Improvement of Physical and Chemical Properties of Calcareous Dark Gray Soil Under Different Nitrogenous Fertilizer Management Practices in Wetland Rice Cultivation

Soil is a valuable natural resource and medium for plant growth. Modern approaches to agricultural production can have negative impacts on soil health through interventions such as injudicious fertilizer application, tillage operations, and pesticide applications. The aims of this study were to explore whether nitrogen (N) fertilizer management could contribute to improved soil health in degraded calcareous dark gray soils in the northern part of Bangladesh. We investigated the effect of applying N as different fertilizer options (1) Zero N, (2) recommended dose (180 kg ha−1) prilled urea (PU) N, (3) recommended dose plus 25% extra prilled urea (PU) N, (4) 25% minus of recommended dose prilled urea (PU) N, (5) recommended dose in 2 metric ton ha−1 (MT ha−1) cow dung with prilled urea (PU) N, (6) Urea super granule (USG) deep placement and (7) 4 MT ha−1 biochar with recommended prilled urea (PU) N. In our experiment, we observed that fertilizer management options using biochar (4 MT ha−1) with the recommended rate of PU N and cow dung N (2 MT ha−1) supplemented with PU N contributed to the maintenance of good such as physical and chemical properties of soil. After three years of experimentation, the proportion of sand particles in the experimental soil was reduced slightly. On the other hand, the proportion of silt and clay particles increased due to the application of cow dung N 2 MT ha−1 supplemented with PU N and biochar 4 MT ha−1 with recommended PU N. The combined application of cow dung and biochar with fertilizer N significantly increased soil organic matter (1.79 and 1.38% where the initial value was 1.20%) and total N content (0.07–0.09%). The addition of biochar in the soil increased the soil pH (7.62‒8.60). The available phosphorus and exchangeable potassium were improved in the soil due to application of cow dung and biochar. Likewise, the zinc content of the post-harvest soil also increased. Therefore, the application of biochar 4 MT ha−1 with recommended prilled urea N and cow dung N 2 MTha−1 with supplemented prilled urea N are the two good options for restoration or improvement of soil physical and chemical properties.