A COMPARISON OF 3 FALLOW MANAGEMENT STRATEGIES FOR THE LONG-TERM PRODUCTIVITY OF WHEAT IN NORTHERN NEW-SOUTH-WALES

Four experiments were commenced after a 1980 wheat crop, and a fifth a fter the 1981 crop, at different sites representing the major soil typ es of northern New South Wales in the 550-700 mm rainfall zone, to exa mine the influence of 3 fallow management practices [no tillage (NT); stubble retention after harvest, cultivation (SM); stubble burning aft er harvest, cultivation (SB)] on wheat production. Data considered in this paper cover the continuous wheat subtreatments of the 5 experimen ts (1981-90). Nitrogen applied at 50 kg N/ha in addition to the basal treatment was included as a treatment from 1986 to 1988. Across all si tes and seasons, grain yields were in the order SB>SM approximate to N T, stubble retention having a greater effect than tillage. In some yea rs at some sites, differences in grain yield and grain N yield were no t significant. In others, when significant yield differences occurred, variations in grain yield and grain N yield were highly correlated wi th differences in soil N available for the crop. The data show that th e influence of fallow management interacted with season and crop nutri tion, and required long-term study for proper assessment.