Abstract:
An experiment was conducted in the college of Agriculture, Vellayani during the period from July 1993 to January 1994 with the object of finding out the effect of nitrogen, phosphorus and potassium on seed production of gamba grass (Andropogon gayanus kunth).
The experiment was laid out in partially confounded factorial design with two replications and three blocks in each replication. The experimental treatments consisted of twenty seven combinations of three levels each of nitrogen (75, 150 and 225 kg/ha) phosphorus (50,75 and 100 kg/ha) and potassium (50, 75 and 100 kg/ha).
Increase in nitrogen levels results in increased plant height, number of tillers, number of leaves, fresh fodder yield and dry fodder yield. Phosphorus and potassium did not have any significant effect on these parameters, except dry fodder yield which was significantly reduced by potassium levels. Nitrogen content in the fodder was not influenced by either nitrogen or phosphorus or potassium. Phosphorus content in the fodder was increased by phosphorus application and potassium content was increased by potassium application.
Uptake of nitrogen was higher at higher levels of nitrogen while phoshorus and potassium did not have any influence. Uptake of phosphorus was increased by nitrogen and phosphorus while potassium caused a reduction in phosphorus uptake. Potassium uptake was significantly increased due to nitrogen application. Crude fibre content in the fodder was found to decrease with an increase in the levels of NPK nutrients. Nitrogen caused a significant increase in the number of panicles per plant, but reduced the number of seeds per panicle significantly.
Seed viability, seed germination and number of kernals /500 seeds were significantly increased by the levels of phosphorus while nitrogen and potassium showed no significant effect.
Seed purity, seed moisture and 1000 seed weight were not influenced by none of the treatments.
Maximum seed yield was recorded at the highest level of nitrogen, but neither nitrogen, nor phosphorus, nor potassium had any significant effect.
Nitrogen content of the soil was found to increase with nitrogen fertilization and phosphorus content by phosphorus fertilization. Potassium status was increased by nitrogen and potassium.
