Effects of salinity, phosphorus fertilizer, and intercropping of wheat with lathyrus, and vetch on available-P and inorganic P fractions in a loamy sand soil

Abstract

In this research, two separate experiments were carried out as factorial on the basis of completely randomized design with three replications. In the first experiment, the effects of cultivation, salinity, and phosphorus (P) fertilizer on available-P and inorganic P fractions were investigated with three factors of cultivation type at six levels (No cultivation, wheat monoculture, lathyrus monoculture, vetch monoculture, wheat-Lathyrus intercropping, wheat-vetch intercropping), P fertilizer at two levels (zero and 80 mg P/kg) and soil salinity (ECe) at two levels (0.75 and 7.5 dS/m) under greenhouse conditions. The second experiment was conducted to investigate the effects of ageing, salinity, and P fertilizer on Olsen-P and inorganic P fractions with three factors of time at two levels (zero and 90 days), P at two levels (zero and 80 mg P/kg), and ECe at two levels (0.75 and 7.5 dS/m) under laboratory conditions. Results showed that the cultivation of wheat, lathyrus, and vetch in both monoculture and intercropping conditions decreased Olsen-P, NH₄F-P, NaOH-P, H₂SO₄-P, and sum of P fractions. Under P using conditions, available-P in the rhizosphere soil was more than the one in bulk soil and in intercroping it was more than the one in monoculture. In 90 days after P using, NaCl salinity decreased NH₄Cl-P, NH₄F-P, and NaOH-P while increased Olsen-P and H2SO4-P compared to non-saline conditions. Aging after P using decreased NH₄Cl-P and Olsen-P and increased NH₄F-P, NaOH-P, and H₂SO₄-P. Under P using conditions, Olsen extractant may underestimate soil P availablity for wheat, lathyrus, and vetch plants at both monoculture and intercropping conditions. Generally, intercropping of wheat-Lathyrus and wheat-vetch and using 80 mg P fertilizer per kg of soil can be recommedded under similar conditions.