Dynamics of AB-DTPA-extractable Zn in high and low limed calcareous soils amended with biochar and farmyard and poultry manures

Abstract

Zinc (Zn) deficiency is widespread in the calcareous soils which needs correction in a sustainable way. An open-air incubation study was conducted to observe the effects of biochar (BC), farmyard manure (FYM) and poultry manure (PM) on ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA)-extractable Zn in high-limed (16.6% CCE) and low-limed (6.6% CCE) calcareous soils. Both soils were treated with10 g kg−1 (equivalent to 20 t ha−1) of BC, FYM and PM and three levels of Zn (as ZnSO4), i.e. 0, 1.5 and 3 mg kg−1 soil. The AB-DTPA-extractable Zn and soil pH was determined at 0, 7, 14, 28, 56 and 84 days of incubation. Results revealed that more extractable Zn was recorded in the low-limed soil as compared with high-limed soil. Further, more extractable Zn was detected in both soils when treated with PM (84.62%), followed by FYM (69.23%) and BC (52.56%) during 0–28 days as compared with control. But after 56 days and later, BC alone or in combination with external Zn produced more extractable Zn. Increase in extractable Zn, upon Zn external application, was dose dependent (highest with 3 mg Zn kg−1 soil) in both soils. Moreover, high-limed soil (0.73–1.28 mg kg−1) had significantly lower AB-DTPA-extractable Zn than low-limed soil (1.28–1.45 mg kg−1) at each incubation interval, irrespective of applied Zn levels. Data of combined application of organic amendments with external Zn showed that PM + Zn treatment had more extractable Zn (1.23–1.44 mg kg−1) than FYM + Zn treatment (1.08–1.32 mg kg−1) in both soils in earlier incubation intervals, but later, more extractable Zn was recorded in BC + Zn treatment (1.39–1.49 mg kg−1) at 84th day of incubation. Further, pH of high- and low-limed soils was decreased with PM, FYM and BC, applied either alone or in combination with external Zn. Thus, organic amendments applied with mineral Zn may improve Zn pools and productivity of calcareous soils in a sustainable way.