MSc

The investigation entitled “Stress induced source-sink modulation in yard long bean (Vigna unguiculata subsp. sesquipedalis (L.) Verdcourt)” was carried out during January to May, 2014 at the Instructional Farm, College of Agriculture, Vellayani, Kerala. The objective was to assess the influence of moisture- nutrient stress and foliar nutrition on source-sink relationship, productivity and profitability of yard long bean.
The experiment was laid out in split plot design with four replications. The main plot treatments included four different levels of irrigation viz., daily irrigation at 10 mm depth (I1), irrigation in alternate days (I2), irrigation once in 3 days (I3) and irrigation once in 3 days up to flowering and then in alternate days (I4) each at 20 mm depth. Combinations of nitrogen levels [recommended N (N0) and 25 per cent less of recommended N (N1)] and method of application [soil application of N and K in 4 splits (M1) and soil application of one-third N and K as basal followed by foliar application of 13:0:45 @ 0.5 per cent at fortnightly interval (M2)] formed the sub plot treatments. The adhoc recommendation for yard long bean (30:30:20 kg NPK ha-1) was adopted for this study. Farm yard manure @ 20 t ha-1 and full P were applied as basal dose, uniformly for all treatments.
Daily irrigation at 10 mm depth recorded significantly higher values for growth parameters viz., functional leaves plant per plant and leaf area index (1.56). Chlorophyll content of leaves at flowering (1.47 mg g-1), crude protein content and N and P uptake were also superior in daily irrigated treatments. K uptake was found to be the maximum in irrigation once in three days and it was on par with daily irrigation. The major yield attributes like number of pods per plant and pod yield per plant and total pod yield were not influenced by levels of irrigation. A better source : sink ratio (0.75) was registered in I3 (irrigation once in three days at 20 mm depth) while, the harvest index was higher for I3 and I4. The water use efficiency and water productivity (14.58 and 6.84 kg ha.mm-1) were
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found to be significantly superior in irrigation once in three days. Increasing the irrigation interval enhanced the proline accumulation in leaves and crude fibre in pods.
Application of recommended dose (RD) of nitrogen registered significantly higher values for functional leaves at later crop growth and leaf area index. Leaf chlorophyll content was found to be superior in N0 while, proline content (2.57 μ mols g-1) was higher in N1. Uptake of N and K were superior in RD N. Reducing the nitrogen levels to 75 per cent of RD did not cause any reduction in yield attributes and yield. Lower source : sink ratio and higher P uptake were noted in application of 25 per cent less of RD N. Recommended dose of N registered the highest value of water productivity, whereas WUE was the highest at 25 per cent less RD N.
Soil application of nutrients registered significantly higher yield (100.03 q ha-1) and uptake of nutrients over soil + foliar application. The biochemical characters viz., chlorophyll content and proline content were higher in soil + foliar application. The source : sink ratio and harvest index were favourably influenced by soil application of nutrients. WUE and water productivity (11.95 and 5.82 kg ha.mm-1 respectively) were superior in soil application of nutrients.
Irrigation once in three days at 20 mm depth registered the highest B : C ratio. Among the methods of application, soil application was found more economical.
From the study it could be inferred that daily irrigation is not necessary for yard long bean. Irrigation once in three days at 20 mm depth along with application of 25 per cent less of RD N (22.5 kg N ha-1) registered favourable source : sink ratio (0.70) and enhanced the B:C ratio (3.89). Soil application of nutrients recorded 10.25 per cent increase in yield and 15 per cent increase in B : C ratio compared to soil + foliar application.