Experience with Direct Drilling in Semiarid Oregon

Don Wysocki, Extension Soil Scientist

Columbia Basin Agricultural Research Center, Pendleton, Oregon

Direct drilling has been used to a limited extent in eastern Oregon cropping systems since the early 1980's. Growers and researchers began experimenting with this method of crop production as a means for reducing tillage and soil erosion. Over the past 20 years, direct drilling has had limited and varied success. Early attempts at direct drilling faced many challenges and questions. These included seed placement, residue clearance, fertility management, fertilizer placement, weed, disease and other pest management, and drill operation on steep slopes. Direct drilling has evolved and improved over time. Presently, many producers have used direct drilling in some fields and in some year after low residue crops. However, very few farms use direct drilling as the sole method of crop production. Machinery investment cost, greater economic risk, and greater complexity in management are reasons that complete direct drill cropping systems have not become more widely used. Through research and grower experience direct drill systems will continue improve. The following discussion covers various aspects of direct drilling that should be considered and/or understood when designing or refining direct drilling systems. Direct drilling should be thought of as just part of an entire cropping system. The various aspects of the system must be considered together to use direct drilling successfully.

Seed Placement: Growers should evaluate their soils, slopes, residue conditions, crop rotations and precipitation when considering direct drill options. All these factors interact to determine the conditions in which a drill must operate. Drills must be capable of placing seed, at uniform depth, in firm contact with moist soil with the proper amount of soil cover. Growers should assess their conditions and select and operate a drill that will achieve this seed placement. Drill options include row spacing, shank or disk openers, residue clearance, press wheel size and composition and other features. The combination of drill options that gives the desired seed placement for the most economical price is the goal. Drill should operate properly on slopes. This includes uniform placement across the drill and minimum slippage downslope.

Weed Management: Managing weeds is important in direct drill systems. In eastern Oregon, downy brome (cheat grass) and goat grass are the most troublesome weeds in direct drilled winter wheat. For this reason, it is advisable to direct drill in fields with light or moderate grass infestations. If weed pressure is high, it is better to direct drill a spring crop to bring the grass problem under control.

Direct drilling of winter wheat has been more difficult when seedbeds remain dry throughout the fall. Under this condition, downy brome and goat grass do not germinate before drilling and there is not an opportunity for control before planting. If conditions remain dry into November, delaying planting until spring should be considered. Winter wheat is almost always more profitable than a spring crop, but it may be better to control winter annual grasses by planting in the spring. Glyphosate should be used whenever grass has emerged prior to planting time. This is particularly important for goat grass control because soil incorporated herbicides are not an option when direct drilling. Some experimentation with surface applied herbicides in direct drill fields in underway, but results are not yet available. With current weed control technologies, rotation to spring cropping when winter annual grass becomes a problem is advisable.

Disease Management: Diseases organisms are present in both conventional planted and direct drilled fields. Generally, the difference is in the environmental conditions for disease to infect the crop. In general, seed placement and fertility are important aspects of disease management. Good seed-to-soil contact is important in initiating a healthy stand. Slightly higher seeding rates may be advisable when seedbed conditions are poor. Maintaining proper fertility near the seedling is important to keep seedlings vigorous and healthy.

Recognizing and diagnosing disease problem are important in direct drilled wheat crops. If you know what diseases to expect and their symptoms it is easier to recognize the problem. For example, delayed planting can be used to control strawbreaker foot rot or Cephalosporium stripe. However delayed planting is not effective against Rhizoctonia or Pythium.

Managing the green bridge is critical in direct drill systems. Both fall and spring applications of Glyphosate should be used to control weeds and volunteer plants to eliminate infections in the crop. When possible and practical, 20 days should be allowed between herbicide application and drilling.

Fertility Management: Fertilizer application rates and placement of materials are important in direct drilling. Just as with conventional systems, soil testing and proper soil sampling should be a part of direct drill systems. Once that level of management is achieved then the specific needs of direct drill systems can be addressed.

Most direct seed drills place fertilizer below or below and to the side of the seed row. Fertility near the seed is critical for healthy vigorous plants. Small amounts of fertilizer placed with the seed are acceptable, but full rates can not applied in this position because of risk to germination. One system that has been used in eastern Oregon is to apply starter fertilizer with the seed and then to apply the remaining nutrition with a spoke-wheel applicator after plant emergence. This allows drills without fertilizer placement capabilities to be used for direct drilling. It also reduces the amount of time needed to fill the drill at planting. These allows drilling to be done more timely.

In the transition from conventional to direct drilling, it appears that nitrogen rates may have to be adjusted upward. At this time the exact amount of additional nitrogen needed is uncertain and may depend on environmental conditions. Generally, an additional ten percent N should be appropriate. However, this should be adjusted according to specific field conditions, past performance, and weather conditions. Also both phosphorus and sulfur nutrition should be carefully managed. When direct drilling spring crops both these nutrients should be placed near the seed.

Crop Rotation: Past experiences with direct drilling of winter wheat have shown that annual grassy weeds and/or cereal root disease can become a problem. For these reasons, crop rotations seem essential to developing direct drilling systems. The objective should be to keep winter wheat in the rotation as much as possible (for profitability reasons), but to rotate to other crops for the purpose of sanitation. Rotation crops can be other winter crops such as winter Canola, or spring crops, including cereals, yellow mustard, Canola or legumes. The choice of these crops depends on local rainfall and the types of pest problems. Intensifying and diversify the rotation should be the general strategy to maintain profitability and eliminate pest problems. Direct drilling should be a method to conserve water and reduce the amount of fallow in any rotation. The additional water saved and the reduced workload should enable growers to intensify the rotation. Diversity (number of different crops grown) seems essential to provide the sanitation needed to maintain healthy direct drill systems. In the past, few complete direct drill systems have succeeded because sanitation problems developed and crop rotation was not feasible or was just not practiced.

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