Soil boron dynamics as influenced by NPK levels in oil pam plantations under tropical conditions

Abstract

Boron (B) is the micronutrient very much essential for stability of cell wall, viability of pollen grains, pollen germination, pollen tube growth, and development of fruits and seeds. However, it was found to be the limiting nutrient in oil palm plantations in India. B interacts with other nutrients synergistically or antagonistically. There is a need to study the B fractions and their association with other nutrients for efficient B management. The soil samples (0- to 60-cm depth) of nutrient management trial with graded levels of N (0, 1200, 2400 g N palm⁻¹ year⁻¹), P (0, 600, 1200 g P₂O₅ palm⁻¹ year⁻¹), and K (0, 600, 1200 g K₂O palm⁻¹ year⁻¹) were collected and analyzed for pH, electrical conductivity, organic carbon (OC), nutrient content, and B fractions. The majority of B fractions were residual boron (RSL-B), which constituted 73.3%–93.8% of total B. In contrast, the plant-available B fractions (readily soluble B [RDS-B] and specifically adsorbed boron [SAD-B]) accounted for <2.0% of the total B content. The oxide bound boron (OXD-B) accounted for 2.35%–8.18%, whereas the organically bound boron (ORG-B) constituted 1.25%–20.1% of total B. Fractions of B were significantly influenced by the dose of primary nutrients. The plant accessible B fractions were positively influenced by soil parameters like soil reaction, OC, and available nitrogen (N), whereas OXD-B was negatively associated with available phosphorus (P). Considering the relationship within B fractions, SAD-B and ORG-B showed a positive correlation with RDS-B, indicating their involvement in replenishment of plant-available B pool. The study suggests that application of 1200 g N, 600 g P₂O₅, and 600 g K₂O significantly increased the plant-available B fractions in soils of oil palm plantations. The information generated from the study aids in efficient management of B.