Twenty—eight years long chemical fertilization effects on soil potassium status under rice-wheat-green gram cropping sequence

ABSTRACT

A long-term experiment was initiated on potassium (K)-rich clay soils in a rice-wheat-green gram cropping sequence to assess the feasibility of K fertilizer recommendation. Treatment consists of absolute control, farmyard manure to rice (25 t ha⁻¹), 50% nitrogen and phosphorus (NP), 100% NP (257:160 kg NP ha⁻¹), 50% NPK (Nitrogen, Phosphorus and Potassium), 100% NPK (257:160:135 kg NPK ha⁻¹), NP (257:127 kg NP ha⁻¹) and NPK (257:120:67 kg NPK ha⁻¹) as per soil test, 50% N, 100% N (257 kg N ha⁻¹) to the sequence. NP and NPK application as per soil test significantly increased the yield of rice (4.15 and 3.92 t ha⁻¹), wheat (2.59 and 2.56 t ha⁻¹), green gram (0.66 and 0.62 t ha⁻¹) and rice equivalent yield (8918 and 8660 kg ha⁻¹) and net returns (1018 and 959 US $ ha⁻¹), respectively. Sustainable yield index for rice, wheat and green gram was 0.53–0.63, 0.32–0.45 and 0.10–0.23, respectively. Apparent nutrient balance for N (38.7–120.9 kg ha⁻¹) and P (43.6–113.5 kg ha⁻¹) was positive and negative for K (−34.9 to −154.8 kg ha⁻¹). Residual water-soluble (3.3 and 4.0 mg kg⁻¹), exchangeable (84.2 and 95.1 mg kg⁻¹) and available K (87.2 and 98.9 mg kg⁻¹) were higher with full K dose.

KEYWORDS:

• Rice-wheat-green gram
• soil potassium
• nutrient balance
• yield trend
• potassium fraction

Acknowledgements

We thank all scientists who have handled this long-term experiment from its beginning to its end and who have given their valuable research contributions to this experiment. Also thankful to Dr Sushanta Saha, BCKV, Kalyani, India, for his help in statistical analysis.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Navsari Agricultural University, Navsari, Gujarat