Pattern of root activity in bananas under irrigated and rainfed conditions

Abstract

The experiments were undertaken with an objective to find out the most active root zone of banana var. ‘Nendran’ employing radioactive 32p. These were conducted in the College of Horticulture, Kerala Agricultural University, Vellanikkara, during the year 1983-84. The field experiments were laid out in randomised block design, with three replications and the plants were raised under normal conditions.

While taking into consideration the number, length and diameter fresh and dry weights of roots, all these were found to be more for the rainfed crop than the irrigated. This explains the enhanced production of roots under conditions of moisture stress.

The radioactivity was injected at four months ago of the plant. The area around each experimental plant was injected with 32p solution with the help of a dispensette. The different lateral distances used for the 32p injection were 20cm, 40cm, 80cm and 120 cm and the different depths were 5cm, 15 cm , 30cm and 60cm. The third leaf was radio assayed and the 32p counts were used for finding out the percentage of active roots at the various treatment sites.

The results of radiotracer studies indicated that maximum percentage of active roots was located at a soil zone covering 20cm distance and 30 cm depth from the base of the plant under irrigated condition, at five and six months age of the plant. The rainfed crop had its maximum percentage of active roots at a soil zone of 30cm deep and 40cm away from the plant. As the lateral distances increased from 20cm to 120cm, a reduction was noticed in the percentage activity of roots accordingly, under both irrigated and unirrigated conditions. But the root activity was not significantly different at different depths for the irrigated crop, which was significant for the rainfed crop.

Under high moisture stress roots tend to forage into deeper layers of soil for getting the available water. Hence deeper soil zones had more active roots under unirrigated conditions, compared to irrigated crop, which had more surface active roots.

An experiment was also organized to study of the translocation of absorbed 32p to various parts of the plant after flowering under irrigated condition. It was observed that male flowers had maximum concentration of 32p followed by female flowers or fruits. Of the various leaves, topmost younger leaves were found to build up more 32p than matured leaves, indicating a translocation to the developing immature leaves.