MOHANA RAO, PGIRI SHASHANK REDDY, T2020-01-222020-01-222018http://krishikosh.egranth.ac.in/handle/1/5810141512D5763Present study entitled, “Assessment of groundwater quality for irrigation in East Godavari district of Andhra Pradesh” was under taken in East Godavari district. A total number of 632 groundwater samples from 59 mandals of East Godavari district were collected during pre and post-monsoon periods. Water reaction (pH) in irrigation waters of study area varied from 6.4-8.1 and 6.5-7.9, EC ranged from 0.2-49.0 dS m-1 and 0.1-23.0 dS m-1, SAR ranged from 0.144.2 and 0.1-25.1, RSC ranged from -100 to 14.0 me L-1 and -111.4 to 10.0 me L-1 during pre and post-monsoon seasons, respectively. Dominant cation was Na+ > Ca2+ > Mg2+> K+. Likewise, in case of anions, Cl- > HCO3- > SO42- > B during pre-monsoon season. Similarly, during the post-monsoon season water dominant cation was Na+ > Ca2+ > Mg2+ > K+ type waters and Cl- > HCO3- > SO42- > CO32- type water in respect of anions. In both pre and post-monsoon seasons in all mandals of East Godavari district majority of the underground water samples had pH between 6.5 to 7.5 and majority of the samples recorded under neutral class. Based on EC, maximum number of underground water samples had EC between 0.75 to 2.25 dS m-1 (C3) i.e. high salinity. Based on SAR classification, during the pre-monsoon season 93.7, 4.1, 1.6 and 0.6 per cent samples recorded under S1, S2, S3, and S4 classes, whereas, in post-monsoon season 94.6, 4.4, 0.9 and 0.0 per cent samples recorded under S1, S2, S3, and S4 classes, respectively. In both pre and post-monsoon seasons majority of the samples were found under S1 class i.e. low sodium hazard. Based on RSC classification, during the premonsoon season 83.2, 4.7 and 12.0 per cent samples recorded under A1, A2 and A3 classes, whereas in post-monsoon season 77.8, 8.5 and 13.6 per cent samples recorded under A1, A2 and A3 classes, respectively. In both pre and post-monsoon seasons majority of the samples found under A1 class i.e. RSC<1.25 me L-1. xviii As per CSSRI classification 62.3, 20.9, 4.1, 1.3, 4.1, 4.1 and 3.2 per cent of water samples in East Godavari district during pre-monsoon season were classified under good, marginally saline, saline, high SAR saline, marginally alkali, alkali and high alkali categories, respectively. Likewise, during the post-monsoon 73.1, 11.7, 1.9, 0.9, 3.5, 5.4 and 3.5 per cent of waters were classified under good, marginally saline, saline, high SAR saline, marginally alkali, alkali and high alkali categories, respectively. In both pre and post-monsoon seasons majority of the samples were recorded under good category. As per USSL (1954) classification 0.9, 17.7, 55.4, 19.6, 3.8, 1.9 and 0.6 per cent of waters in East Godavari district during pre-monsoon season were classified under C1-S1, C2-S1, C3-S1, C4-S1, C4-S2, C4-S3 and C4-S4 categories, respectively. Likewise, during the post-monsoon 2.2, 27.2, 54.4, 1.6, 11.1, 2.2 and 1.3 per cent of water samples were classified under C1-S1, C2-S1, C3-S1, C3-S2, C4-S1, C4S2 and C4-S3 categories, respectively. In both pre and post-monsoon seasons majority of the samples recorded under C3-S1 category i.e. high salinity-low sodium hazard class. The yield of rice crop was negatively correlated with pH, but not at significant level whereas, it was negatively correlated with EC, Na+, and Cl- at one per cent level of significance, Boron and Ca+2-, were positively correlated at one percent level of significance and HCO3-, K+ and SO4-2 were positively correlated but not at signiciant level. It is observed that indiscriminate use of fertilizers for agriculture and sea water intrusions were contributed to higher concentration of some ions like Na+ and Mg2+ in irrigation water. Since majority of the groundwaters indicated high salinity and low sodium hazard ultimately result in reduced crop yield and lowering of net profit. Therefore, salt tolerant crops may be grown in salt affected areasen-USnullThesis