SHARMA, J.C.KHONGJEE, SHEMBHALANG2017-01-102017-01-10201247835http://krishikosh.egranth.ac.in/handle/1/95257ABSTRACT The investigations entitled “Runoff and nutrient losses under different landuses in Ga3a micro-watershed of Giri river in Solan district of Himachal Pradesh” was carried out with a view to ascertain the hydrological, physical and chemical properties, erodibility characteristics and soil and nutrient losses under different landuses viz. Agriculture, Orchard, Agrisilvihorti and Scrub. On the basis of detailed survey and random sampling, total 24 soil samples were collected from two depths i.e. 0.0-0.15 and 0.15-0.30 m. Soils were evaluated for their hydraulic, physical and chemical properties and erodibility indices, under different landuses. Interrelationship was worked out between some soil properties and erodibility indices, under different landuses. Results revealed that the soils of Ga3a micro-watershed were coarse in texture with sand constituting the major fraction. Soils were characterised by high bulk density, poor in moisture retention and had low available water. Soil reaction was found neutral under all the landuses. Among the landuses, orchard and agrisilvihorti lands were found to have higher organic carbon. Fertility status of the soils indicated that these were poor in available N, high in available P and low to medium in available K status. According to the erodibility indices based on empirical equations i.e. ER and EI, all the soils were found to be erodible, however, orchard and agrisilvihorti lands recorded lowest for the indices. ER and EI were found to be positively and significantly correlated with each other and can used interchangeably. Erodibility indices, based on WSA (>0.25mm) and MWD, predicted that among all the landuses, orchard and agrisilvihorti lands were least erodible as compared to other landuses. The results were also supported by the findings of runoff plot studies, and orchard soils were found to be more stable followed by agrisilvihorti, scrub and agricultural lands. The runoff (24, 22, 20 and 17 ha m x 10-3) and soil loss (44.4, 34, 24 and 18.6 tonnes ha-1 x 10-2) were observed under agriculture, scrub, agrisilvihorti and orchard land use, respectively. Maximum loss of NO3-N, available P and K (86.6, 16.8 and 64.2 kg ha-1, respectively) was also recorded under agricultural land use. The results led to conclusion that orchard and agrisilvihorti lands protected the soil against impact of falling rain drops, encouraged infiltration, reduced the surface runoff, consequently retained rainwater on soil surface for longer time, bound the soil mechanically and improved the physical and chemical properties of the soil. The study further indicates that there is an urgent need to put more and more area under agronomic measures to check the runoff, soil erosion and nutrient losses. There is a need to adopt suitable soil and water conservation measures in agricultural and orchard lands to sustain their health for sustaining the crop production by checking soil and nutrient losses. Scrub lands need to be replaced by more effective soil and water resource conserving systems like agro-forestry, agri-horticulture, silvi-pasture.enThesis