SEDIMENT OUTFLOW FROM PADDY MULCH AT VARYING LAND SLOPES UN- DER SIMULATED RAINFALL CONDITIONS Sachin Kumar Singh*and P. S. Kashyap Department of Soil and Water Conservation Engineering, College of Technology, G.B. Pant University of Agriculture and Technology, Pantnagar-263145 (U.S. Nagar, Uttarakhand) India *Corresponding Author's E-mail : sachinkumar88gzb@gmail.com ABSTRACT : Soil erosion in India is really need of hour as to improve soil health is on main agenda. Various measures are used by researchers to reduce soil loss due to runoff and best one is found to be biological measures. In biological measures, organic mulches are very effective in preventing soil erosion, to reduce sediment transport rate, runoff and increasing infiltration. The study was carried out with the objectives to observe the sediment outflow during paddy mulch treatments at selected land slopes with different rainfall intensities under simulated rainfall conditions, just to count soil loss. The quantity of mulch was taken as, 6 ton/ha, 8 ton/ha and 10 ton/ha and for each mulch treatment, three rainfall intensities viz. 11cm/h, 13cm/h and 14.65cm/h at 0%, 2% and 4% land slopes were selected. The average sediment concentration and outflow was found to be increasing with the increase in land slope, but sediment concentration and outflow decreased with increasing mulch rate for particular land slope and rainfall intensity. The sediment outflow rate for no mulch treated land was higher as compared to paddy straw mulch treated lands. Mathematical relationships were developed for relating sediment outflow rate, sediment concentration, land slope and rainfall intensity for a particular mulch treatment. It was observed that values of sediment outflow rate and average sediment concentration had a good correlation with rainfall intensity and land slope for each mulch treatment. The correlation coefficients of developed models were found to be more than 90% which supports mulching as the best biological measure. Keywords : Paddy mulch, sediment outflow, land slope, simulated rainfall. Soil erosion and sediment outflow from agricultural lands isquiet serious global problem (Wolancho, 19). The soil resources of the world are finite, functionally non-renewable and prone to different forms of degradation due to over-exploitation and faulty management practices. Topsoil erosion is a global problem that causes environmental pollution of waterways and loss of soil fertility (Cerdà et al., 1, 2 and 3). Soil degradation has reached alarming proportions in many parts of the world, especially in the tropics and sub-tropics regions. Soil erosion caused by water is a major factor contributing to land degradation in India. The estimates suggest that globally about 24 billion tonns of soil is lost annually through water erosion while formation of natural rate of soil regeneration is less. In India, the problem of soil erosion is quite serious as about 18.5% of the world total soil erosion occurs here. India loses about 16.4 t of soil/ha/yr, of which 29% is lost permanently into the sea, 10% gets deposited in the reservoirs reducing their capacity by 1–2% every year and the remaining 61% gets displaced from one place to another (Dhruvanarayana, 4). There are several stages or type of water erosion including splash, sheet, inter-rill, rill, gully and stream bank erosion. These processes are governed by a large number of variablesfactors pertaining to rainfall, soil system, land topography, crop cover condition and management practices (Wischmrier and Smith, 18). The sediment generation is governed by the erosivity of erosive agents and the erodibility of the soil system, while the transportation process is mainly influenced by the transport capacity of runoff. Erosion by water is prime cause while that in form of rainfall and runoff becomes erosive agents, because rainfall energy is expanded in detaching soil particles and transportability of the sediment depends upon its velocity of runoff. The top layer of soil provides nutrients and a physically and biologically environment important to plant growth. So it is important to reduce the rate of soil erosion by use of crop and cover condition. The vegetation on surface helps in controlling the kinetic energy of falling raindrops, binding the soil particles and binding soil material by the root system which resists the detachment of soil aggregates (Wischmeier and Smith, 18). Change soil and water behaviour HortFlora Research Spectrum www.hortflorajournal.com Vol. 5, Issue 4; 275-283 (December 2016) ISSN: 2250-2823 Article’s History: Received : 22-11-2016 Accepted : 12-12-2016