALITY OF IRRIGATION WATER  INTRODUCTION The suitability of irrigation water is mainly depends on the amounts and type of salts present in water. The main soluble constituents are calcium, magnesium, sodium as cations and chloride, sulphate, bi carbonate as anions. The other ions are present in minute quantities are boron, selenium, molybdenum and fluorine which are harmful to animals fed on plants grown with excess concentration of these ions.  CRITERIA TO DETERMINE THE QUALITY OF IRRIGATION WATER The criteria for judging the quality of irrigation water are: Total salt concentration as measured by electrical conductivity Relative proportion of sodium to other cations as expressed by sodium adsorption ratio Bicarbonate content, boron concentration and soluble sodium percentage.  TOTAL SOLUBLE SALTS Salinity of water refers to concentration of total soluble salts in it. It is the most important single criterion of irrigation water quality. The harmful effects increase with increase in total salt concentration. The concentration of soluble salts in water is indirectly measured by its electrical conductivity (ECw). The quality of saline waters has been divided into five classes as per USDA (United States Department of Agriculture) classification given in Table. Adverse effects of saline water include salt accumulation, decreased water availability to plants, poor germination, patchy crop stand, stunted growth with smaller, thicker and dark green leaves, leaf necrosis (premature death of plant cells due to injury) & leaf drop, root death, wilting of plants, nutrient deficiency symptoms and poor crop yields.  Medium range of Salinity class of irrigation water is ____ milli mhos/cm A. 5 D.