Abstract: Application of biogas sludgein soil for optimal wheat cultivation was investigated. Pig manure collected from large-scale hog farms was fermented prior to using as fertilizer to compare with the chemical agentcommonly used by local farmers. Variedbiogas slurry application rates were applied to evaluate the growth and grain yield of the wheat in the field. It was found that the plant leavesbecame greener and SPAD value heightened at higher sludge addition rates. At rates rangingbetween 450 t·hm^-2and 600 t·hm^-2, the photosynthetic characteristics, such as Gs, Pn, Ci and Tr, of the plants were high. And, the plant height, stem diameter, and shoot dry weight at the grain filling stage increased by 3.1%, 11.7%, and 9.8%, respectively, over those of control that was chemically fertilized, as the rate reached 600 t·hm^-2. In addition, the panicle number per unit area and the grain count per panicle significantly increased, and the grain yield increased by 8.1%-8.9%. However, beyond that addition level, the photosynthesis of the wheat plantsdeclined and the grain maturationdelayed, which ill-affectedthe crop rotation, as well as the filling, 1 000 grain weightand quality of the grains.