Dynamics of secondary nutrients in an acid alfisol under long term application of fertilizers fym and lime in maize wheat cropping system

Abstract

The intensive cultivation of high yielding varieties and long-term application of secondary nutrient free NPK fertilizers, coupled with lack of addition of any amendment tend to deplete the secondary nutrient reserves in soil affecting the sustainability of agricultural systems. Therefore, the present study was conducted during 50th and 51st cropping cycles from kharif 2022 to rabi 2023-24 in the ongoing Long-Term Fertilizer Experiment which is in progress since rabi 1972-73, to examine the dynamics of secondary nutrients in an acid Alfisol under long-term application of fertilizers, FYM and lime in maize-wheat cropping system. The results revealed that the treatment comprising 100 per cent NPK plus FYM resulted in the highest grain yield of maize (61.39 and 58.14 q ha-1 during 2022 and 2023, respectively) and wheat (27.78 and 26.22 q ha-1 during 2022-23 and 2023-24, respectively), which was at par with combined application of 100 per cent NPK and lime. Continuous omission of potassium and sulfur reduced maize and wheat productivity significantly, whereas, sole application of 100 per cent N resulted in zero yield of both the crops. Additionally, the conjoint application of 100 per cent NPK with FYM or lime resulted in significantly higher nutrients uptake by both the crops compared to other treatments. Furthermore, the long-term application of optimal doses of NPK along with FYM or lime improved the SOC, CEC, available nutrients status across all the soil depths. The integrated application of 100 per cent NPK and lime improved the soil pH compared to initial value. Compared to surface layer, the deeper soil layers showed lower values of soil properties except soil pH. The application of super optimal dose of NPK and conjunctive use of optimal dose of NPK fertilizers and FYM or lime resulted in significantly higher values of fractions of S, Ca and Mg than rest of the treatments, in all soil depths (0-0.15 m, 0.15-0.30 m and 0.30-0.45 m). Whereas, the contents of all these fractions were recorded lower in 100 per cent N alone (T7), 100 per cent NPK (-S) (T9) and control (T11) compared to rest of the treatments. The correlation studies revealed that all fractions of S, Ca and Mg were significantly and positively correlated with each other. The available form of S and exchangeable Ca and Mg were significantly and positively correlated with their respective fractions. Furthermore, all fractions of S, Ca and Mg showed a significant and positive correlation with yield and uptake of respective nutrient by maize and wheat. Conclusively, the continuous cropping without replenishment of plant nutrients and imbalanced application of fertilizers led to depletion of secondary nutrients under maize-wheat cropping system. This study highlighted the importance of FYM or lime addition in combination with chemical fertilizers (NPK) for higher productivity and improvement of soil pH, SOC, CEC, available macro and micronutrients and enriching different pools of S, Ca and Mg in soil. newline