Volume 61, Issue 1
January 1965, pages 1-61
pp 1-6 January 1965
pp 7-11 January 1965
pp 12-24 January 1965
The results of studies extending for nearly three years on the fluctuation of the plankton crop and factors responsible for production are reported. The peak production occurs during the south-west monson months. The cycle of physical and chemical factors and their relationship to plankton production are discussed. Data for iron content, estimated for the first time for our waters, are presented. It is concluded that, in Indian waters, it is the physiological state of the floral elements that finally decides the magnitude of plankton production on which ultimately depends fish production.
pp 25-30 January 1965
A study of the transformation of applied nitrogen in submerged rice soils, using N15 tagged compounds is reported. A part of the nitrogen applied as (N15H4)2SO4 and N15H4Cl was immobilized within ten days of submergence, due to microbial immobilization and the proportion of this remained fairly constant for a seventy-five day period of submergence. Fraction of the tagged nitrogen recovered in the ammonium fraction decreased with incubation. Application of extraneous inorganic nitrogen appeared to stimulate the mineralization of soil organic nitrogen. About 23–24% of the applied nitrogen was not accounted for at the end of seventy-five days of incubation. This loss is attributed to the oxidation of ammonium nitrogen to the nitrate form in the surface layer of the soil with subsequent leaching and denitrification in the reduced sub-surface zone.
pp 31-38 January 1965
A study of the utilization of nitrogen from (N15H4)2SO4 by the rice plant in relation to time of application was made in pot culture. Results show that fractional application of nitrogen with two-third at planting followed by one-third top-dressed at the boot stage results in the highest recovery of fertilizer nitrogen as compared to full application at planting or split application with top-dressing at the tillering stage. The former treatment also gives significantly higher grain yield, which is due to the increase in the number of filled grains per panicle. Nitrogen absorbed from top-dressing is found to be translocated to the growing parts.
pp 39-48 January 1965
pp 49-61 January 1965
Anisops bouvieri is a very common insect predator in fish ponds. It feeds voraciously on fish fry, larvae and nymphs of other aquatic insects and different types of planktonic crustaceans. During periods of starvation it develops cannibalistic tendencies. Copulation and oviposition in this species have been dealt with in some detail and certain aspects of behaviour during moulting have also been described.
The relative growth of head width and body length has been studied and a mathematical relationship between the two variables is established. The relationship between head width and body length and number of instar has been investigated into and the validity of DeAbate’s formula in forecasting the head width and body length at a subsequent instar with the known initial values at the first instar was examined. Some deviation was noticed between the observed values and those calculated by DeAbate’s formula. Hence an improved formula which satisfactorily predicts the value of head width and body length of subsequent instars with the known initial value of the first instar has been derived. Age and fecundity relationship in this species has been examined.