Abstract
With advancement of time soil fertility in Bangladesh has declined.
Consequently, micronutrient deficiency has arisen. Increasing cropping intensity
and cultivation of modern varieties with high yield potential are the major
reasons of nutrient depletion from soil, which results in crop yield decline. Three
sets of experiments, one set for delineating soil micronutrient status, another set
for evaluation of crop response to added micronutrients, and the third set for
determination of micronutrient rates for 3-crop patterns were carried out in Old
Meghna Estuarine Floodplain (AEZ 19) soils. Soil analysis of top soils shows that
the Zn and B availability has declined after a decade time. For other
micronutrients, viz. Cu, Mn and Fe, still high status prevails. Micronutrient
levels of subsoil (15-30 cm) were low in general than those of top soils (0-15 cm).
Micronutrients response study was conducted in Chandina upazila of Comilla
district using potato, tomato and brinjal as single crop and cauliflower-maize-T.
aus rice as a cropping pattern. The study comprised seven treatment
combinations including a control following additive trial technique.
Micronutrients were added at the rates of 3 kg Zn, 2 kg B, 2 kg Cu, 3 kg Mn, 5 kg
Fe and 1 kg Mo per hectare. The macronutrients namely, N, P, Kand S were
applied at recommended rates to all plots, and rationale was followed for the
second and third crops. The crops responded significantly to the application of
Zn and B only, not to the Cu, Mn & Fe applications. Thus, micronutrient rate
study was performed with only two micronutrients, Zn and B in the potato-T.
aus-T. aman rice and cauliflower-maize-T. aus rice patterns. Each of the patterns
were tested in two separate sites of the same upazila where second set of
experiments were conducted. The treatments were designed in a manner so that
effects of 1-crop, 2-crop and 3-crop application of Zn and B on the crops would
be known. Application of Zn4B1.5+ZnoBo+ZnoBo or Zn2B1.5+Zn2Bo+ZnoBo
performed better with respect to mainly crop yield and protein & Zn
concentrations of crop produce in a 3-crop pattern. The highest MBCR was also
recorded with Zn4B1.5+ZnoBo+ZnoBo treatment combination. Considering
aforesaid aspects, either of these treatment combinations can be recommended
for a 3-crop pattern but Zn4B1,5+ZnoBo+ZnoBo is the best.