Optimizing Phosphorus Levels in Wheat Grown in a Calcareous Soil with the Use of Adsorption Isotherm Models

Abstract

Crop response to phosphorous (P) application is often erratic in most soil types in the world. In alkaline calcareous soils, P retention and mobilization take place due to precipitation and adsorption. P adsorption isotherms are the powerful tools for assessing optimum P levels for different crops and soils. Laboratory and field studies were carried out to evaluate P sorption capacity in a highly calcareous soil and corresponding fertilizer levels for yielding 0.1 to 1.0 mg P L −1 of soil solution. Although Freundlich adsorption isotherm model showed a better fit than Langmuir model, P fertilizer levels used in the field, ranging from 20 to 150 kg P 2 O 5 ha −1 , were based on Langmuir model to yield the estimated P solution. Moreover, nitrogen (N) and potassium (K) were applied at the rates of 120 and 60 kg ha −1 as urea and potassium sulfate (K 2 SO 4), respectively, in a basal treatment at the time of sowing. Grains per spike, 1000-grain weight, grain yield, spike length, and biological yield were increased as the level of P increased, but the non-significant differences among 90, 100, and 120 kg P 2 O 5 ha −1 for most of the above parameters suggested that the former rate could be the maximum level for wheat fertilization in the calcareous soil. Similarly, plant N, P, and K were increased with application of P, but non-significant differences were observed from doses 90 to 120 kg P 2 O 5 ha −1. Moreover, the rate of 90 kg P 2 O 5 ha −1 could yield 0.6 mg P L −1 of soil solution as per Langmuir adsorption isotherm model, while as per Freundlich model, this value could reach only 0.3-0.4 mg P L −1 , which is close to the published literature. It is concluded that Freundlich adsorption isotherm is more suitable to be used for the calculation of phosphatic fertilizer rate and its adsorption capacity in the given soil than Langmuir adsorption isotherm.

Integrated use of phosphorus fertilizer and farmyard manure improves wheat productivity by improving soil quality and P availability in calcareous soil under subhumid conditions

“…Furthermore, organic amendments enhance soil biological and enzyme activities and increase organism abundance, thus enhancing P availability through dissolved organic carbon in the soil ( Wu et al., 2013 ). The studied soil was highly calcareous, and the Ca–P was the most abundant fraction in these soils due to the high content of Ca 2+ that forms calcium phosphates with P and hampers the availability of P ( Saeed et al., 2021 ). The organic compounds can decrease the formation of Ca–P due to calcium solubilization by decreasing the soil pH due to the release of organic acids from SOM decomposition ( Kumar et al., 2020 ).…”

“…Plant-available P (AB-DTPA) in these highly alkaline calcareous soils has very low availability due to high fixation, and slow diffusion, thus limiting plant growth and crop yield. The addition of FYM alone or in combination with inorganic fertilizers decreases P fixation owing to the inactivation of Fe and Al ions thus improving the adsorption capacity of P in soil ( Jamal et al., 2018 ; Saeed et al., 2021 ).…”

“…Plants require P as an essential macronutrient to complete their life cycles ( Marschner, 2012 ; Hopkins, 2015 ; Ding et al., 2020 ; Hopkins, 2020 ). In calcareous soils, a majority of applied P fertilizer is adsorbed on the calcite surface and becomes temporarily unavailable to plants, which can cause a yield reduction ( Hopkins, 2015 ; Saeed et al., 2021 ). Plant-available P in soil is affected by soil chemistry properties, especially pH and limestone content ( Lindsay, 2001 ; Fixen and Bruulsema, 2014 ).…”

Coapplication of water treatment residual and compost for increased phosphorus availability in arable sandy soils

“…The Langmuir and Freundlich isotherms were used to understand the relationship between the quantity of P adsorbed per unit soil weight and the concentration of P in the solution. The Langmuir and Freundlich isotherms have often been used to describe P sorption characteristics (e.g., Jeppu & Clement, 2012; Olsen & Watanabe, 1957; Saeed et al, 2021). P adsorption parameters were calculated with the Langmuir isotherm equation $$${C}_{{\rm{e}}}/Q=1/{{bQ}}_{0}+{C}_{{\rm{e}}}/{Q}_{0},$$$where Q is the mass of P adsorbed per unit mass of coamendment (mg kg −1 ), C e the equilibrium concentration of P (mg P L −1 ) in suspension after 24‐h equilibrium, Q 0 the maximum adsorption capacity (mg P kg −1 ) and b a constant related to the binding strength of P at the adsorption sites (L mg −1 P).…”

“…The external P fertilizer requirement (PFR) was calculated based on the assumption that soil should contain 0.2 mg P L −1 in solution for optimum plant growth (Fox & Kamprath, 1970; Roy & De Datta, 1985). The P 2 O 5 fertilizer requirement was calculated based on the method by Saeed et al (2021). Briefly, the method takes into account the targeted P concentration in the equilibrium solution, the MBC and the P bonding energy constant (see Saeed et al, 2021).…”