Effect of P fertilization on yield and quality of oat (Avena sativa L.) fodder on two different textured calcareous soils

Oat is an important fodder for animals in Pakistan. Phosphorus is a quality nutrient for fodders. The use of P for oat is negligible. Thus a field study was conducted to evaluate the effect of P fertilizer on yield and quality of oat fodder on sandy clay loam and loamy sand calcareous soils. Sorption isotherms were constructed by equilibrating 2.5 g soil with 25 mL of 0.01 M CaCl2 solution containing 0, 20, 40, 60, 80, 100, 200, 300, 400 and 500 µg P mL -1 as KH2PO4 and shaking for 24 hour. Against theoretical soil solution P levels of 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, and 0.50 mg P L -1 , fertilizer doses for oat (fodder) were computed by using empirically derived Freundlich equation. It was noted that P adsorption increased but percent marginal adsorption of P decreased by increasing its level of application in both the soils. P adsorption was more in sandy clay loam soil (88.30%) than loamy sand soil (80.42%) at the lowest P application rate of 20 mg kg -1 . At the highest rate of P application (500 mg P L -1 ) percent adsorption of P was 44.38% in sandy clay loam soil and 29.12% in loamy sand. Different P fertilizer doses were required for different soils to develop the same level of solution P. Maximum oat fodder yield and dry matter contents obtained were 41.48 t ha -1 , 20.21% at 0.30 mg P L -1 from sandy clay loam soil and 17.87 t ha -1 , 16.65% at 0.25 mg P L -1 from Loamy sand soil. P concentration, crude protein, crude fiber