Short term influence of gypsum, farm manure and commercial humic acid on physical properties of salt affected soil in rice paddy system

Addition of organic materials to soil has been one of the most common practices to improve soil properties. Combined application of organic and inorganic amendments has been known to play a significant role in improvement of soil properties. A field experiment was conducted to explore the role of gypsum (G), farm manure (FM) and commercial humic acid (HA) on the improvement of physical properties of saline sodic soil. Different dosages of G, FM and HA were applied to soil under cultivation of rice crop. Organic carbon (OC) and organic carbon pool (OC pool) were increased up to 73 % and 71 %, respectively, with 100 % soil gypsum requirement (SGR) combined with 20 ton FM ha/sup -1/. There was 15.8 % increase in water stable aggregates (WSA) by 100 % SGR combined with 20 ton FM ha-1. Application of gypsum particularly with farm manure decreased bulk density from 1.66 to 1.33 Mg m/sup -3/ and increased total porosity (TP) by 24 %. HA did not improve any soil property with considerable results in current study. There was positive significant (P<= 0.05) correlation between OC and OC pool, WSA and TP (r= 0.98, 0.91, 0.66, respectively; P<= 0.05), while bulk density had negative correlations with all soil properties examined in our study. (author)