Effect of Mycorrhizal Inoculation on Growth and Nutrient Uptake by Leek (Allium porrum) fertilized with Inorganic N Combined with Saturated Polonite

Abstract: The continuous rise in global population continues to increase the demand for food. Meeting this rise in demand requires an increase in agricultural input, such as applying fertilizers, including phosphorus (P). This results in a surge in demand and acquisition of P from non-renewable phosphate rocks from natural reserves in areas such as Morocco, USA and Russia. Rise in political unrest within Morocco and between Russia and Ukraine pose threats to global trade and supply. Continuous accumulation of P in soil due to P application increases the risk of aquatic eutrophication. Inoculation with arbuscular mycorrhizal fungi (AMF) can potentially improve plant P uptake and reduce fertilizer input dependence. The need to apply principles of the circular economy such that recycled P fertilizers used for crop production are also used responsibly in crop cultivation is crucial for phosphorus-importing countries, sustainable food production, food security and the environment. This study, therefore, aimed to determine the effect of mycorrhizal inoculation on growth, Nitrogen (N) and P uptake by host plant (leek) fertilized with P-saturated polonite combined with either ammonium sulfate or nitrate. The study involved an incubation and a cultivation experiment. The incubation experiment was designed to determine the effect of nitrogen application using three levels of ammonium sulfate (200 mg/pot, 400 mg/pot, and 600 mg/pot), each supplying 50, 100, and 150% of 140mg N/L and ammonium nitrate (370.06 mg/pot) supplying 150% of 140mg N/L on soil pH, and phosphorus availability in the soil and from 9g per pot of saturated polonite (PO) added. The cultivation experiment was designed to determine AMF inoculation on growth and P uptake by leek (Allium porrum) fertilized with 9g of saturated polonite, 400 mg/pot of ammonium sulfate and 247.06 mg/pot of ammonium nitrate per standardized rate of N application (140 mg N/L soil). AMF inoculation significantly and positively influenced above-ground biomass, shoot P concentration and uptake by the plants under (-) PO conditions but did not affect P uptake and P acquisition efficiency (%) under (+) PO conditions. Other nutrients, including potassium, sodium and magnesium, were significantly influenced by AMF inoculation. Saturated polonite addition significantly and positively influenced soil P concentration, plant above-ground biomass, shoot P concentration and uptake. Saturated polonite also significantly increased soil pH compared to control but negatively affected ammonium-N in the soil. Root colonization was positively influenced by AMF inoculation, but there was no correlation observed between root colonization and P uptake. Ammonium sulfate at 100% before incubation and 150% after incubation reduced soil pH compared to control. Nitrogen (N) addition overall affected shoot concentration and uptake of Na, S and Mn. Ammonium sulfate and nitrate positively influenced soil N availability, but did not affect soil P availability and negatively influenced shoot P concentration and uptake compared to control treatment. Ammonium sulfate supplied at 150% (600 mg/pot) reduced soil pH compared to control after incubation. When applied to PO treatments, ammonium sulfate (100%) positively influenced shoot fresh and dry weight compared to ammonium nitrate. The study concluded that AMF inoculation may increase plant growth (above-ground biomass), shoot P concentrations and uptake, but this depends on whether soil P is enough due to P addition or deficiency in the soil. In addition, saturated polonite as a P fertilizer alternative can potentially increase plant growth (above-ground biomass), shoot P concentration and uptake.