Abstract
Two field experiments were carried out under centre-pivot irrigation in central Saudi Arabia during the winter seasons of 1990/91 and 1991/92 to examine the yield and quality responses of wheat to biofertilization with chicken manure at rates of 0, 4.1, 8.25, 16.5 and 33.0 t ha(-1). The response curves obtained for the test measurements as a function of the rate of chicken manure applied indicated that grain yield, grain quality and straw yield were promoted by the rate of chicken manure. The point of profitable grain yield (greatest economic return) corresponded to the manurial rate of 8.25 t ha(-1) (maximum biodegradation). A simplified economic analysis of the data obtained revealed that operating beyond this rate is not advisable since it does not appeal to farmers and may lead to monetary losses. N and P uptake, as a function of chicken manure application rate, increased progressively with an increasing manurial rate. The superiority of the second season over the first one in the magnitude of the test measurements studied was variously attributed to the infection by Fusarium graminearum, causing root and crown rot disease of wheat during the first season and to the higher amount of mineralizable plant nutrients during the second season.