Determination of critical limit of soil phosphorous for mustard (<i>Brassica napus</i> L.) and maize (<i>Zea mays</i> L.) in different agroecological zones of Bangladesh

Abstract

The idea of a critical limit (CL) of nutritional elements distinguishes deficiency from adequacy, which could suggest fertilizer administration. The critical limit can be used to distinguish between responsive (deficiency) and non-responsive (sufficiency) sites. The study aims to estimate the critical limit of phosphorus (P) for mustard and maize in different Agro-ecological Zones (AEZs) of Bangladesh. In this context, the study was conducted in 20 types of soil and two crops (maize and mustard) both in pot and field experiments. Twenty soils from different places were used as experimental materials, among them 12 soil samples had inadequate soil fertility, 4 had low fertility, and the remaining 4 had medium levels of fertility. The treatments were two crops: BARI Hybrid Maize 7 (Maize) and BINA Sharisha 9 (Mustard) and two levels of phosphorus (P): 0 and 15 ppm. Dry matter (DM) yield was calculated and the nutritional content of plant samples was determined. Depending on the chemical properties of the soil, the results ranged from extremely low to very high levels. Reading the mustard crop, the estimated critical levels of P were found to be 14.8 ppm (graphical) and 18.9 ppm (statistical). Regarding the maize crop, the estimated critical P levels were found to be 14.5 ppm (graphical) and 12.3 ppm (statistical). When soil P is less than the CL, plants respond to P-based fertilizer effectively. The results of the trials will assist in managing P fertilizer for the sustainability of maize and mustard production in diverse soil types in different agroecological zones of Bangladesh.