Ecology and production of Salvinia natans Hoffim; in Kashmir

Summary Ecological problems arising as a result of rapid growth of S. natans Hoffim in some lakes of Kashmir have been studied. High viability of spores coupled with rapid vegetative propagation seem to be responsible for the spread of the weed. Lake channels protected from wind by a canopy of trees are the most favourable situations in which Salvinia produces a thick mat. Water in these channels is rich in nutrients. Oxygen poor layers of water beneath the mat are detrimental for insect and fish life. Besides, the changing light conditions have profound influence on the submerged vegetation. The most common associates of Salvinia are Hydrocharis dubia and Ceratophyllum demersum.Maximum plant biomass is recorded during August–September with higher efficiency at partially shaded sites. Correlation exists between caloric values and dry matter production and between caloric value and per cent organic carbon.Under laboratory conditions, water of a pH between 4.6–6.0, sodium chloride concentrations higher than 1 % and continuous submergence under water are harmful to the growth of the weed. Partial shady situations seem to be quite beneficial for the growth. Harvesting would probably be the most economical method of control.