Dryland farming began in eastern Oregon and the Pacific Northwest slightly more that 100 years ago. Over time, farming methods and agronomic practices have changed quickly and often, as new technologies and new ideas appeared. The rate of change has been phenomenal. Within memory, agriculture has gone from intensive human labor and animal power to a highly mechanized and technology based system. Farmers, scientists and the agricultural industry will continue to test new technologies and adopt new ideas. Those that are successful will be rapidly adopted, those that are not, will be discarded. Successful changes will be adopted because they increase production efficiency or economy. Simply speaking this means that new practices must lower cost and/or increase production or provide some other benefits to the producer and society.

Two aspects of dryland farming that are seeing rapid change and innovation are tillage operations and crop rotations. Historically, tillage and summer fallow have been key management practices on PNW wheat lands. Originally, tillage was used to control weeds, reduce crop residues and prepare seedbeds. Fallowing was practiced to distribute labor, conserve water, control weeds, and mineralize soil nutrients. Advancements in equipment, machinery, plant genetics, and fertilizer and chemical technologies are changing how tillage and summer fallow are and will be used. Currently, producers are challenged to remain economically competitive while protecting soil and water resources. To achieve these goals, producers have sought to lessen how often and how vigorously fields are tilled. Fewer and lighter trips over the field reduces cost, conserve soil water, and leave more crop residues on or near the surface to prevent soil erosion. Likewise, if land can be cropped more frequently without fallow, producers should have higher net production and profits. As growers strive to adjust tillage and fallowing practices, numerous questions arise. Fertilizer and tillage management decisions are being made with little previous experience. Two commonly asked questions are "Should I prepare my fields in the fall?" and "Should I fertilize in the fall or wait until planting?".

We investigated the interaction of fertilizer timing, crop rotation, and tillage practices in a spring wheat cropping system. We compared the performance of spring wheat following spring Canola or spring wheat, with and without fall disking, using fall or spring fertilizer application (Table 1).

Adjacent areas that had grown spring Canola (1200 lb/ac yield) and spring wheat (50 bu/ac yield) were prepared in the fall of 1997. Specific tillage or fertilizer operations were applied to achieve the experimental variables (Table 2). Six replications of each treatment were established in the trial. Each tillage plots was 28 X 48 feet. Half of each tillage plot received N fertilizer in the fall, with the remaining half fertilized in the spring. Consequently individual plots of each treatment after sowing were 24 X 28 feet. Fall disking was done with a Sunflower offset disk (26" dia. disks, 3" concavity) pulled 4-inches deep at 4 mph. Nitrogen fertilizer was applied using a spike wheel injector. Plots were seeded using a direct seed Flexicoil 5000 drill equipped with stealth openers. Starter fertilizer was placed below the seed row with the stealth openers.

Plots were harvested in late July using a Hege 140 plot combine. Yields and test weights were determined (Table 3). Samples were taken for grain protein analyses. At this time, protein results have not yet been obtained from the laboratory. Treatments did not influence test weights. Yield was influenced most by the effect of the previous crop. Yields averaged 38.7 bu/acre when wheat followed Canola, but only 34.5 bu/acre when wheat followed wheat. This is slightly more than a 10 percent yield increase after Canola. The rotation effect could be due to several factors. Among these are disease suppression, nitrogen mineralization and immobilization, or available water. Fall disking and fertilizer timing had no effect on yields after Canola, but did influence yields when wheat followed wheat. When wheat followed wheat, disking in the fall increased yields by 2.9 bu/acre or about 8 percent. When wheat followed wheat, fall disking influenced fertilizer timing. In this situation spring nitrogen application resulted in a 2.3 bu/acre yield increase or about 6 percent.

DspropDW.doc