nitrogen, occasional tillage, sorghum, winter wheat


Occasional tillage ahead of winter wheat planting could alleviate herbicide-resistant weeds, redistribute soil acidification, and improve seedbed at wheat planting. The objec­tive of this study was to determine occasional tillage and nitrogen (N) fertilizer ap­plication effects on winter wheat, and grain sorghum yields and soil quality in a wheat-sorghum-fallow cropping system. Treatments were three tillage practices: 1) continuous no-tillage (NT); 2) continuous reduced-tillage (RT); and 3) single tillage operation every 3 years (June-July) ahead of winter wheat planting [occasional tillage (OT)]. The sub-plot treatments were assigned to four N fertilizer rates (0, 40, 80, and 120 lb/a of N). Results showed tillage had no effect on winter wheat grain yield. Averaged across the 2 study years, wheat yields were 29.4 bu/a with NT, 31.0 bu/a with RT, or 31.6 bu/a with OT. Applying N fertilizer increased wheat yield, ranging from 20 bu/a with no N fertilizer to 38.7 bu/a when N fertilizer was applied at 120 lb/a of N. How­ever, tillage (P= 0.04) and year × N rate interaction (P= 0.003) had significant effect on grain sorghum yield. Average grain sorghum yield with RT (73.6 bu/a) was less than NT (79.4) or OT (75.4 bu/a). Averaged across tillage and years, sorghum grain yield was 60.3 bu/a with no N fertilizer and 86.8 bu/a when N was applied at 120 lb/a of N. In most years, sorghum and winter wheat grain yields obtained with 80 lb/a of N were not different from those with 120 lb/a of N, suggesting 80 lb/a of N may be adequate for both crops.


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