Fractions of Copper in Soil under a Long-Term Experiment and Their Contribution to Copper Availability and Uptake by Maize—Wheat Cropping Sequence

ABSTRACT

Soil and plant samples were collected from on-going long-term experiment at Indian Agricultural Research Institute, New Delhi farm to study the distribution of various forms of copper (Cu) and their contribution to availability and plant uptake in maize (Zea mays L.)—wheat (Triticum aestivum L.) sequence. The optimum dose-based treatments selected for the study were nitrogen-phosphorus-potassium (NPK), NPK + Farmyard manure (FYM), NPK+ zinc (Zn) and control (no fertilizer or manure). Uptake of Cu by maize and wheat varied from 17.0 to 37.5 and 60.8 to 149.3 g ha⁻¹, respectively, under different treatments. Copper uptake by wheat was significantly higher under 100% NPK + FYM than that with 100% NPK. There was no significant difference among the treatments with respect to diethylenetriaminepentaacetic acid (DTPA)-extractable Cu in 0–15, 15–30, 30–45, and 45–60 cm soil layers. However, with increasing depth of soil, it showed declining trend under all the treatments. Mean value of total Cu was 28, 32, 25, and 21 mg kg⁻¹ in 0–15, 15–30, 30–45, and 45–60 cm depths, respectively. Major part of the total Cu was present as residual form. Sorbed copper (SORB–Cu) contributed directly towards its availability both in pre-sowing maize and post-harvest wheat soil samples. SORB–Cu and organic matter bound Cu (OM–Cu) contributed directly towards the uptake by the component crops. Copper associated with easily reducible manganese, carbonate, and iron and aluminum oxides were most recalcitrant forms present in soil and their effects on availability and crop uptake were adverse.

Keywords:

• long-term experiment
• Inceptisol
• fractions of copper
• maize-wheat sequence
• Cu availability
• plant uptake

ACKNOWLEDGMENTS

We thank the Indian Agricultural Research Institute, New Delhi and Council of Scientific and Industrial Research, New Delhi, India for providing research facilities and financial assistance. We appreciate the support provided by the staff associated with the long-term experiment at the Institute.