MSc

The study titled ‘Zinc biofortification for enhancing yield and quality of yard long bean (Vigna unguiculata subsp. sesquipedalis (L.) Verdcourt) in ferralitic soils’ has been carried out at the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani during 2013-14. The above investigation was under taken to study the effect of zinc biofortification through mineral fertilization on pod yield and quality of yard long bean and bioavailability of zinc.

The experiment was laid out in Instructional Farm, Vellayani in Randomized Block Design with ten treatments and three replications during October, 2013 to January, 2014. The treatments included two methods of Zn fertilizer application viz., soil application of Zn @ 2.5 kg ha-1 and 5 kg ha-1 and foliar application of ZnSO4 @ 0.025 per cent and 0.05 per cent along with Package of Practices Recommendations of KAU (POP) and Soil Test Based Recommendations (STBR).

The treatment effect was statistically not significant for the biometric characteristics of yard long bean. Regarding the pod yield, foliar application of ZnSO4 @ 0.05 per cent along with STBR (T10) recorded the highest yield per plant. The same treatment showed the highest value for single pod weight plant-1 and number of seeds pod-1as well as B:C ratio and total dry matter production. However, the harvest index was highest for the T5 (POP + ZnSO4 foliar @ 0.025 %) which on par with all other treatments except T1 (POP).

The results of the soil analysis at the time of final harvest revealed a general increase in available nutrient content compared to that of initial status. The soil application of Zn @ 5 kg ha-1 along with POP (T4) recorded the highest value for available Zn followed by the treatment with STBR + Zn @ 5 kg ha-1 (T8).

The chemical analysis of pods revealed that, foliar application of ZnSO4 @ 0.05 per cent along with STBR (T10) recorded the highest concentration of Zn and lowest value for phytate. The increase in Zn content was 41.47 per cent over its counterpart without Zn application. The same treatment (T10) showed the lowest phytate P: Zn ratio indicating highest bioavailability of Zn. The performance of treatment T1 (POP) was comparatively poor in these aspects. The Zn content of bhusa showed a different pattern with POP based treatments receiving foliar application of Zn showed highest values.

Evaluating the performance on methods and levels of Zn application for biofortification in yard long bean var. Vellayani Jyothika, it was observed that, the treatment receiving STBR based N, P and K fertilizers along with 0.05 per cent ZnSO4 foliar spray at branching and flowering stages (T10) recorded the highest pod yield, B:C ratio and Zn content with lowest values for phytate and phytate: Zn ratio. Considering the lowest nutrient input addition and more benefit, the same was found to be the best treatment. However, the treatment receiving POP based N, P and K recommendation with Zn as foliar treatment at 0.05% (T6) was also found to be equally effective in all aspects with slightly lesser values but statistically on par with the above.

The foliar application of ZnSO4 @ 0.05 per cent to yard long bean at branching and flowering stages was able to increase pod yield and zinc density and can reduce the phytate content of pods, both at POP and STBR based treatments of N, P and K fertilizers. Hence it can be concluded that whatever be the rate of application for N, P and K, i.e. either POP or soil test based recommendation, the foliar application of ZnSO4 @ 0.05 per cent at branching and flowering stages was found to be the best as regards to pod yield, Zn content and quality compared to other methods and rate of zinc application.