Phosphorus requirements of cereal crops and fertility build up factor in a typic camborthid soil

Abstract

Field studies were conducted to arrest Phosphorus requirements of wheat, sorghum fodder and rice crops at 95% relative yield; Phosphorus Fertility Buildup Factor (PFBF) and level of phosphorus buildup in a Typic Camborthid (Sultanpur series) soil of rice tract of the Punjab, Pakistan. Sorption isotherms were constructed in the laboratory and data was fitted into linear form of modified Freundlich Model and doses were computed against soil solution P levels. Different theoretical P doses were applied in the field to develop soil solution P level of 0.01, 0.02, 0.03, 0.04, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.40 and 0.50 mg L-1 along with a control (native soil solution P). Phosphorus was also applied at the rate of 60 and 90 mg P2O5 kg-1 to subsequent sorghum fodder and rice crops, respectively. Wheat grain and straw, fresh sorghum fodder, rice paddy and straw yields were recorded at the harvest. Plant sampling was done at booting stage of wheat and rice and at the harvest of each crop. Soil sampling was also done at the harvest of each crop. The results indicated that maximum wheat grain yield was 4.05 Mg ha-1; sorghum fresh fodder yield was 43.83 Mg ha-1 and rice paddy yield was 4.43 Mg ha-1. Total P uptake by wheat, sorghum and rice was 22.73, 37.69 and 20.48 kg ha-1, respectively. Mean phosphorus fertility build-up factor (mg P required to build 1 mg P kg-1 soil) was 16.23 and the level of P buildup (mg P kg-1 built-up in soil for each mg P kg-1 soil applied) was 0.062. Level of P depletion was 0.141 mg P kg-1 for NPK check plots while 0.162 mg P kg-1 for P check plots. Internal P requirement for wheat was 0.255% at booting stage and 0.281% for grain stage. For sorghum fodder, internal P requirement was 0.233% and for rice, it was 0.146% at booting stage and 0.266% for paddy stage. © 2007 Asian Network for Scientific Information.