| dc.description.abstract | Biofortification of staples with micronutrients and agronomic management practices such
as amounts, timing, placement and forms of fertilizers applied in production of these
crops have the potential to influence their grain micronutrient density. It has been
hypothesized that the amount of iron and zinc in grain can be increased through
agronomic management (fertilization practices) and plant breeding. However,
comprehensive agronomic approaches, including specific fertilization strategies with
macronutrients and micronutrients aimed at enhancing grain mineral concentration for
grain destined for human consumption are not well known, hence this work.
The objectives of this study were to determine the effect of N, P, K, liming, Fe and Zn
fertilization on grain yield, seed iron and zinc concentration in beans and to identify bean
genotypes with high seed Fe and Zn concentration grown under four environmental
conditions in Kenya. Six trials were conducted at four locations in Kenya (Kabete Field
16, Kabete Field 10, Thika and Kakamega) over two seasons. Treatments were four
levels ofN (0, 50, 100, 150 kg N ha-1
), P (0, 25, 50, 75 kg P ha'), K (0,50,100,150 kg
K ha-1
) and lime (0, 7, 14,21 t ha'). Fe was applied in soil (0, 2, 4, 6 kg ha") using Fe-
EDDHA (6% Fe) and foliar (0, 75, 150, 300 litres ha") using 0.2% FeS04 while Zn was
applied at 0, 2, 4 and 6 kg ha' into the soil using ZnS04 and as a foliar feed at 0, 50,
100 and 150 litres ha-I using 0.2% ZnS04. Calcium ammonium nitrate (CAN), triple
super phosphate (TSP), potassium sulphate (K2S04), agricultural lime (CaC03), Fe
EDDHA (Ethylene diamine di (O-hydroxy-phenyl acetic acid), ferrous sulphate (FeS04),
and zinc sulphate (ZnS04) were used as nutrient sources. In each trial, the experiment
was laid out in a split-plot design with three replicates. Nutrient levels were the main
plots and varieties were the subplots. The bean genotypes used were nine micronutrient
dense lines (AND 620, MLB 49-98A, VNB 81010, Maharagi Soja, GLP 2, TY 3396-12,
Gofta, Roba-l, and Nakaja) and a low nutrient dense variety (M211) as check. A plot
consisted of four, 3-m rows. Spacing was 45cm between rows and 10 em within rows.
Data were analyzed statistically using Genstat Software.
Mean bean grain yield increased significantly with increasing levels of N up to 100 kg N
ha" . Mean seed Fe and Zn concentration increased significantly (P<0.05) with increasing
levels of N up to 100 kg N ha'. In the N trial, highest significant mean yields were
achieved from AND 620 (2807 kg ha-') grown in Kakamega. The same variety grown in
Kabete Field 10 had highest significant mean seed Fe concentrations (137.1 ppm).
Highest significant seed Zn concentrations were obtained from VNB 81010 (36.8 ppm)
grown in Kabete Field 10.
Mean bean grain yield increased significantly with increasing levels of P up to 25 kg P
ha'. Mean seed Fe and Zn concentration increased significantly (P<0.05) with increasing
levels of P up to 50 kg P ha-'. In the P trial, highest significant mean yields were achieved
from GLP 2 (2747 kg ha-I
) grown in Kakamega, while highest significant mean seed Fe
concentrations were obtained from AND 620 (123.4 ppm) grown in Kabete Field 10.
Highest significant increase in seed Zn concentrations were obtained from VNB 81010
(49.1 ppm) grown in Kabete Field 10.
Mean bean grain yield increased significantly with increasing levels of K up to 100 kg K
ha-1• Mean seed Zn concentration increased significantly (P<0.05) with increasing levels
of K up to 150 kg K ha-1• In the K trial, highest significant mean yields were achieved
from MLB 49-98A (2856 kg ha-1) grown in Kabete Field 10. Highest significant seed Zn
concentrations were obtained from VNB 81010 (34.3 ppm) grown in the same field.
Mean bean grain yield increased significantly with increasing levels of lime up to 7 t ha-1
Mean seed Fe and Zn concentration decreased significantly (P<0.05) with increasing
levels of lime. In the lime trial, highest significant mean yields were achieved from GLP
2 (2744 kg ha') grown in Kakamega, while highest significant mean seed Fe
concentrations were obtained from AND 620 (8l.8 ppm) grown in Kabete Field 10.
Highest significant seed Zn concentrations were obtained from VNB 81010 (29.2 ppm)
grown in Kakamega.
Mean bean seed Fe concentration increased significantly (P<0.05) with increasing levels
of soil Fe up to 4 kg Fe ha-1and foliar Fe up to 150 L Fe ha-1
• Mean seed Zn also
increased significantly with increasing levels of soil Fe up to 4 kg Fe ha_1 and foliar Fe up
to 150 L Fe ha-1• In the Fe trial, Highest significant mean seed Fe concentrations were
obtained from AND 620 (152.0 ppm) grown in Kabete Field 10, while highest significant
seed Zn concentrations were obtained from VNB 81010 (33.0 ppm) grown in the same
field.
Mean bean seed Fe concentration increased significantly (P<0.05) with increasing levels
of soil Zn up to 4 kg Zn haland foliar Zn up to 100 L Zn ha'. Mean seed Zn also
increased significantly with increasing levels of soil Zn up to 4 kg Zn ha-1 and foliar Zn up
to 100 L Zn ha -1. In the Zn trial, highest significant mean seed Fe concentrations were
obtained from Maharagi Soja (91.2 ppm) grown in Kabete field 10, while the highest
significant seed Zn concentrations were obtained from VNB 81010 (68.2 ppm) grown in
the same field.
The results obtained indicate that adequate levels ofN, P, K, Fe and Zn have the potential
to increase bean yields, seed iron and zinc concentrations. However adequate levels of
lime increased bean yields, but reduced seed iron and zinc concentrations. N, P, K, Fe
and Zn application would therefore have an added advantage in increasing seed Fe and
Zn concentration in the common bean in order to alleviate micronutrient deficiencies
affecting vast human populations around the world, particularly medium and low income
households in the developing countries, Kenya being one of them. | en |
