M Sc

An experiment entitled “Zinc fertifortification of rice (Oryza sativa L.) cultivars”
was conducted during 2019-2021 at College of Agriculture, Vellayani. The main
objective of the study was to enhance the grain Zn content of rice cultivars through Zn
fertilization. The field experiment was carried out in farmer’s field at Southern Coastal
Plain (AEU 1) during the kharif season 2020-21. The field experiment was laid out in
Randomised Block Design (with two factors) and was replicated thrice. The treatment
combinations included four medium duration rice varieties viz., Uma (V1), Pournami
(V2), Gouri (V3), DRR Dhan 45 (V4) and four foliar Zn fertilization viz., without ZnSO4
(F1), ZnSO4 @ 0.1 per cent at maximum tillering (MT) and milk (M) stages (F2), ZnSO4
@ 0.5 per cent at MT and M stages (F3), ZnSO4 @ 1.0 per cent at MT and M stages (F4).
The growth parameters such as plant height, number of tillers per hill and dry
matter production at panicle initiation and harvest stages were significantly influenced by
foliar Zn fertilization. ZnSO4 @ 1.0 per cent (F4) recorded taller plants (80.5 and 113
cm), higher tillers per hill (20.2 and 15.7 nos.) and higher dry matter production (12.0 and
28.9 g hill-1
) at panicle initiation and harvest stages respectively, and were comparable
with ZnSO4 @ 0.5 per cent (F3). Higher leaf area index 3.87 recorded at panicle initiation
stage in ZnSO4 @ 1.0 per cent (F4) was comparable to ZnSO4 @ 0.5 per cent (F3).
Higher spikelets per panicle (120 nos.) and filled grains per panicle (78.0 nos.)
recorded in Uma (V1) were statistically similar to Pournami (V2). Sterility per cent (35.2)
and thousand grain weight (25.6 g) recorded in Uma (V1) was higher and comparable to
DRR Dhan 45 (V4). ZnSO4 @ 1.0 per cent (F4) recorded higher values for yield attributes
such as productive tillers per square meter (459 nos.), grain weight per panicle (2.37 g),
spikelets per panicle (119 nos.), filled grains per panicle (83.3 nos.), which were
comparable to ZnSO4 @ 0.5 per cent (F3).
Foliar fertilization with ZnSO4 @ 1.0 per cent (F4) produced higher grain 4.65 t
ha-1
and straw 4.85 t ha-1
yield, and was comparable to ZnSO4 @ 0.5 per cent (F3) which
recorded grain and straw yield of 4.62 and 4.81 t ha-1
respectively. The increase in grain
and straw yield due to ZnSO4 @ 0.5 per cent (F3) were 12.1 to 11.1 per cent respectively
over the control plot (without ZnSO4 ) (F1).
Biofortified rice variety DRR Dhan 45 (V4) recorded significantly higher Zn
content in rough rice (28.6 mg kg-1
) and its milled fractions viz., brown rice (33.7 mg kg1
), white rice (25.3 mg kg-1
), rice husk (51.1 mg kg -1
) and rice bran (97.7 mg kg-1
).
Significantly higher Zn content was recorded in boiled rice (16.6 mg kg-1
) and decanted
rice water (19.9 mg kg-1
) of variety DRR Dhan 45 (V4). As a variety with high Zn content
in rough rice and its milled fractions, Gouri (V3) was second only to DRR Dhan 45 (V4).
Among non biofortified rice varieties, lower Zn content in rough rice (18.8 mg kg-1
),
brown rice (16.3 mg kg-1
), white rice (12.2 mg kg-1
), rice husk (24.7 mg kg -1
) and rice
bran (47.1 mg kg-1
) was recorded in Uma (V1) and was comparable with Pournami (V2).
Lower Zn content recorded in boiled rice (8.0 mg kg-1
) and decanted rice water (9.6 mg
kg-1
) of variety Uma (V1) was comparable to Pournami (V2).
Foliar fertilization with ZnSO4 @ 1.0 per cent (F4) could increase Zn content in
rough rice (24.0 mg kg-1
), brown rice (28.3 mg kg-1
), white rice (21.2 mg kg-1
), rice bran
(82.0 mg kg-1
), boiled rice (13.9 mg kg-1
), decanted rice water (16.7 mg kg-1
). However, it
was comparable with ZnSO4 @ 0.5 per cent (F3) which recorded Zn content of 22.0, 26.0,
19.5, 75.3, 12.8 and 15.4 mg kg-1
in rough rice, brown rice, white rice, rice bran, boiled
rice, and decanted rice water respectively. Zn content in rice husk (54.6 mg kg-1
) was
significantly increased by ZnSO4 @ 1.0 per cent (F4).
NPK content of grain and straw was enhanced by ZnSO4 @ 1.0 per cent (F4)
resulting in higher plant uptake of NPK, which was comparable with ZnSO4 @ 0.5 per
cent (F3). Varieties DRR Dhan 45 (V4) and Uma (V1) resulted in Zn biofortification
recovery efficiency (ZnBRE) of 3.26 and 1.39 per cent respectively. Significantly higher
ZnBRE efficiency of 3.14 per cent was recorded in ZnSO4 @ 0.5 per cent (F3), ZnSO4 @
1.0 per cent (F4) recorded ZnBRE of 1.99 per cent.
Economic analysis revealed highest gross income (₹ 140474 ha-1
), net income (₹
46900 ha-1
) and benefit: cost ratio (1.50) in treatment combination non biofortified
variety Uma foliar fertilized with ZnSO4 @ 0.5 per cent (v1f3). Increasing the foliar
fertilized ZnSO4 from 0.5 per cent (v1f3) to 1.0 per cent (v1f4) in variety Uma could bring
about only negligible increase in gross income, net income and benefit: cost ratio by 0.5
per cent, 1.1 per cent and 0.3 per cent respectively. Biofortified variety DRR Dhan 45
foliar fertilized with ZnSO4 @ 0.5 per cent (v4f3) recorded gross income, net income and
benefit: cost ratio of ₹ 135753 ha-1
, ₹ 42019 ha-1
and 1.45 respectively. Increasing foliar
fertilization of ZnSO4 from 0.5 per cent to 1.0 per cent resulted in an increment in gross
income, net income and benefit: cost ratio by 1.2 per cent, 3.5 per cent and 0.7 per cent
respectively.
The present study indicated that foliar fertilization with ZnSO4 @ 0.5 per cent at
maximum tillering and milk stages as an economically viable option to significantly
increase grain and straw yield of rice, and also to increase Zn content in rough rice and its
milled fractions, resulting in increased Zn content in boiled rice and decanted rice water,
irrespective of the rice variety.