RELATIVE EFFICIENCY OF AZOLLA AND OTHER ORGANIC MANURES IN SUMMER RICE (ORYZA-SATIVA)

A field study was conducted during 2 dry seasons (December-May) of 198 4-85 and 1985-86 at Kalyani, to find out the effect of Azolla, blue-gr een algae and other organic matters on 'Jaya' rice (Oryza sativa L). I ncorporation of Azolla, Ipomoea carnea Jacq., farmyard manure, Pistia sp and water hyacinth [Eichhornia crassipes (C. Martius) Solms-Laub.] significantly increased the grain and straw yields of rice compared wi th the control. Dual cropping of Azolla and inoculation with blue-gree n algae were at par with the control. Basal dressing of Azolla was sup erior to its top-dressing and dual cropping. Application of Azolla @ 1 0 tonnes/ha + 90 kg N/ha (in 3 splits) gave the highest grain yield of 8.8 tonnes/ha. The extent of yield increase in different treatments c ompared with the control was 4.07-102.3%. The response in grain yield on application of 10 tonnes/ha Azolla was equivalent to that of 60 kg N/ba. Use of Ipomoea sp as green-leaf manure proved more efficient tha n of Azolla. The efficiency of Azolla was either equal to or more than those of farmyard manure, water hyacinth and Pistia sp. The residual N status of soil depended on the uptake of N by the plants as well as addition through Azolla and other manures.