Phosphorus Requirement of Wheat under Chloride and Sulphate Dominated Salinities

摘要

In a greenhouse study conducted on a Typic Torripsamment, wheat was grown up to maturity at three salinity levels (ECe 6, 8 and 10 dS m~(-1)), predominated by either chloride (C1:SO_4=7:3) or sulphate (C1:SO_4=3:7) salts. Each ECe treatment includinga non-saline control (ECe 1.2 dS m~(-1)) was established at four levels of added P (0, 30, 60 and 90 mg P kg~(-1)soil). At salinity level of 6 dS m~(-1) wheat growth at the boot stage was reduced significantly under all P treatments, but grain yield wasreduced only in the low P treatments (0 and 30 mg P kg~(-1) soil). At comparable ECe levels, the external requirement of P was about 50% less under SO_4 than under Cl-dominated salinity, as grain yield as well as P and S uptake at 60 mg P kg~(-1) soil under SO_4 and 90 mg P kg~(-1) soil under Cl-salinity were equal. The external P requirement of wheat also increased with increase in the ECe of soil, as grain yield at 30 mg P kg~(-1) soil at ECe 6 and 60 mg P kg~(-1) soil at ECe 8 under Cl-and 30 mg P kg~(-1) soil at ECe 8 and 60 mg P kg~(-1)soil at ECe 10 dS m~(-1) under SO_4-salinity were comparable. The magnitude of the grain yield response to application of 90 mg P per kg soil relative to zero P increased from 1.8 times in non-saline to 5-7 times under SO_4-salinity and 7-9 times under Cl-dominated salinity.