Understanding Boron transformations in intensive cropping: implications for soil fertility and sustainability

Intensive cropping systems characterized by continuous cultivation and high nutrient uptake can significantly alter micronutrient dynamics. Boron (B) is particularly affected due to its narrow optimal range, high mobility in soil and sensitivity to changes in pH, organic matter, and moisture condition. This study addresses the need to understand boron transformations under various cropping systems for sustainable soil fertility management. The study was conducted in Gurdaspur district, Punjab on Typic Haplustalfs across seven cropping systems: rice-wheat, maize-wheat, sugarcane-sugarcane, mango, litchi, cole crops, and barren lands. Soil was sampled at five depths (0–15 cm to 90–120 cm) and analyzed for boron fractions using a modified sequential extraction method. Residual boron was the most prevalent fraction, accounting (80–87%) of total boron in all cropping systems. Soils under cole crop recorded the highest concentrations of labile B fractions and total B, due to regular farmyard manure application, while barren lands showed the lowest B levels due to minimal organic inputs. Available boron showed a strong positive association with soil organic carbon (r = 0.82), and a negative relationship but significant with soil pH (r = -0.76), reflecting the combined effect of organic matter and soil chemistry on B availability. These findings underscore the critical role of cropping intensity and organic amendments in shaping boron dynamics in soil. To support soil fertility and long-term agricultural sustainability, the study recommends site-specific boron management strategies, including regular soil testing and balanced use of organic and inorganic B sources, particularly in intensively managed cropping systems. Keywords Boron fractionation · Cropping systems · Soil depth · Typic haplustalfs · Soil depth