Soil Calcium, Magnesium and Potassium Status: Concern for Rice Production in Bangladesh under Unfavorable Ecosystems

Unfavorable ecosystems in Bangladesh are under intense pressure of crop production and climate
change impact; although the relationships of indigenous soil nutrients ratios with crop performance
are yet to be fully explored. Experiments were conducted under submergence and cold prone areas
(agricultural ecological zone, AEZ-3), drought and cold prone areas (AEZ-26), non-saline tidal flood
ecosystem (AEZ-13), char and saline prone ecosystem (AEZ-18) and haor ecosystem (AEZ-21) for
evaluating rice grain yield with native nutrients ratios. Synergistic and antagonistic relationships were
observed in different AEZ depending on indigenous nutrient ratios. The K:Ca and K:Mg ratios were
playing significant negative role in AEZ-18 for wet season rice yield; but K:Ca played synergistic role
in AEZ-3 and AEZ-26. In dry season, K:Ca ratio was acting antagonistically in AEZ-3 and AEZ-13 and
K:Mg in AEZ-13. The ratio of K to Ca was acted positively for dry season Boro rice production in AEZ-
18 and AEZ-26. Similarly, K:Mg ratio was playing synergistic role for Boro rice yield in AEZ-3, AEZ-18
and AEZ-26. Application of fertilizers improved dry season rice yield significantly in all AEZ except
AEZ-18 compared to indigenous soil fertility. It is concluded that indigenous soil nutrient ratios play a
vital role in improving rice yield under unfavorable ecosystems in which more K fertilizer need to be
applied for satisfactory rice yield in dry season.