Water retention characteristics of soil bio-amendments used as growing media in pot culture

The effi cacy of the natural bio-amendments in improving physical condition as well as water retention characteristics of the growing media in pot culture was studied on ten different compositions of growing media. The treatments comprised of (i) soil as sole medium; (ii) soil + sewage sludge (SS) in the ratio of 1:1; (iii) soil + SS + coir (CP) in the ratio of 1:1:1; (iv) soil + vermicompost (VC) in the ratio of 1:1; (v) soil + VC + CP in the ratio of 1:1:1; (vi) soil + farmyard manure (FYM) in the ratio of 1:1; (vii) soil + FYM + CP in the ratio of 1:1:1; (viii) soil + SS + VC in the ratio of 1:1:1; (ix) soil + SS + FYM in the ratio of 1:1:1 and (x) soil + FYM + VC in the ratio of 1:1:1. The bulk density of media composition soil+SS+CP, soil+VC+CP and soil+FYM+CP was 24.2, 27.5 and 27.5% lower than the media containing only soils (1.32 mg m-3), respectively. The water holding capacity (WHC) was lowest (45.4%) in sole soil treatment and it was 6.3, 5.6 and 6.1 times higher in soil+SS+CP, soil+VC+CP and soil+FYM+CP, respectively. The volumetric water retention at various suctions was signifi cantly improved by addition of the organic amendments with soil. The magnitude of the differences in water retention among the treatments became wider at the higher suctions. The combination of soil+VC+CP showed the highest amount of water retention among all the treatments at all the suctions. The air fi lled porosity was highest (190.7%) in soil+FYM+CP media and lowest (25.3%) in sole soil media. Signifi cant increase in easily available water was observed with the incorporation of coir with sewage sludge, vermicompost and FYM. The water buffering capacity was lowest in media with only soil (7.56%) and the media containing soil+VC+CP recorded the highest (24.7%) water buffering capacity.