Influence of phosphorus on the tolerance of table pea to chloride and sulfate salinity in a sandy soil

Abstract

Abstract In a greenhouse study, table pea (Pisum sativum L.) was grown from sowing to maturity in Cl‐‐dominated (Cl‐ : SC2‐ 4 = 7:3) and SO2‐ 4‐dominated (Cl‐ : SO2‐ 4 =3:7) saline sandy soil (Typic Torripsamments) at comparable electrical conductivities (ECe 4, 6, and 8 dS m‐1). Each salinity treatment, including the nonsaline control, contained four levels of added P (0, 20, 40, and 80 mg P kg‐1 soil). In P control (Olsen's P 3.5 mg kg‐1), grain yields at ECe 4, 6, and 8 dS m‐1 were 58, 17, and 7% in Cl‐‐dominated salinity and 91, 48, and 37%, respectively, in SO2‐ 4‐dominated salinity. At 20 mg P kg‐1 level (Olsen's P 13 mg kg‐1), grain yields for the respective ECe values were 108, 49, and 13 % in Cl‐‐dominated salinity and 138, 106, and 75% in SO2‐ 4‐dominated salinity, whereas at 80 mg P kg‐1 level (Olsen's P 46 mg kg‐1) yields were 140, 80, and 17% in Cl‐‐dominated salinity and 100, 108, and 128% in SO2‐ 4‐dominated salinity relative to the nonsaline soil. The P requirement at ECe 6 dS m‐1 was twice that of the nonsaline soil in Cl‐‐dominated and equal to that of the nonsaline soil in the SO2‐ 4‐dominated salinity. However, at ECe 8 dS m‐1, the indicator crop did not respond to P level in Cl‐ ‐dominated salinity, while in SO2‐ 4 ‐dominated salinity, its requirement for P was twice that of the nonsaline soil. As the response to applications of P decreased with the increase in Cl content of soil, it appeared that P enhancement of salinity tolerance depended on a certain threshold value of Cl content in the root zone, which was 50 mmol L‐1 for table pea. The deleterious effect of Cl‐ ‐dominated salinity at ECe 8 dS m‐1 (Cl‐ = 73.5 mmol L‐1), irrespective of the P content of soil, appeared to be due to excessive accumulation of Cl (over 6%) and a sharp reduction (54–78%) in the S content of straw, possibly due to the impedence in the translocation of S by Cl at the root‐shoot interphase. Plants grown in Cl‐‐dominated salinity also had considerably less K, Mg, and Na, but more Ca and N in their straw than those grown in SO2‐ 4 ‐dominated salinity.